U.S. patent application number 15/960594 was filed with the patent office on 2018-11-22 for fiber optic connector with polymeric material between fiber end and ferrule end, and fabrication method.
The applicant listed for this patent is Corning Research & Development Corporation. Invention is credited to Chenueh Abongwa Florian Lohse, Michael Wimmer.
Application Number | 20180335580 15/960594 |
Document ID | / |
Family ID | 62245514 |
Filed Date | 2018-11-22 |
United States Patent
Application |
20180335580 |
Kind Code |
A1 |
Lohse; Chenueh Abongwa Florian ;
et al. |
November 22, 2018 |
FIBER OPTIC CONNECTOR WITH POLYMERIC MATERIAL BETWEEN FIBER END AND
FERRULE END, AND FABRICATION METHOD
Abstract
A fiber optic connector includes polymeric material arranged
within a front end portion of at least one internal bore of a
ferrule. At least a portion of the polymeric material extends from
a terminal end of at least one optical fiber to at least a front
end of the ferrule. A polymeric material end face serving as a
conduit for transmitting optical signals to and/or from the at
least one optical fiber. Waveguiding regions may be incorporated in
polymeric material assemblies. Polymeric material may be printed,
dispensed, or otherwise applied over the terminal end of the at
least one optical fiber in the at least one internal bore, and
subsequently cured. Polymeric material arranged over (e.g., in
contact with) the terminal end of an optical fiber may reduce or
eliminate the need for fiber end face polishing, and creates
physical contact through an optical interface without exerting
undue mechanical stresses on the optical fiber.
Inventors: |
Lohse; Chenueh Abongwa Florian;
(Berlin, DE) ; Wimmer; Michael; (Berlin,
DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Corning Research & Development Corporation |
Corning |
NY |
US |
|
|
Family ID: |
62245514 |
Appl. No.: |
15/960594 |
Filed: |
April 24, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62508083 |
May 18, 2017 |
|
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15960594 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G02B 6/3885 20130101;
G02B 6/3826 20130101; G02B 6/3847 20130101; G02B 6/4239 20130101;
G02B 6/3861 20130101; G02B 6/262 20130101; G02B 6/382 20130101 |
International
Class: |
G02B 6/38 20060101
G02B006/38 |
Claims
1. A fiber optic connector comprising: a ferrule including a front
end, a rear end, and at least one internal bore extending between
the front end and the rear end; at least one optical fiber
extending through the rear end of the ferrule into the at least one
internal bore, the at least one optical fiber including a terminal
end positioned between the front end and the rear end of the
ferrule; and at least one polymeric material arranged within the at
least one internal bore of the ferrule at least in front of the
terminal end of the at least one optical fiber and extending to at
least the front end of the ferrule.
2. The fiber optic connector of claim 1, wherein the terminal end
of the at least one optical fiber is spaced from the front end of
the ferrule by a distance in a range of from about 0.5 .mu.m to
about 50 .mu.m.
3. The fiber optic connector of claim 1, wherein: the at least one
internal bore of the ferrule comprises a front end portion arranged
proximate to the front end and a medial portion arranged proximate
to the front end portion; the medial portion comprises a first
average diameter; and the front end portion comprises a second
average diameter that exceeds the first average diameter.
4. The fiber optic connector of claim 3, wherein the front end
portion of the at least one internal bore comprises a conical or
frustoconical shape having a maximum diameter at the front end of
the ferrule.
5. The fiber optic connector of claim 1, wherein the at least one
polymeric material protrudes outward from the front end of the
ferrule.
6. The fiber optic connector of claim 1, wherein the at least one
polymeric material comprises a plurality of protrusions that extend
outward from the front end of the ferrule.
7. The fiber optic connector of claim 6, wherein the plurality of
protrusions comprises a first protrusion of a first length and a
second protrusion of a second length that differs from the first
length.
8. The fiber optic connector of claim 1, further comprising an
adhesive material positioned between the at least one polymeric
material and at least one of (i) the ferrule or (ii) the at least
one optical fiber.
9. The fiber optic connector of claim 1, wherein the terminal end
of the at least one optical fiber is unpolished.
10. The fiber optic connector of claim 1, wherein the at least one
polymeric material comprises an outer polymeric material layer and
at least one inner polymeric material layer arranged between the
outer polymeric material layer and the terminal end of the at least
one optical fiber.
11. The fiber optic connector of claim 10, wherein the outer
polymeric material layer or the at least one inner polymeric
material layer comprises one or more of the following: a scratch
resistance layer, an anti-static layer, an anti-reflectance layer,
or a lens layer.
12. The fiber optic connector of claim 1, wherein the ferrule
comprises a multi-fiber ferrule, the at least one internal bore
comprises a plurality of internal bores, and the at least one
optical fiber comprises a plurality of optical fibers, wherein each
optical fiber of the plurality of optical fibers extends into a
corresponding internal bore of the plurality of internal bores.
13. The fiber optic connector of claim 1, wherein the at least one
optical fiber comprises a glass material, and wherein the at least
one polymeric material comprises a modulus of elasticity that is no
greater than about 80% of a modulus of elasticity of the glass
material of the at least one optical fiber.
14. The fiber optic connector of claim 13, wherein the at least one
polymeric material comprises an inorganic-organic hybrid
polymer.
15. The fiber optic connector of claim 14, wherein the
inorganic-organic hybrid polymer of the at least one polymeric
material comprises at least one of the following properties:
inorganic-organic hybrid polymer is UV-curable; the
inorganic-organic hybrid polymer comprises polymerizable moieties,
or the inorganic-organic hybrid polymer comprises a functional
group enabling photo-induced curing.
16. The fiber optic connector of claim 1, wherein: the at least one
polymeric material comprises a waveguide material having a first
refractive index and a surrounding material having a second
refractive index that differs from the first refractive index; and
the waveguide material is shaped into at least one waveguide region
that extends between the terminal end of the at least one optical
fiber to an outer end face of the at least one polymeric material,
and wherein the at least one waveguide region is laterally embedded
in the surrounding material.
17. The fiber optic connector of claim 1, wherein: the at least one
optical fiber comprises a multi-core optical fiber; and the at
least one polymeric material protrudes outward from the front end
of the ferrule to define a plurality of compression spots, wherein
each compression spot of the plurality of compression spots is
substantially registered with a different optical fiber core of the
multi-core optical fiber.
18. The fiber optic connector of claim 1, wherein: the at least one
optical fiber comprises a multi-core optical fiber defining a
plurality of optical fiber cores; the at least one polymeric
material comprises a waveguide material having a first refractive
index and a surrounding material having a second refractive index
that differs from the first refractive index; and the waveguide
material is shaped into a plurality of waveguide regions, wherein
each waveguide region of the plurality of waveguide regions extends
between a terminal end of a different optical fiber core of the
plurality of optical fiber cores to an outer end face of the at
least one polymeric material, and wherein each waveguide region is
laterally embedded in the surrounding material.
19. A method for fabricating a fiber optic connector including a
ferrule that has a front end, a rear end, and at least one internal
bore extending between the front end and the rear end, the method
comprising: inserting at least one optical fiber through the rear
end of the ferrule into the at least one internal bore; positioning
a terminal end of the at least one optical fiber between the front
end and the rear end; applying at least one polymeric material to a
front end portion of the at least one internal bore to cause the at
least one polymeric material to extend from a location in front of
the terminal end of the at least one optical fiber to at least the
front end of the ferrule; and curing the at least one polymeric
material.
20. The method of claim 19, wherein said positioning includes
securing the at least one optical fiber to the ferrule with an
adhesive material arranged between the at least one optical fiber
and the at least one internal bore, and the method further
comprises: applying the adhesive material to the at least one
internal bore prior to said inserting of the at least one optical
fiber; causing a leading end of the at least one optical fiber
inserted into the at least one internal bore to extend beyond the
front end of the ferrule; and processing the leading end of the at
least one optical fiber to yield said terminal end of the at least
one optical fiber; wherein said positioning of the terminal end of
the at least one optical fiber includes retracting the terminal end
to a position within the ferrule between the front end and the rear
end.
21. The method of claim 19, wherein said curing of the at least one
polymeric material comprises impinging laser emissions on the at
least one polymeric material.
22. The method of claim 19, wherein said curing of the at least one
polymeric material comprises at least one of a photonic, thermal,
or chemical interaction with the at least one polymeric
material.
23. The method of claim 19, wherein the at least one polymeric
material comprises an outer polymeric material layer and at least
one inner polymeric material layer, and said applying of the at
least one polymeric material to the front end portion of the at
least one internal bore comprises applying the at least one inner
polymeric material layer to the front end portion of the at least
one internal bore with the at least one inner polymeric material
layer in contact with the terminal end of the at least one optical
fiber, followed by applying the outer polymeric material layer over
the at least one inner polymeric material layer.
24. The method of claim 19, wherein: the at least one polymeric
material comprises a waveguide material having a first refractive
index and a surrounding material having a second refractive index
that differs from the first refractive index; and said applying of
the at least one polymeric material and said curing of the at least
one polymeric material include applying of at least a portion of
the waveguide material and curing of the at least a portion of the
waveguide material to form at least one waveguide region that
extends between the terminal end of the at least one optical fiber
to an outer end face of the at least one polymeric material,
followed by applying of at least a portion of the surrounding
material and curing of the at least a portion of the surrounding
material to laterally embed the at least one waveguide region.
25. A method for fabricating a fiber optic connector including a
ferrule that has a front end, a rear end, and at least one internal
bore extending between the front end and the rear end, the method
comprising: inserting at least one optical fiber through the rear
end of the ferrule into the at least one internal bore; positioning
a terminal end of the at least one optical fiber between the front
end and the rear end; and inserting at least one prefabricated
polymeric material in a front end portion of the at least one
internal bore to cause the at least one prefabricated polymeric
material to extend from a location in front of the terminal end of
the at least one optical fiber to at least the front end of the
ferrule.
26. The method of claim 25, further comprising applying at least
one adhesive material to one or more of the following areas: (a) a
groove in a lateral surface of the at least one prefabricated
polymeric material, (b) at least one cavity in an inner face of the
at least one prefabricated polymeric material, or (c) between the
at least one optical fiber and the at least one internal bore.
27. The method of claim 26, further comprising curing the at least
one adhesive material.
28. The method of claim 25, wherein: the at least one prefabricated
polymeric material comprises a waveguide material having a first
refractive index and a surrounding material having a second
refractive index that differs from the first refractive index; and
the at least one prefabricated polymeric material comprises at
least one waveguide region that extends between the terminal end of
the at least one optical fiber to an outer end face of the at least
one prefabricated polymeric material.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of priority to U.S.
Provisional Application No. 62/508083, filed on May 18, 2017, and
is incorporated herein by reference.
BACKGROUND
[0002] The disclosure relates generally to optical fibers, and more
particularly to fiber optic connectors and methods for fabricating
fiber optic connectors.
[0003] Optical fibers are useful in a wide variety of applications,
including the telecommunications industry for voice, video, and
data transmissions. In a telecommunications system that uses
optical fibers, there are typically many locations where fiber
optic cables that carry the optical fibers connect to equipment or
other fiber optic cables. To conveniently provide these
connections, fiber optic connectors ("connectors" or "optical
connectors") are often provided on the ends of fiber optic cables.
Fiber optic connectors are used to optically connect one optical
fiber to another, or to connect an optical fiber to another device
such as an optical transmitter or an optical receiver.
[0004] A fiber optic connector typically includes a ferrule with
one or more bores that receive one or more optical fibers. The
ferrule supports and positions the optical fiber(s) with respect to
a housing of the fiber optic connector. Thus, when the housing of
the fiber optic connector is mated with another connector (e.g., in
an adapter), the optical fiber in the ferrule is positioned in a
known, fixed location relative to the housing. This allows an
optical connection to be established when the optical fiber is
aligned with another optical fiber in the mating connector.
[0005] In fiber-to-fiber connections, fiber ends are typically
terminated with care to reduce extrinsic coupling loss resulting
from reflection or scattering. An optical fiber end face desirably
should be flat, smooth, and perpendicular or at a desired angle to
a longitudinal axis of the optical fiber. Typical steps in fiber
end preparation include removal of any fiber buffer and coating
materials from an end of the fiber, followed by cleaving the fiber
end, and then followed by polishing. Frequently, a fiber is
inserted and epoxied into a ferrule of a connector assembly with a
fiber portion extending beyond a ferrule end, and then the fiber
end is cleaved (if not cleaved prior to insertion into the ferrule)
and polished with sequentially finer grit polishing media until a
desired fiber flatness and finish are achieved at a position nearly
flush with (e.g., protruding no farther than 50 nm relative to) the
ferrule end. Fiber end preparation requires significant time and
resources, thereby impacting manufacturing efficiency and
increasing production costs.
[0006] When optical fibers of adjacent connectors are mated with
one another, significant mechanical loads may be required to
provide physical contact of adjacent fiber end faces sufficient to
minimize optical signal attenuation. A ceramic ferrule body
exhibits greater stiffness than glass optical fibers, and therefore
acts as a hard stop for compression of an optical fiber in a mated
condition. Typical fiber optic connectors may include optical
fibers protruding forwarding from a ferrule by up to 50 nm, and
faces of adjacent optical fibers may be pressed together with a
maximum force of up to about 11 Newtons. Maintaining such loading
may require mechanical biasing elements (e.g., springs) in fiber
optic connector assemblies to be increased in size and strength.
Additionally, if such loading exerts undue stress on portions of
the optical fibers and/or mechanical biasing elements, then
mechanical reliability of the optical fibers and/or a corresponding
fiber optic connector assembly may be compromised.
SUMMARY
[0007] Aspects of the present disclosure provide fiber optic
connectors with at least one polymeric material that is arranged
within a front end portion of at least one internal bore of a
ferrule at least in front of a terminal end of at least one optical
fiber and extending to an end of the ferrule. Preferably, the at
least one polymeric material is transmissive of desired
wavelengths, is arranged in contact with the terminal end of the at
least one optical fiber, and forms a polymeric end face configured
to transmit optical signals to and/or from the at least one optical
fiber. Methods for fabricating fiber optic connectors are further
provided. The at least one polymeric material may be applied to
(e.g., printed over and/or dispensed into) the front end portion of
the at least one internal bore to contact the at least one optical
fiber. Following such application, the at least one polymeric
material may be cured by any suitable means, such as by one or more
of the following: a chemical, thermal, or photonic interaction
(wherein photonic energy may optionally be supplied by a laser).
Presence of the at least one polymeric material over the terminal
end of the at least one optical fiber may reduce or eliminate the
need for polishing of optical fiber end faces. Additionally,
utilization of polymeric material with a lower modulus of
elasticity than that of glass material of the at least one optical
fiber may enable intimate contact between mating
signal-transmitting surfaces of adjacent connectors to be
maintained without application of high forces and exertion of undue
mechanical stresses on the at least one optical fiber.
[0008] In one embodiment of the disclosure, a fiber optic connector
is provided. The fiber optic connector comprises a ferrule, at
least one optical fiber, and at least one polymeric material. The
ferrule includes a front end, a rear end, and at least one internal
bore extending between the front end and the rear end. The at least
one optical fiber extends through the rear end of the ferrule into
the at least one internal bore. A terminal end of the at least one
optical fiber is positioned between the front end and the rear end
of the ferrule. The at least one polymeric material is arranged
within the at least one internal bore of the ferrule at least in
front of the terminal end of the at least one optical fiber and
extends to at least the front end of the ferrule. For example, the
at least one polymeric material may contact the terminal end of the
at least one optical fiber so as to extend from the terminal end to
at least the front end of the ferrule.
[0009] In another embodiment of the disclosure, a method is
provided for fabricating a fiber optic connector including a
ferrule. The ferrule includes a front end, a rear end, and at least
one internal bore extending between the front end and the rear end.
The method comprises inserting at least one optical fiber through
the rear end of the ferrule into the at least one internal bore,
and positioning a terminal end of the at least one optical fiber
between the front end and the rear end. The method further
comprises applying at least one polymeric material to a front end
portion of the at least one internal bore, to cause the at least
one polymeric material to extend from a location in front of the
terminal end of the at least one optical fiber to at least the
front end of the ferrule. The method further comprises curing the
at least one polymeric material. For example, the at least one
polymeric material may be applied to the terminal end of the at
least one optical fiber so as to contact the terminal end and
extend directly therefrom.
[0010] In another embodiment of the disclosure, another method is
provided for fabricating a fiber optic connector including a
ferrule. The ferrule includes a front end, a rear end, and at least
one internal bore extending between the front end and the rear end.
The method comprises inserting at least one optical fiber through
the rear end of the ferrule into the at least one internal bore,
and positioning a terminal end of the at least one optical fiber
between the front end and the rear end. The method further
comprises inserting at least one prefabricated polymeric material
to a front end portion of the at least one internal bore, to cause
the at least one prefabricated polymeric material to extend from a
location in front of the terminal end of the at least one optical
fiber to at least the front end of the ferrule.
[0011] Additional features and advantages will be set forth in the
detailed description which follows, and in part will be readily
apparent to those skilled in the technical field of optical
connectivity. It is to be understood that the foregoing general
description, the following detailed description, and the
accompanying drawings are merely exemplary and intended to provide
an overview or framework to understand the nature and character of
the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The accompanying drawings are included to provide a further
understanding, and are incorporated in and constitute a part of
this specification. The drawings illustrate one or more
embodiment(s), and together with the description serve to explain
principles and operation of the various embodiments. Features and
attributes associated with any of the embodiments shown or
described may be applied to other embodiments shown, described, or
appreciated based on this disclosure.
[0013] FIG. 1 is a perspective view of an example of a conventional
fiber optic connector incorporating an optical fiber retained in a
bore of a ferrule;
[0014] FIG. 2 is an exploded view of the fiber optic connector of
FIG. 1;
[0015] FIG. 3 is a perspective view of the ferrule of the fiber
optic connector of FIGS. 1 and 2, with the optical fiber received
by the ferrule;
[0016] FIG. 4 is a cross-sectional view of the ferrule and optical
fiber of FIG. 3, with a terminal end of the optical fiber arranged
substantially flush with an end of the ferrule;
[0017] FIG. 5 is a cross-sectional view of a ferrule according to
FIGS. 3 and 4, but with the terminal end of a bare optical fiber
segment retracted rearward between front and rear ends of the
ferrule to define a recess suitable for receiving a polymeric
material;
[0018] FIG. 6 is a magnified cross-sectional view of a portion of
the ferrule and optical fiber of FIG. 5, following addition of a
polymeric material within a front end portion of an internal bore
of the ferrule to contact the terminal end of the optical fiber,
according to one embodiment of the present disclosure;
[0019] FIG. 7 is a magnified cross-sectional view of a portion of a
ferrule having an optical fiber retained in an internal bore
thereof, with a front end portion of the internal bore including a
cylindrical shape having a diameter greater than a medial portion
of the internal bore, and with polymeric material filling the front
end portion of the internal bore to surround a terminal end of the
optical fiber;
[0020] FIG. 8 is a magnified cross-sectional view of the portion of
the ferrule and the optical fiber according to FIG. 7, but modified
with a first (inner) polymeric material filling an inner part of
the front end portion of the internal bore to surround the terminal
end of the optical fiber, and with a second (outer) polymeric
material filling an outer part of the front end portion to overlie
the first polymeric material;
[0021] FIG. 9 is a magnified cross-sectional view of a portion of a
ferrule defining an internal bore, with a medial portion of the
internal bore having a first diameter, and with a front end portion
of the internal bore including a conical shape having an increased
diameter relative to the medial portion and having a maximum
diameter at an end of the ferrule;
[0022] FIG. 10 is a magnified cross-sectional view of the ferrule
portion of FIG. 9, following insertion of an optical fiber through
the medial portion of the internal bore into the front end portion
thereof with a terminal end of the optical fiber distanced from the
front end of the ferrule, and following addition of a polymeric
material into the front end portion of the internal bore to
surround the terminal end of the optical fiber;
[0023] FIG. 11 is a cross-sectional view of two optical
fiber-retaining ferrules with polymeric material arranged in
conical end portions of internal bores thereof according to FIG.
10, with the ferrule ends and respective polymeric materials
registered with and contacting one another to permit optical signal
transmission between the optical fibers;
[0024] FIG. 12 is a magnified cross-sectional view of a central
portion of FIG. 11;
[0025] FIG. 13 is a further magnified cross-sectional view of a
central portion of FIG. 12;
[0026] FIG. 14 is a perspective view of a front end portion of a
ferrule containing a multi-core optical fiber, with a polymeric
material arranged between terminal ends of the optical fibers and
an end of the ferrule;
[0027] FIG. 15 is a magnified perspective view of the front end
portion and polymeric material of FIG. 14, showing outwardly
protruding dome-shaped compression bumps each configured to be
registered with an individual fiber of a multi-core optical
fiber;
[0028] FIG. 16 is a cross-sectional view of the polymeric material
of FIG. 15 abutting a terminal end of a multi-core optical fiber
within an internal bore of the ferrule, with individual cores of
the multi-core optical fiber being registered with different
dome-shaped compression bumps of the polymeric material;
[0029] FIG. 17 is a cross-sectional view of a polymeric material
assembly suitable for fabrication in an internal bore of a ferrule
and arranged to abut a terminal end of a multi-core optical fiber,
with the polymeric material assembly including waveguide material
shaped into multiple waveguide regions and including surrounding
material arranged to laterally embed the waveguide regions;
[0030] FIG. 18 is a cross-sectional view of the polymeric material
assembly of FIG. 17 abutting the terminal end of the multi-core
optical fiber in the internal bore of the ferrule, with the
waveguide regions extending between an outer face of the polymeric
material assembly and terminal ends of different optical fiber
cores;
[0031] FIG. 19 is a cross-sectional view of end portions of two
ferrules according to FIG. 18 arranged to be mated with one
another, with waveguide regions of a polymeric material assembly of
the first ferrule abutting and being registered with waveguide
regions of a polymeric material assembly of the second ferrule, and
being configured to transmit optical signals from individual
optical fiber cores of a first multi-core optical fiber to
individual fiber cores of a second multi-core optical fiber;
[0032] FIG. 20 is a cross-sectional view of a prefabricated
polymeric material assembly suitable for insertion in an internal
bore of a ferrule and arranged to abut a terminal end of a
multi-core optical fiber, with the prefabricated polymeric material
assembly including waveguide material shaped into multiple
waveguide regions and including surrounding material arranged to
laterally embed the waveguide regions and define a groove to
receive adhesive material for attachment of the prefabricated
polymeric material assembly within the internal bore of the
ferrule;
[0033] FIG. 21 is a cross-sectional view of the prefabricated
polymeric material assembly of FIG. 20 abutting the terminal end of
the multi-core optical fiber in the internal bore of the ferrule,
with the waveguide regions extending between an outer face of the
prefabricated polymeric material assembly and terminal ends of
different optical fiber cores of the multi-core optical fiber, and
with the adhesive material positioned in the groove;
[0034] FIG. 22 is a cross-sectional view of another embodiment of a
prefabricated polymeric material assembly suitable for insertion in
an internal bore of a ferrule and arranged to abut a terminal end
of a multi-core optical fiber, with the prefabricated polymeric
material assembly including waveguide material shaped into multiple
waveguide regions and including surrounding material arranged to
laterally embed the waveguide regions and define a groove and a
plurality of cavities configured to receive adhesive material for
attachment of the prefabricated polymeric material assembly within
the internal bore of the ferrule;
[0035] FIG. 23 is a cross-sectional view of the prefabricated
polymeric material assembly of FIG. 22 abutting the terminal end of
the multi-core optical fiber in the internal bore of the ferrule,
with the waveguide regions extending from an outer face of the
prefabricated polymeric material assembly, and with the adhesive
material positioned in the groove and the plurality of cavities
arranged between the waveguide regions and terminal ends of optical
fiber cores of the multi-core optical fiber;
[0036] FIG. 24 is a perspective view of a fiber optic connector and
an associated fiber optic cable forming a fiber optic cable
assembly, with the fiber optic connector including a multi-fiber
ferrule with a single ferrule boot;
[0037] FIG. 25 is an exploded perspective view of the fiber optic
cable assembly of FIG. 24; and
[0038] FIG. 26 is a cross-sectional view of a multi-fiber ferrule
with polymeric material protrusions of different lengths.
DETAILED DESCRIPTION
[0039] Various embodiments will be further clarified by examples in
the description below. As will be discussed in more detail below,
the description generally relates to a fiber optic connector
including at least one polymeric material that is arranged within a
front end portion of at least one internal bore of a ferrule, and
that extends from a terminal end of at least one optical fiber to
an end of the ferrule. At least a portion of the at least one
polymeric material is arranged in an optical path of signals borne
by the at least one optical fiber; accordingly, the at least one
polymeric material is transmissive of desired wavelengths. The at
least one polymeric material is arranged in contact with the
terminal end of the at least one optical fiber and forms a
polymeric end face, with the at least one polymeric material
serving as a conduit for transmitting optical signals to and/or
from the at least one optical fiber. Methods for fabricating fiber
optic connectors are further provided, in which the at least one
polymeric material may be applied to the front end portion of the
at least one internal bore to contact the at least one optical
fiber, and the at least one polymeric material may be cured
thereafter.
[0040] Before discussing fiber optic connector embodiments and
fabrication methods utilizing polymeric material arranged between a
terminal end of at least one optical fiber and an end of a ferrule,
a brief overview of a connector 10 shown in FIGS. 1 and 2, as well
as a ferrule 12 shown in FIGS. 3 and 4, will be provided to
facilitate discussion. It is to be appreciated that the ferrules
and polymeric material portions shown in subsequent figures may be
used with the same type of connector as the connector 10. Although
the connector 10 is shown in the form of a SC-type connector,
persons skilled in the field of optical connectivity will
appreciate that the connector 10 is merely an example, and that the
general principles disclosed with respect to the ferrules and other
components shown in subsequent figures may also be applicable to
other connector and/or ferrule designs. For example, in certain
embodiments, a connector may include a ferrule configured to
receive multiple optical fibers and/or at least one multi-core
optical fiber in one or more internal bores of the ferrule.
[0041] As shown in FIGS. 1 and 2, the connector 10 includes the
ferrule 12, a ferrule holder 14 from which the ferrule 12 extends,
a housing 16 having a cavity 30 in which the ferrule holder 14 is
received, and a connector body 18 configured to retain the ferrule
holder 14 within the housing 16. The connector body 18 may also be
referred to as "retention body 18" or "crimp body 18". One portion
of the connector body 18 is received in the housing 16. The ferrule
12 includes a small diameter bore section 20 (or "micro-hole")
configured to support an optical fiber 22, which is secured in the
small diameter bore section 20 using an adhesive material (e.g.,
epoxy). The ferrule holder 14 includes a ferrule holder bore 24
from which the ferrule 12 extends. More specifically, a rear
portion 26 of the ferrule 12 is received in the ferrule holder bore
24 defined in (at least) a first portion 28 of the ferrule holder
14, and is secured therein in a known manner (e.g., press-fit,
adhesive, molding the ferrule holder 14 over the rear portion 26 of
the ferrule 12, etc.). The ferrule 12 and ferrule holder 14 may
even be a monolithic structure in some embodiments. The ferrule
holder 14 is biased to a forward position within the cavity 30 of
the housing 16 by a spring 32, which extends over a second portion
34 of the ferrule holder 14 that has a reduced cross-sectional
diameter/width compared to the first portion 28.
[0042] FIGS. 1 and 2 illustrate a rear portion of the housing 16
having cut-outs or slots 36 on opposite surfaces so as to define a
split shroud. The connector body 18 is generally tubular in shape
with a medial shoulder 38 arranged between different diameter
portions. The connector body 18 further includes protrusions 40
(which may embody tabs) configured to be snapped into the slots 36
of the housing 16 and retained therein due to the geometries of the
components and the presence of locking tabs 42 proximate to a
leading edge of each slot 36 of the housing 16.
[0043] When the connector 10 is assembled as shown in FIG. 1, a
front end 44 of the ferrule 12 projects beyond a front end 46 of
the housing 16. The front end 44 of the ferrule 12 presents the
optical fiber 22 retained therein for optical coupling with a
mating component (e.g., another fiber optic connector; not shown),
with the ferrule 12 serving to generally align the optical fiber 22
in an axial direction along a longitudinal axis 48. The housing 16
includes a roughly rectangular cross-sectional shape perpendicular
to the longitudinal axis 48, with two adjacent non-beveled corners
50 and two adjacent beveled corners 52 embodying transitions
between four outer faces of the housing 16 proximate to the front
end 46 of the housing 16. The non-beveled corners 50 and the
beveled corners 52 in combination ensure that the connector 10 must
be in a specific orientation when received by a connector receiving
structure (e.g., a female connector, a socket, a receptacle, etc.
(not shown)).
[0044] FIGS. 3 and 4 provide perspective and cross-sectional views,
respectively, of the ferrule 12 that was previously shown in FIGS.
1 and 2 as part of the connector 10. The ferrule 12 is generally
cylindrical in shape, and defines a bore 19 extending between front
and rear ends 44, 54. Exemplary materials for fabrication of the
ferrule 12 include ceramic or glass. In FIG. 4, the bore 19
comprises the small diameter bore section 20, a larger diameter
bore rear section 56, and an intermediate bore section 58. The
intermediate bore section 58 has a tapered diameter and extends
between the small diameter bore section 20 and the larger diameter
bore rear section 56. As shown in FIG. 4, the larger diameter bore
rear section 56 is proximate to the rear end 54 of the ferrule 12
(e.g., the larger diameter bore rear section 56 extends inward from
the rear end 54), and the small diameter bore section 20 extends
from the intermediate bore section 58 to the front end 44 of the
ferrule 12. A segment of coated optical fiber 22 is received by the
larger diameter bore rear section 56, and transitions to a segment
of bare optical fiber 60 that has a small diameter than the segment
of coated optical fiber 22 and that is received by the small
diameter bore section 20. An adhesive material, such as epoxy (not
shown), may be provided between the segment of bare optical fiber
60 and the small diameter bore section 20 to secure the segment of
bare optical fiber 60 to the ferrule 12. With continued reference
to FIG. 4, the segment of bare optical fiber 60 extends to the
front end 44 of the ferrule 12, and includes a terminal end 62 that
is substantially flush with the front end 44. This terminal end 62
is typically polished to attain a desired fiber flatness and finish
suitable for mating with a suitably prepared fiber of a mating
connector or receptacle (not shown).
[0045] Now that general overviews of the connector 10 and the
ferrule 12 have been provided, embodiments of the present
disclosure will be described.
[0046] FIG. 5 is a cross-sectional view of an example of a ferrule
12 according to FIG. 4, but with the terminal end 62 of the bare
optical fiber 60 retracted rearward within the small diameter bore
section 20 to a position between the front end 44 and the rear end
54 of the ferrule 12. As was the case with FIG. 4, the ferrule 12
includes an internal bore consisting of the small diameter bore
section 20, the larger diameter bore rear section 56, and the
intermediate bore section 58. Positioning of the terminal end 62 of
the bare optical fiber 60 between the front and rear ends 44, 54
yields a recess 70 (i.e., an unfilled portion of the small diameter
bore section 20) proximate to the front end 44 of the ferrule 12.
The ferrule 12 and the internal bore may each be considered to
include a rear portion 64 (of a first average diameter), a medial
portion 66 (of a second average diameter), and a front end portion
68 (of a third average diameter). In certain embodiments, the third
average diameter of the front end portion 68 exceeds the second
average diameter of the medial portion 66. The rear portion 64
encompasses the larger diameter bore rear section 56 and the
intermediate bore section 58. The larger diameter bore rear section
56 receives a segment of coated optical fiber 22. The medial
portion 66 encompasses the small diameter bore section 20 that
extends between the intermediate bore section 58 and the terminal
end 62 of the bare optical fiber 60. The front end portion 68
encompasses the small diameter bore section 20 that extends between
the terminal end 62 of the bare optical fiber 60 and the front end
44 of the ferrule 12. In the case of FIG. 5, the front end portion
68 of the internal bore is coextensive with the recess 70. Such
recess 70 is suitable for receiving and retaining at least one
polymeric material, as discussed in connection with FIG. 6.
[0047] FIG. 6 is a magnified cross-sectional view of a portion of
the ferrule 12 and bare optical fiber 60 of FIG. 5, following
addition of a polymeric material 72 within the front end portion 68
of the internal bore of the ferrule 12 (i.e., with such polymeric
material 72 filling the recess 70 shown in FIG. 5). The polymeric
material 72 within the front end portion 68 extends forward from
the terminal end 62 of the bare optical fiber 60 to at least the
front end 44 of the ferrule 12. In certain embodiments, the
polymeric material 72 extends forward slightly beyond the front end
44 of the ferrule 12. The front end portion 68 of the internal bore
includes the same dimensions as the small diameter bore section 20,
which embodies a medial portion 66 of the internal bore. Due to a
close dimensional fit between the bare optical fiber 60 and the
small diameter bore section 20, as well as the potential presence
of adhesive material (not shown) therebetween, substantially an
entirety (e.g., at least 90%) of the polymeric material 72 may be
arranged forward of the terminal end 62 of the bare optical fiber
60 (i.e., without presence of significant polymeric material 72 in
contact with a side wall of the bare optical fiber 60).
[0048] To promote intimate physical contact between the polymeric
material 72 and the terminal end 62 of the bare optical fiber 60
without gaps, in certain embodiments the polymeric material 72 is
supplied to the front end portion 68 of the internal bore in a
flowable form (e.g., a liquid, gel, suspension, or the like), and
thereafter is cured to cause the polymeric material 72 to stiffen
or at least partially solidify. Various techniques for curing
polymeric material may be used, such as one or more of photonic,
thermal, or chemical interaction. In certain embodiments, the
polymeric material 72 may be supplied to the front end portion 68
of the internal bore by three-dimensional printing. In certain
embodiments, the polymeric material 72 may be at least partially
cured by impingement thereon of emissions (e.g., in an ultraviolet
(UV) or near-UV wavelength range) of a laser, a light-emitting
diode, or another suitable electromagnetic radiation source.
Preferably, the polymeric material 72 may be processed to achieve
more precise dimensioning, more precise mating locations, and/or
greater uniformity of an end face than may be obtained using glass
polishing processes traditionally utilized with optical fibers. In
this regard, optical fibers and/or optical fiber cores overlaid
with one or more polymeric materials as disclosed herein may yield
end faces and end conditions that are substantially identical in
nanometer scale, thereby providing improved uniformity relative to
use of traditional optical fiber polishing processes. In certain
embodiments, a micromold providing a negative representation of one
more raised and/or recessed features may be arranged over a front
end portion of an internal bore (e.g., during and/or after
application of flowable polymeric material), and such polymeric
material may be partially or fully cured with the micromold in
place, followed by release of the micromold to define one or more
raised and/or recessed features in and/or on the polymeric
material. To reduce or minimize the possibility of trapping air
bubbles in the polymeric material as disclosed herein, in certain
embodiments, polymeric material may be applied and/or cured in a
sub-atmospheric pressure environment.
[0049] Examples of desirable polymeric material that may be used
include, but are not limited to, UV-curable inorganic-organic
hybrid polymers. Such materials exhibit both inorganic and organic
units. The organic units bear polymerizable moieties and various
functional groups that enable photo-induced curing, whereas an
inorganic backbone provides good optical transparency as well as
high thermal, chemical, and mechanical stability. One type of
hybrid polymer includes ORMOCER.RTM. (a trademark of Fraunhofer
Gesellschaft zur Forderung der angewandten Forschung e.V., Munich,
Germany) polymers, which are used in multiple commercial
applications. The synthesis of ORMOCER.RTM.-type inorganic-organic
hybrid polymers is based on a sol-gel reaction, in which a
hydrolysis-condensation reaction of organically modified silicic
acid precursors (i.e., silicon-containing monomers) leads to
nano-scaled oligomers with inorganic backbones. Addition of various
functional additives and photo-initiators creates a solvent-free
viscous oligomer solution that can be cross-linked upon exposure to
UV light. Hybrid polymers based on similar chemistries that may be
used include OrmoComp.TM. and OrmoClear.TM. polymers commercially
available from Micro Resist Technology GmbH (Berlin, Germany).
[0050] FIGS. 5 and 6 depict features useful for describing steps of
a method for fabricating a fiber optic connector utilizing the
ferrule 12. An advance method step may include preparing the coated
optical fiber 22 for connectorization by stripping external layers
away from a front segment to yield a segment of bare optical fiber
60. Another advance method step may include supplying an adhesive
material to the small diameter bore section 20 of the ferrule 12.
Thereafter, a method step may include inserting the segment of bare
optical fiber 60 through the rear end 54 of the ferrule 12, through
the larger diameter bore rear section 56, and through the small
diameter bore section 20 to cause a leading end of the bare optical
fiber 60 to extend beyond the front end 44 of the ferrule 12. Such
step may cause excess adhesive material previously supplied to the
internal bore of the ferrule 12 to propagate to (e.g., be carried
by) a leading end of the bare optical fiber 60. Such leading end
may then be processed (e.g., by cleaving and application of one or
more cleaning steps) to remove any excess adhesive material and
yield the terminal end 62 of the bare optical fiber 60. Thereafter,
the terminal end 62 may be retracted into the internal bore of the
ferrule 12 to a position between the front and rear ends 44, 54
thereof, with such retraction desirably serving to create the
recess 70 shown in FIG. 5. Then, as shown in FIG. 6, at least one
polymeric material 72 is applied to the front end portion 68 of the
internal bore, and such polymeric material 72 is cured, causing the
polymeric material 72 to extend from the terminal end 62 of the
bare optical fiber 60 to at least the front end 44 of the ferrule
12, and preferably slightly forward of the front end 44.
Alternatively, the polymeric material 72 may be prefabricated
(shown in FIGS. 20-23) and inserted into the internal bore of the
ferrule 12. Adhesive (e.g., epoxy or the like) may be applied
before or after insertion of the prefabricated polymeric material
72. Thereafter, the adhesive may be cured to affix the
prefabricated polymeric material 72 within the internal bore of the
ferrule 12.
[0051] Presence of polymeric material between optical fiber end
faces of two mating connector assemblies necessarily distances the
optical fiber end faces from one another. Generally, increasing
thickness of this polymeric material tends to reduce the mechanical
loads required to enable intimate contact between mating
signal-transmitting surfaces of adjacent connectors, but also tends
to increase insertion losses and attenuation of optical signals.
Restated, the thicker the polymeric material overlying terminal
ends of optical fibers, the more robust the mechanical interface
will be between mating signal-transmitting surfaces of adjacent
connectors, but optical performance will suffer. Through
appropriate modeling, Applicant has determined that if
OrmoStamp.TM. hybrid polymer material or OrmoClear.TM. hybrid
polymer material (both commercially available from Micro Resist
Technology GmbH (Berlin, Germany)) is used as a polymeric material
between a terminal end of an optical fiber and an end face, then an
acceptably low insertion loss value of no greater than 0.5 dB may
be obtained over a distance of no greater than about 50 .mu.m for
physical contact between two connectors. Since this distance
threshold corresponds to passage of signals through two mated
polymeric materials, each polymeric material should have a
thickness of no greater than about 25 .mu.m overlying a terminal
end of a corresponding optical fiber to maintain a desirably low
insertion loss of no greater than 0.5 dB according to this example.
Thus, in certain embodiments, polymeric material regions overlying
terminal ends of optical fibers may have thicknesses in a range of
from about 0.5 .mu.m to about 25 .mu.m. If greater insertion losses
may be tolerated, then the foregoing maximum thickness values for
polymeric materials may be increased (e.g., to about 50 .mu.m), and
vice-versa. In certain embodiments utilizing waveguiding regions
within polymeric material assemblies, the foregoing thickness
values may be increased, as discussed in more detail
hereinafter.
[0052] To facilitate greater mechanical compression of polymeric
material proximate to a terminal end of an optical fiber, in
certain embodiments the polymeric material may extend rearward past
the terminal end (e.g., with the polymeric material forming an
annular cross-sectional shape) and laterally encapsulate the
optical fiber. Such arrangement may permit the thickness of
polymeric material overlying a terminal end of an optical fiber to
be decreased, thereby permitting the optical distance between two
optical fibers of a connection to be decreased and enhancing
optical performance. Intimate physical contact between polymeric
end faces is desirable to avoid a gap that would attenuate
transmission of optical signals.
[0053] To permit polymeric material to laterally encapsulate an
optical fiber, in certain embodiments, a front end portion of an
internal bore of a ferrule may include a greater diameter than a
medial portion of the internal bore. An increased diameter front
end portion of an internal bore of a ferrule may be provided in
various shapes, including (but not limited to) cylindrical shapes
as shown in FIGS. 7 and 8, and conical (or frustoconical) shapes as
shown in FIGS. 9 and 10.
[0054] FIG. 7 is a magnified cross-sectional view of a portion of a
ferrule 82 retaining a segment of a bare optical fiber 60. The
ferrule 82 includes an internal bore 19 encompassing a small
diameter bore section 20 and a cylindrically shaped larger diameter
bore section 92 that is proximate to a front end 44 of the ferrule
82. The ferrule 82 and the internal bore 19 may each be considered
to include a medial portion 86 and a front end portion 88, with the
medial portion 86 of the internal bore 19 encompassing the small
diameter bore section 20 and the front end portion 88 encompassing
the larger diameter bore section 92. The segment of bare optical
fiber 60 extends forward from the small diameter bore section 20
into the larger diameter bore section 92, but a terminal end 62 of
the bare optical fiber 60 does not extend to the front end 44 of
the ferrule 82. A polymeric material 94 is arranged within the
larger diameter bore section 92 (embodying the front end portion 88
of the internal bore 19) to overlap the terminal end 62 of the bare
optical fiber 60 and encapsulate lateral portions thereof. The
polymeric material 94 further defines a polymeric end face 96 that
preferably protrudes slightly forward beyond the front end 44 of
the ferrule 82. Presence of a portion of the polymeric material 94
extending rearward past the terminal end 62 of the bare optical
fiber 60 may enhance mechanical compliance or the cushioning effect
of the polymeric material 94 without requiring an undue thickness
of polymeric material 94 to be placed between the terminal end 62
of the bare optical fiber 60 and the polymeric end face 96. Forward
protrusion of the polymeric end face 96 slightly beyond the front
end 44 permits the polymeric material 94 to intimately contact a
signal-transmitting surface of an adjacent connector (e.g., an end
face comprising the same or a similar polymeric material, or
comprising a suitably polished glass tip of an optical fiber, not
shown).
[0055] In certain embodiments, multiple polymeric materials may be
arranged within (and optionally extend beyond) a front end portion
of at least one internal bore of a ferrule, with at least some
polymeric materials sequentially arranged in an optical path of
signals borne by at least one optical fiber. For instance,
different polymeric materials may be deposited as sequential
layers, with different layers embodying different properties and/or
serving different functions, such as: scratch resistance,
anti-reflectance, anti-static, and/or lensing utility (e.g., beam
shaping). In certain embodiments, different polymeric materials may
be provided by altering the presence and/or concentration of
different additives. Enhancement of scratch resistance may
beneficially enable a higher number of connector mating cycles,
provide robustness against dirt and contamination, and enable end
faces to undergo various cleaning procedures with reduced impact on
reliability. Enhancement of anti-reflectance properties may enable
a reduction in insertion loss and further stabilize optical
performance in the use of mated fiber optic connectors. Enhancement
of anti-static properties may provide a self-cleaning effect,
thereby reducing the frequency and/or amount of cleaning required,
or simply avoiding contamination altogether. Provision of lensing
utility with one or more optical material layers may permit a beam
carried by an optical fiber to be better guided in a connection
location, to avoid undue signal transmission losses.
[0056] FIG. 8 illustrates the ferrule 82 and the bare optical fiber
60 shown in FIG. 7, but with modification to materials arranged
proximate to the terminal end 62 of the bare optical fiber 60. As
shown in FIG. 8, the segment of bare optical fiber 60 still extends
forward from the small diameter bore section 20 into the larger
diameter bore section 92. Additionally, the polymeric material 94
is arranged within a part of the larger diameter bore section 92
(embodying the front end portion 88 of the internal bore 19) to
overlap the terminal end 62 of the bare optical fiber 60 and
encapsulate lateral portions of the bare optical fiber 60 in the
larger diameter bore section 92. The polymeric material 94 in this
embodiment, however, does not define an end face for contacting a
signal-transmitting surface of another connector. Instead, the
polymeric material 94 embodies a first polymeric material, and a
second polymeric material 98 is sequentially arranged over (i.e.,
forward of) the first polymeric material 94, with the second
polymeric material 98 forming a polymeric end face 100 configured
to permit transmission of optical signals to and/or from the bare
optical fiber 60. Optionally, the polymeric end face 100 may extend
slightly forward of the front end 44 of the ferrule 82. As shown,
layers of both the second polymeric material 98 and a portion of
the first polymeric material 94 are arranged in an optical path of
signals borne by the bare optical fiber 60. Although only two
layers of the polymeric materials 94, 98 are shown, it is to be
appreciated that any suitable number of two, three, four, or five
or more layers of polymeric material may be sequentially arranged
in (or forward of) the front end portion 88 of the internal bore 19
of the ferrule 82. In certain embodiments, one or more initial
polymeric material layers may be applied and cured, followed by
application and curing of one or more subsequent polymeric material
layers. In other embodiments, one or more initial polymeric
material layers may be applied, one or more subsequent polymeric
material layers may be applied, and the foregoing layers may be
cured in a substantially simultaneous manner (e.g., utilizing one
or more curing operations).
[0057] In contrast to the cylindrically shaped larger diameter bore
section 92 of the front end portion 88 of the internal bore 19
shown in FIGS. 7 and 8, in certain embodiments, ferrules may
include internal bores having conical or frustoconical front end
portions. FIG. 9 is a magnified cross-sectional view of a portion
of a ferrule 102 defining an internal bore 19 encompassing a small
diameter bore section 20 and a larger diameter bore section 112.
The ferrule 102 and the internal bore 19 may each be considered to
include a medial portion 106, and a front end portion 108, with the
medial portion 106 of the internal bore 19 encompassing the small
diameter bore section 20, and the front end portion 108
encompassing the larger diameter bore section 112. The front end
portion 108 of the internal bore 19 includes a generally conical
shape having an increased diameter relative to the medial portion
106 of the internal bore 19, and having a maximum diameter at a
front end 44 of the ferrule 102. The front end portion 108 of the
internal bore 19 is suitable for receiving at least one polymeric
material, as will be described in greater detail in connection with
FIG. 10.
[0058] FIG. 10 is a magnified cross-sectional view of the ferrule
102 of FIG. 9, following insertion of a bare optical fiber 60
through the medial portion 106 of the internal bore 19 into the
front end portion 108 thereof. The medial portion 106 of the
internal bore 19 corresponds to a small diameter bore section 20.
As shown, a terminal end 62 of the bare optical fiber 60 is
distanced rearward from the front end 44 of the ferrule 102. The
front end portion 108 of the internal bore 19 (corresponding to the
larger diameter bore section 112) contains a polymeric material 114
that covers the terminal end 62 of the bare optical fiber 60 and
also laterally encapsulates the portion of the bare optical fiber
60 contained within the front end portion 108 of the internal bore
19. The polymeric material 114 defines a polymeric end face that
encompasses a central portion 116 and a peripheral portion 118. At
least a portion of the polymeric end face (e.g., including at least
the central portion 116) may extend forward beyond the front end 44
of the ferrule 102, with a maximum forward extension of the
polymeric material 114 corresponding to a forward projection of the
terminal end 62 of the bare optical fiber 60. Such arrangement
enables compression of the polymeric material 114, particularly
when mated with a correspondingly shaped second polymeric end face,
to reduce or eliminate a boundary between mated end faces. As shown
in FIG. 10, the polymeric material 114 has a maximum diameter
(i.e., at the polymeric end face) that exceeds a diameter of the
bare optical fiber 60, such that a portion of the polymeric
material 114 (i.e., forming a generally annular shape) extends
laterally relative to a forward projection of the terminal end 62
of the bare optical fiber 60. In certain embodiments, a central
volume of the polymeric material 114 (e.g., between the central
portion 116 of the polymeric end face and the terminal end 62 of
the bare optical fiber 60) and a peripheral volume of the polymeric
material 114 may be subject to different curing and/or shaping
steps to separately affect their mechanical and/or optical
properties. For example, one or more laser beams may be focused on
a central volume of the polymeric material 114 according to a first
time and/or energy profile as part of a first curing operation, and
one or more laser beams may be focused on a peripheral volume of
the polymeric material 114 according to a second time and/or energy
profile as part of a second curing operation. Alternatively, the
central and peripheral volumes of the polymeric material 114 may be
subject to the same curing and/or shaping steps, whether performed
simultaneously or at different times. In certain embodiments, the
peripheral portion 118 of the end face of the polymeric material
114 may protrude less forwardly than the central portion 116
thereof, such that the central portion 116 may form a small contact
area compression bump. Such a compression bump (also referred to as
a protrusion) may embody a smaller diameter domed, hemispheric,
cylindrical, or similar shape extending forward relative to the
peripheral portion 118, wherein the polymeric end face may be
perpendicular to, or slightly angled (e.g., 1-15 degree angle, 8
degree angle, etc.) from perpendicular, relative to a longitudinal
axis of at least one fiber or fiber core , as the case may be for
single mode connectors. Further, the compression bump may decrease
the amount of compressive force required to achieve a desired
contact pressure between mating end faces of connectors utilizing
this feature.
[0059] In certain embodiments, the ferrule 102 may be backward
compatible with ferrules incorporating fibers having polished end
faces, such as the ferrule 12 of FIGS. 3 and 4. In particular, as
noted above, the ferrule 12 of FIGS. 3 and 4 includes ceramic or
glass which acts as a hard stop. The compression bump of the
polymeric material 114 is deformable upon contact with the ferrule
12 of FIGS. 3 and 4, thereby closing gaps in the optical
connection. The ferrule 102, and in particular, the compression
bump of the polymeric material 114, is designed and configured to
protect the polymeric material 114 from being overstressed upon
engagement with the ferrule 12 of FIGS. 3 and 4. It is also noted
that other ferrules described herein may also be backwards
compatible.
[0060] FIG. 11 is a cross-sectional view of two optical
fiber-retaining ferrules 102A, 102B each embodying the features of
the portion of a ferrule 102 shown in FIG. 10. Additionally, FIG.
12 is a magnified cross-sectional view of a central portion of FIG.
11, and FIG. 13 is an even further magnified cross-sectional view
of a central portion of FIG. 12. Different magnifications are
provided in FIGS. 11-13 to enable specific features to be
emphasized where necessary. Referring generally to FIGS. 11-13,
each ferrule 102A, 102B includes a front end 44A, 44B, a rear end
54A, 54B, and polymeric material 114A, 114B arranged in a conical
shape within a front end portion 108A, 108B of an internal bore.
Each internal bore encompasses a small diameter bore section 20A,
20B arranged between a larger diameter bore section 112A, 112B and
a larger diameter rear bore section 56A, 56B. At least central
portions 116A, 116B of the end faces of the polymeric materials
114A, 114B are arranged in contact with one another to permit
optical signal transmission between segments of bare optical fibers
60A, 60B retained in the small diameter bore sections 20A, 20B of
the respective ferrules 102A, 102B. The ferrules 102A, 102B and
corresponding internal bores may each be considered to include a
rear portion 104A, 104B, a medial portion 106A, 106B, and the
corresponding front end portion 108A, 108B. Each rear portion 104A,
104B encompasses a larger diameter bore rear section 56A, 56B that
receives a segment of coated optical fiber 22A, 22B. Each medial
portion 106A, 106B encompasses the small diameter bore section 20A,
20B, and each front end portion 108A, 108B encompasses the larger
diameter bore section 112A, 112B that contains polymeric material
114A, 114B as well as a terminal end 62A, 62B of the corresponding
bare optical fibers 60A, 60B. As shown in FIGS. 12 and 13, the
terminal end 62A, 62B of each bare optical fiber 60A, 60B is
arranged rearward of a front end 44A, 44B of the corresponding
ferrule 102A, 102B. As shown in FIG. 13, each polymeric material
114A, 114B includes a polymeric end face including a central
portion 116A, 116B (which is arranged forward of the terminal end
62A, 62B of the corresponding bare optical fiber 60A, 60B) and a
peripheral portion 118A, 118B. A peripheral portion 118A, 118B of
each polymeric material 114A, 114B laterally encapsulates a portion
of the corresponding bare optical fiber 60A, 60B. As shown in FIGS.
12 and 13, at least a central portion 116A, 116B of the polymeric
end face of each polymeric material 114A, 114B extends slightly
forward of the front end 44A, 44B of the corresponding ferrule
102A, 102B, such that less than the entirety of each ferrule front
end 44A, 44B contacts the other.
[0061] Separately from adjustment of the diameter of a front end
portion of an internal bore of a ferrule in which polymeric
material may be deposited, properties such as size, shape, and
modulus of elasticity of one or more forwardly-projecting portions
of a polymeric end face may be selected to achieve a desired
interfacial contact pressure for a given application of force.
Glass has a modulus of elasticity of about 70,000 MPa. If polymeric
material having a lower modulus of elasticity than that of glass is
used, then the force required to create physical contact through an
optical interface may be reduced. Conversely, if polymeric material
having a higher modulus of elasticity than glass is used, then at
least some compressive mechanical load will be applied to a glass
fiber retained therein upon creation of a physical contact
condition with another mating end surface. In certain embodiments,
one or more polymeric materials arranged in an internal bore of a
ferrule proximate to a terminal end of an optical fiber comprises a
modulus of elasticity that is in a range of about 20% to about 90%,
or a range of about 25% to about 75%, or a range of about 30% to
about 65%, or a range of about 35% to about 60% of a modulus of
elasticity of glass material of the optical fiber. In certain
embodiments, the one or more polymeric materials comprise a modulus
of elasticity no greater than about 90%, about 80%, about 70%,
about 60%, about 50%, or about 40% of a modulus of elasticity of
the glass material of the optical fiber.
[0062] Since pressure may be calculated as force divided by area, a
reduction in contact area tends to increase the amount of applied
pressure for a given force, and vice-versa. Similarly, if it is
desired to reduce the amount of force required to obtain a specific
contact pressure, then reducing the contact area along a front
surface of a polymeric end face may be a desirable alternative. Use
of precise material deposition and/or curing process steps as
disclosed herein (e.g., 3D printing, focused laser curing,
micromold assisted curing, etc.) may provide a basis for tailoring
surface shapes and/or surface features of polymeric end faces
configured to provide physical contact through an optical
interface, to enable transmission of optical signals to and/or from
at least one optical fiber of a fiber optic connector disclosed
herein.
[0063] Certain embodiments of the present disclosure include
surface shapes and/or surface features of polymeric end faces
configured to create a physical contact condition with another
mating surface to permit transmission of optical signals to and/or
from optical fibers to accommodate the use of multi-core optical
fibers with fiber optic connectors as disclosed herein. One such
embodiment is disclosed in connection with FIGS. 14-16.
[0064] FIG. 14 is a perspective view of a front portion of a
ferrule 12 that contains a multi-core optical fiber (not shown),
with a polymeric material (shown in more detail in FIG. 15)
arranged between a terminal end of the multi-core optical fiber and
a front end 44 of the ferrule 12. The polymeric material includes a
front end face 122 and also defines features extending beyond the
front end 44 of the ferrule 12. FIG. 15 is a magnified perspective
view of the polymeric material 120 that defines the front end face
122 shown in FIG. 14. As shown in FIG. 15, the front end face 122
of the polymeric material 120 includes four compression bumps
124A-124D (also known as compression spots) that are dome-shaped
(convex) and protrude forward relative to the front end face 122.
The polymeric material 120 further includes a lateral (cylindrical)
boundary 126 that may be arranged to contact the end portion of an
internal bore of a ferrule (e.g., ferrule 12 shown in FIG. 14). The
polymeric material 120 further includes a rear face 128 suitable
for contacting a terminal end of a bare optical fiber (not shown).
Each dome-shaped compression bump 124A-124D is configured to be
registered (e.g., aligned along a central axis) with an individual
core of a multi-core optical fiber. Although the polymeric material
120 of FIG. 15 is illustrated in a stand-alone state, it is to be
appreciated that in preferred embodiments, the polymeric material
120 may be fabricated in an end portion of a ferrule (e.g., by
applying polymeric material in a flowable form to an end portion of
an internal bore containing an optical fiber, followed by curing,
or by any other methods disclosed herein).
[0065] FIG. 16 is a cross-sectional view of the polymeric material
120 of FIG. 15 arranged within an internal bore 144 of a ferrule
142. The lateral boundary 126 of the polymeric material 120 is
arranged in contact with the internal bore 144 of the ferrule 142,
and the rear face 128 of the polymeric material 120 is arranged in
contact with a terminal end 132 of a multi-core optical fiber 130
retained by the ferrule 142. The multi-core optical fiber 130
includes fiber cores 134A-134D that are distributed within a
surrounding glass material 136. As shown, individual fiber cores
134A, 134D of the multi-core optical fiber 130 are registered with
different dome-shaped compression bumps 124A, 124D of the polymeric
material 120. Relative to a hypothetical device with a flat end
face lacking the compression bumps 124A-124D, presence of the
compression bumps 124A-124D extending forward from the front face
122 enables a smaller force to be applied to achieve a desired
interface pressure between contacting polymeric end faces of mating
connectors. Additionally, presence of the compression bumps
124A-124D registered with individual fiber cores 134A-134D of the
multi-core optical fiber 130 may provide preferential transmission
paths for optical signals from individual cores of one multi-fiber
cable to individual cores of another multi-fiber cable (not
shown).
[0066] In certain embodiments, polymeric materials arranged in
contact with the terminal ends of optical fibers may include one or
more waveguide regions that are laterally embedded in a surrounding
material, with each waveguide region being configured to guide
light signals from a terminal end of an optical fiber to a
polymeric material outer end face. Presence of waveguide regions
serves to reduce insertion losses for optical signals transmitted
through polymeric material assemblies, and further enables parallel
transmission of multiple optical signals (e.g., through a
multi-core optical fiber) with reduction or elimination of
cross-talk. Preferably, a waveguide material of a waveguide region
has a first refractive index and a surrounding material has a
second refractive index that differs from the first refractive
index. In certain embodiments, at least one of the waveguide
material or the surrounding material may include OrmoStamp.TM.
hybrid polymer material (having a refractive index of 1.504) or
OrmoClear.TM. hybrid polymer material (having a refractive index of
1.538), with both of the foregoing materials being commercially
available from Micro Resist Technology GmbH (Berlin, Germany).
Other materials may be used, including materials having refractive
index values differing from the foregoing values.
[0067] In certain embodiments, each waveguide region includes a
transition portion having a variable cross-sectional diameter
(e.g., forming a conical or frustoconical shape), and a waveguiding
portion having a cross-sectional diameter that is smaller than an
average cross-sectional diameter of the transition portion. The
variable cross-sectional diameter of the transition portion may be
tapered (e.g., linear or non-linear), configured to match an
optical mode in a polymer waveguide to a fiber mode in the optical
fiber, and/or optimized to reduce insertion loss. The waveguiding
portion may include a cross-sectional diameter that is
substantially constant, or that is variable in character (i.e.,
having a diameter that varies with respect to position). Each
transition portion may be arranged proximate to an end face of an
optical fiber and/or an individual core of a multi-core optical
fiber. In certain embodiments, an end face of each transition
portion has a larger diameter than a diameter of an optical core
(or optical fiber) arranged to abut the transition portion. An
exemplary method for forming a waveguide region that includes a
waveguide material and a surrounding material may embody or include
three-dimensional printing. Optionally, at least one waveguide
region may be formed in a first step (e.g., a first 3D printing
step), and the surrounding material may be formed in a second step
(e.g., a second 3D printing step) to laterally surround the at
least one waveguide region. When at least one first waveguide
region is provided in an end portion of at least one internal bore
of a first ferrule of a first connector, the at least one first
waveguide region may be configured to mate with at least one second
waveguide region provided in an end portion of at least one
internal bore of a second ferrule of a second connector to provide
at least one signal transmission path therebetween. In certain
embodiments, multiple waveguide regions may be provided in an end
portion of a single bore of a ferrule configured to receive a
multi-core optical fiber, with each waveguide region being
registered with a terminal end of a different core of the
multi-core optical fiber.
[0068] FIG. 17 is a cross-sectional view of a polymeric material
assembly 150 suitable for fabrication in an internal bore of a
ferrule. The polymeric material assembly 150 includes an inner face
159 configured to abut a terminal end of a multi-core optical fiber
(e.g., as shown in FIG. 18), and includes an outer end face 152
configured to be positioned proximate to an end face of a polymeric
material assembly associated with another ferrule (e.g., as shown
in FIG. 19). With continued reference to FIG. 17, a lateral
boundary 162 of the polymeric material assembly 150, which may be
substantially cylindrical in shape, is arranged to contact an inner
surface defining an internal bore of a ferrule (not shown). The
polymeric material assembly 150 includes waveguide material shaped
into first and second waveguide regions 158-1, 158-2 that are
laterally embedded in a surrounding material 163. The first and
second waveguide regions 158-1, 158-2 each extend between the inner
face 159 and the outer end face 152. Each waveguide region 158-1,
158-2 includes a transition portion 156-1, 156-2 having a variable
cross-sectional diameter (e.g., forming a conical or frustoconical
shape). Each waveguide region 158-1, 158-2 also includes a
waveguiding portion 160-1, 160-2 having a substantially constant
cross-sectional diameter that is smaller than an average
cross-sectional diameter of the corresponding transition portion
156-1, 156-2. As shown in FIG. 17, each transition portion 156-1,
156-2 has a larger diameter end 154-1, 154-2 proximate to the inner
face 159 of the polymeric material assembly 150. Each transition
portion 156-1, 1-56-2 also has a diameter that tapers with distance
away from the inner face 159 to contact the corresponding
waveguiding portion 160-1, 160-2. Each waveguiding portion 160-1,
160-2 extends between the corresponding transition portion 156-1,
156-2 (at a smaller diameter end thereof) and the outer end face
152 of the polymeric material assembly 150. As shown, the outer end
face 152 of the polymeric material assembly 150 includes a central
surface portion 164 that protrudes slightly outward relative to
peripheral portions of the outer end face 152, such that the outer
end face 152 may be convex in shape. In certain embodiments, the
polymeric material assembly 150 is subject to being elastically
deformed when the outer end face 152 is compressed against a mating
surface (e.g., of another connector (not shown)). In this regard,
the slight protrusion of the central surface portion 164 relative
to a peripheral remainder of the outer end face 152 accommodates
deformation when the outer end face 152 of the polymeric material
assembly 150 is pressed against such a mating surface.
[0069] FIG. 18 is a cross-sectional view of the polymeric material
assembly 150 of FIG. 17 abutting a terminal end 132 of a multi-core
optical fiber 130 in the internal bore of a ferrule 172. For the
sake of brevity, descriptions of various elements of the polymeric
material assembly 150 previously recited in connection with FIG. 17
are incorporated by reference with respect to FIG. 18. As shown in
FIG. 18, the inner face 159 of the polymeric material assembly 150
is arranged in contact with the terminal end 132 of the multi-core
optical fiber 130. Each waveguide region 158-1, 158-2 of the
polymeric material assembly 150 extends between a terminal end of a
different fiber core 134-1, 134-2 and the outer end face 152
(encompassing an outwardly protruding central portion 164) of the
polymeric material assembly 150. As further shown in FIG. 18, each
waveguide region 158-1, 158-2 includes the corresponding transition
portion 156-1, 156-2 having a frustoconical shape with a larger
diameter end abutting an end of the corresponding fiber core 134-1,
134-2 of the multi-core optical fiber 130. Additionally, the larger
diameter end of each transition portion 156-1, 156-2 includes a
diameter that exceeds a diameter of the adjacent fiber core 134-1,
134-2. The fiber cores 134-1, 134-2 are distributed within a
surrounding glass material 136. Each transition portion 156-1,
156-2 is configured to convey optical signals received from a
corresponding fiber core 134-1, 134-2 to a waveguiding portion
160-1, 160-2 associated with the respective transition portion
156-1, 156-2.
[0070] FIG. 19 is a cross-sectional view of end portions of first
and second ferrules 172A, 172B (each embodying features according
to the ferrule 172 of FIG. 18) arranged to be mated with one
another. Each ferrule 172A, 172B contains a multi-core optical
fiber 130A, 130B having multiple fiber cores 134-1A, 134-2A,
134-1B, 134-2B distributed within a surrounding glass material
136A, 136B. Each ferrule 172A, 172B also contains a polymeric
material assembly 150A, 150B that includes a waveguide region
158-1A, 158-2A, 158-1B, 158-2B. Each waveguide region 158-1A,
158-2A, 158-1B, 158-2B is registered with a corresponding optical
fiber core 134-1A, 134-2A, 134-1B, 134-2B, with an inner face 159A,
159B of each polymeric material assembly 150A, 150B arranged in
contact with a terminal end 132A, 132B of the corresponding
multi-core optical fiber 130A, 130B. As shown, outwardly-protruding
central surface portions 164A, 164B of the polymeric material
assemblies 150A, 150B are arranged in contact with one another,
whereas peripheral remainders of outer end faces 152A, 152B are not
yet arranged in contact with one another. Following application of
compressive force to the ferrules 172A, 172B, end portions of the
polymeric material assemblies 150A, 150B may be deformed to provide
continuous contact between the peripheral remainders of the outer
end faces 152A, 152B.
[0071] In operation of the first and second ferrules 172A, 172B,
optical signals may be transmitted from fiber cores 134-1A, 134-2A
of the first ferrule 172A into waveguide regions 158-1A, 158-2A of
the first polymeric material assembly 150A, then into waveguide
regions 158-1B, 158-2B of the second polymeric material assembly
150B, and into fiber cores 134-1B, 134-2B of the second ferrule
172B. Additional optical signals may be transmitted in the reverse
direction. Utilization of the polymeric material assemblies 150A,
150B with corresponding waveguide regions 158-1A, 158-2A, 158-1B,
158-2B permits optical signals to be transmitted between fiber
cores 134-1A, 134-2A, 134-1B, 134-2B of multi-core optical fibers
130A, 130B with reduced crosstalk and reduced insertion loss.
Additionally, utilization of the polymeric material assemblies
150A, 150B permits optical communication with low insertion losses
without necessitating polishing of terminal ends 132A, 132B of the
multi-core optical fibers 130A, 130B.
[0072] FIG. 20 is a cross-sectional view of a prefabricated
polymeric material assembly 150 suitable for fabrication in an
internal bore of a ferrule. For the sake of brevity, descriptions
of various elements of the polymeric material assembly 150
previously recited in connection with FIG. 17 are incorporated by
reference with respect to FIG. 20, except where otherwise
noted.
[0073] The prefabricated polymeric material assembly 150 is
configured for insertion into the internal bore 19 of the ferrule
172 (shown in FIG. 21; discussed in more detail below). To
facilitate retention of the prefabricated polymeric material 150
assembly within the ferrule 172, the prefabricated polymeric
material assembly 150 includes a groove 174 (also referred to as a
chamber, cavity, recess, etc.) positioned along a perimeter of the
polymeric material to receive an adhesive therein. In certain
embodiments, the groove 174 may including one or more segments
forming a generally annular ring shape, wherein such segment(s) may
be continuous or non-continuous in character. In certain
embodiments, the groove 174 may comprise one or more chambers, such
as two chambers positioned on different lateral sides or sidewall
portions of the polymeric material.
[0074] FIG. 21 is a cross-sectional view of the prefabricated
polymeric material assembly 150 of FIG. 20 abutting a terminal end
132 of a multi-core optical fiber 130 in the internal bore 19 of
the ferrule 172. For the sake of brevity, descriptions of various
elements of the polymeric material assembly 150 previously recited
in connection with FIG. 20 are incorporated by reference with
respect to FIG. 21. Further, descriptions of similar elements
discussed in FIG. 18 are incorporated by reference with respect to
FIG. 21.
[0075] As shown, the prefabricated polymeric material assembly 150
is configured for insertion into the recess 70 of the internal bore
19 of the ferrule 172. In particular, the groove 174 is configured
to be filled with liquid adhesive 175 (e.g., epoxy). Accordingly,
once the prefabricated polymeric material assembly 150 is inserted
into and positioned within the internal bore 19 of the ferrule 172,
UV light is applied to activate (e.g., crosslink) the liquid
adhesive 175 to bond the prefabricated polymeric material assembly
150 to the ferrule 172.
[0076] FIG. 22 is a cross-sectional view of another embodiment of a
prefabricated polymeric material assembly 150 suitable for
fabrication in an internal bore of a ferrule. For the sake of
brevity, descriptions of various elements of the polymeric material
assembly 150 previously recited in connection with FIGS. 17 and 20
are incorporated by reference with respect to FIG. 22, except where
otherwise noted.
[0077] The prefabricated polymeric material assembly 150 in the
embodiment of FIG. 22 is still configured for insertion into the
internal bore 19 of the ferrule 172 (shown in FIG. 23; discussed in
more detail below). To facilitate assembly therebetween, the
prefabricated polymeric material assembly 150 includes the groove
174 (discussed above) as well as a plurality of cavities 176-1,
176-2 defined in the inner face 159 thereof. Each cavity 176-1,
176-2 has a variable cross-sectional diameter (e.g., forming a
conical or frustoconical shape). Unlike the polymeric material
assembly 150 of FIGS. 17 and 20, the first and second waveguide
regions 158-1, 158-2 only include waveguiding portions 160-1, 160-2
(and not transition portions 156-1, 156-2). In this way, the first
and second waveguide regions 158-1, 158-2 each extend from the
outer end face 152 to the plurality of cavities 176-1, 176-2, where
each cavity 176-1, 176-2 is generally aligned with the first and
second waveguide regions 158-1, 158-2, respectively. Each cavity
176-1, 176-2 has a larger diameter end 178-1, 178-2 proximate to
the inner face 159 of the prefabricated polymeric material assembly
150. Each cavity 176-1, 176-2 also has a diameter that tapers with
distance away from the inner face 159 to contact the corresponding
waveguiding portion 160-1, 160-2. Each waveguiding portion 160-1,
160-2 extends between the corresponding cavity 176-1, 176-2 (at a
smaller diameter end thereof) and the outer end face 152 of the
prefabricated polymeric material assembly 150.
[0078] FIG. 23 is a cross-sectional view of the prefabricated
polymeric material assembly 150 of FIG. 22 abutting a terminal end
132 of a multi-core optical fiber 130 in the internal bore 19 of
the ferrule 172. For the sake of brevity, descriptions of various
elements of the polymeric material assembly 150 previously recited
in connection with FIG. 22 are incorporated by reference with
respect to FIG. 23. Further, descriptions of similar elements
discussed in FIGS. 18 and 21 are incorporated by reference with
respect to FIG. 23.
[0079] As shown, the prefabricated polymeric material assembly 150
is configured for insertion into the recess 70 of the internal bore
19 of the ferrule 172. In particular, the groove 174 is configured
to be filled with liquid adhesive 175 (e.g., epoxy), and the
cavities 176-1, 176-2 are configured to be filled with a liquid,
curable polymer material 180-1, 180-2 (e.g., an inorganic-organic
hybrid polymer such as described in the examples discussed above,
and optionally the same material as (or a material similar to) the
material of the prefabricated polymeric material assembly 150).
Accordingly, once the prefabricated polymeric material assembly 150
is inserted into and positioned within the internal bore 19 of the
ferrule 172, UV light is applied to activate (e.g., crosslink) the
liquid adhesive 175 to bond the prefabricated polymeric material
assembly 150 to the ferrule 172. Additionally, the UV light serves
to bond the prefabricated polymeric material assembly 150 to the
fiber cores 134-1, 134-2. Accordingly, the fiber cores 134-1, 134-2
are bonded to the first and second wave guide regions 158-1,
158-2.
[0080] In certain embodiments, fiber optic connectors and
fabrication methods disclosed herein may apply to multiple fibers
(e.g., multi-fiber cables).
[0081] FIGS. 24 and 25 are views of a fiber optic connector and an
associated fiber optic cable forming a fiber optic cable assembly,
with the fiber optic connector including a multi-fiber ferrule with
a single ferrule boot. Persons skilled in the field of optical
connectivity will appreciate that the connector 182 is merely an
example, and that the general principles disclosed with respect to
the multi-fiber ferrules and other components may also be
applicable to other connector designs.
[0082] As shown in FIG. 24, the connector 182 may be installed on a
fiber optic cable 184 ("cable") to form a fiber optic cable
assembly 186. The connector 182 includes a ferrule 188, a housing
190 received over the ferrule 188, a slider 192 received over the
housing 190, and a boot 194 received over the cable 184. The
ferrule 188 is spring-biased within the housing 190 so that a front
portion 196 of the ferrule 188 extends beyond a front end 198 of
the housing 190. Optical fibers (not shown) carried by the cable
184 extend through bores 200 (also referred to as micro-holes)
defined in the ferrule 188 before terminating at or near a front
end face 202 of the ferrule 188. The optical fibers are restrained
within the ferrule 188 as described above, such as by using an
adhesive material (e.g., epoxy). The optical fibers can be
presented for optical coupling with optical fibers of a mating
component (e.g., another fiber optic connector; not shown) when the
housing 190 is inserted into an adapter, receptacle, or the
like.
[0083] As shown in FIG. 25, the connector 182 also includes a
ferrule boot 204, guide pin assembly 206, spring 208, crimp body
210, and crimp ring 212. The ferrule boot 204, which is unitary in
character, is received in a rear portion 214 of the ferrule 188 to
help support the optical fibers extending to the ferrule bores 200
(shown in FIG. 24). In particular, optical fibers extend through an
aperture (not shown) defined through the ferrule boot 204. The
guide pin assembly 206 includes a pair of guide pins 216 extending
from a pin keeper 218. Features on the pin keeper 218 cooperate
with features on the guide pins 216 to retain portions of the guide
pins 216 within the pin keeper 218. When the connector 182 is
assembled, the pin keeper 218 is positioned against a back surface
of the ferrule 188, and the guide pins 216 extend through pin holes
220 (shown in FIG. 24) provided in the ferrule 188 so as to project
beyond the front end face 202 of the ferrule 188.
[0084] Both the ferrule 188 and guide pin assembly 206 are biased
to a forward position relative to the housing 190 by the spring
208. More specifically, the spring 208 is positioned between the
pin keeper 218 and a portion of the crimp body 210. The crimp body
210 is inserted into the housing 190 when the connector 182 is
assembled and includes latching arms 222 that engage recesses 224
in the housing 190. The spring 208 is compressed by this point and
exerts a biasing force on the ferrule 188 via the pin keeper 218.
The rear portion 214 of the ferrule 188 defines a flange that
interacts with a shoulder or stop formed within the housing 190 to
retain the rear portion 214 of the ferrule 188 within the housing
190. The rear portion 214 of the ferrule 188 also includes a recess
(not shown) configured to receive at least a front portion of the
ferrule boot 204.
[0085] In a manner not shown in the figures, aramid yarn or other
strength members from the cable 184 are positioned over an end
portion 226 of the crimp body 210 that projects rearwardly from the
housing 190. The aramid yarn is secured to the end portion 226 by
the crimp ring 212, which is slid over the end portion 226 and
deformed after positioning the aramid yarn. The boot 194 covers
this region, as shown in FIG. 24, and provides strain relief for
optical fibers emanating from the fiber optic cable 184 by limiting
the extent to which the connector 182 can bend relative to the
fiber optic cable 184.
[0086] Although the ferrule 188 includes a surface embodying a flat
front end face 202, in certain embodiments, one or more portions of
the front end face 202 may protrude forwardly from such a surface
to form one or more pedestals through which multiple bores (such as
bores 200 shown in FIG. 24) extend. Similarly, although the front
end face 202 of the ferrule 188 shown in FIG. 24 includes multiple
bores 200 that are equally spaced to form a one-dimensional array,
in certain embodiments, multiple groups of bores may extend through
a front end face with one or more solid regions, free of bores,
provided between such groups of bores. Additionally, in certain
embodiments, multiple rows of bores may be provided.
[0087] FIG. 26 is a cross-sectional view of the multi-fiber ferrule
188 with polymeric material protrusions 230-1 to 230-12 (which may
also be referred to as compression bumps, compression spots, etc.)
of different lengths (aligned with optical fibers 228-1 to 228-12
and extending outward past the front end face 202 at different
distances (also referred to as protrusion heights). In particular,
the length of each polymeric material protrusion 230-1 to 230-12
(and resulting protrusion height) may depend on the compression
force. For example, for ferrules of an MPO connector, the inner
optical fibers experience a different (e.g., decreased) compression
force than the outer optical fibers. Multi-fiber ferrule 188 may
compensate for this difference by varying the protrusion height
profile of the polymeric material protrusions 230-1 to 230-12. As
an example, the protrusion height profile of the polymeric material
protrusions 230-1 to 230-12 may be varied such that the outer
polymeric material protrusions 230-1 and 230-12 are shorter than
the inner polymeric material protrusions 230-6 and 230-7 (and,
therefore, have shorter protrusion heights), so that the inner
polymeric material protrusions 230-6 and 230-7 will experience
substantially the same compression force as the outer polymeric
material protrusions 230-1 and 230-12. This is difficult, if even
possible, for ferrules with multiple optical fibers that have been
processed (e.g., cleaved and/or polished) as a group for optical
communication. Although the foregoing example referred to a goal of
providing substantially uniform compression force for different
optical fibers, it is to be appreciated that principle described
herein may be utilized to provide any desired profile of
compression force with respect to position of individual optical
fibers associated with a multi-fiber ferrule or similar
element.
[0088] Utilization of waveguiding regions within polymeric material
assemblies configured to provide physical contact through an
optical interface may reduce insertion loss, such that a distance
between terminal ends of optical fibers (or optical fiber cores
thereof) may be increased relative to the use of polymeric
materials lacking waveguide regions while still providing
acceptably low insertion losses. For example, polymeric material
assemblies incorporating waveguide regions registered with
overlying terminal ends of optical fibers (or optical fiber cores
thereof) may have lengths in a range of from about 0.5 .mu.m to
about 50 .mu.m without introducing excessive insertion losses.
Accordingly, in certain embodiments, polymeric material regions
overlying terminal ends of optical fibers may have lengths in a
range of from about 0.5 .mu.m to about 50 .mu.m.
[0089] At least certain embodiments of the present disclosure
directed to fabrication methods may provide technical benefits
including one or more of the following: (A) eliminating the need to
polish terminal ends of optical fibers utilized in fiber optic
connectors while still providing physical contact through an
optical interface; (B) allowing precise and controlled shape
generation to create end faces suitable for making physical contact
through an optical interface; (C) eliminating the need to precisely
cut optical fiber ends to allow creation of angled end faces
suitable for providing physical contact through an optical
interface; (D) enabling creation and adjustment of protrusions and
undercuts for appropriate requirements within tolerances smaller
than may be obtained by conventional glass processing techniques;
(E) enabling reduction in tolerances for centering of terminal ends
of optical fibers; (F) enabling process automation for single-fiber
and multi-fiber connectors; and/or (G) enabling adjustment of the
height of end faces (e.g., to provide substantially uniform
compression force, or any desired profile of compression force with
respect to position of individual optical fibers).
[0090] At least certain embodiments of the present disclosure
directed to products (e.g., fiber optic connectors) may provide
technical benefits including one or more of the following: (A)
enabling reduction of compressive mechanical loads required to
provide physical contact of end faces of connectors incorporating
optical fibers; (B) increasing uniformity of optical fiber end face
shapes and conditions in nanometer scale; (C) enabling of reduced
insertion losses; (D) increasing reliability of connections, with
particular relevance to multi-core optical fibers; (E) enabling
formation of functional regions such as scratch resistance layers,
anti-reflection layers, anti-static layers, and/or lens regions
between a terminal end of an optical fiber and an end face that
provides physical contact through an optical interface.
[0091] Those skilled in the art will appreciate that other
modifications and variations can be made without departing from the
spirit or scope of the invention. Since modifications,
combinations, sub-combinations, and variations of the disclosed
embodiments incorporating the spirit and substance of the invention
may occur to persons skilled in the art, the invention should be
construed to include everything within the scope of the appended
claims and their equivalents. The claims as set forth below are
incorporated into and constitute part of this detailed
description.
[0092] It will also be apparent to those skilled in the art that
unless otherwise expressly stated, it is in no way intended that
any method in this disclosure be construed as requiring that its
steps be performed in a specific order. Accordingly, where a method
claim below does not actually recite an order to be followed by its
steps or it is not otherwise specifically stated in the claims or
descriptions that the steps are to be limited to a specific order,
it is no way intended that any particular order be inferred.
Moreover, where a method claim below does not explicitly recite a
step mentioned in the description above, it should not be assumed
that the step is required by the claim.
* * * * *