U.S. patent application number 13/782759 was filed with the patent office on 2013-07-11 for expanded beam connector concepts.
This patent application is currently assigned to COMMSCOPE, INC. OF NORTH CAROLINA. The applicant listed for this patent is COMMSCOPE, INC. OF NORTH CAROLINA. Invention is credited to Timothy W. Anderson, Matthew Cruz, Gary Gibbs, Jeffrey D. Nielson.
Application Number | 20130177280 13/782759 |
Document ID | / |
Family ID | 48743990 |
Filed Date | 2013-07-11 |
United States Patent
Application |
20130177280 |
Kind Code |
A1 |
Nielson; Jeffrey D. ; et
al. |
July 11, 2013 |
Expanded Beam Connector Concepts
Abstract
A terminus for a fiber optic cable includes a ferrule. In one
embodiment, an optical fiber of the cable passes through a central
bore of the ferrule and is attached to a lens seated in a conical
or cylindrical seat formed in an end surface of the ferrule by an
epoxy. In a second embodiment, an optical fiber of the cable passes
through the central bore of the ferrule. Next, a cap sleeve with a
lens therein is slid over and attached to the ferrule such that the
lens abuts or is attached to the optical fiber. In either
embodiment, an inspection slot may optionally be formed in the
ferrule and/or the cap sleeve to allow a technician to inspect the
state of the attachment and/or abutment and/or spacing of the
optical fiber and the lens.
Inventors: |
Nielson; Jeffrey D.; (Wylie,
TX) ; Gibbs; Gary; (Wylie, TX) ; Cruz;
Matthew; (Council Bluffs, IA) ; Anderson; Timothy
W.; (Omaha, NE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
COMMSCOPE, INC. OF NORTH CAROLINA; |
Hickory |
NC |
US |
|
|
Assignee: |
COMMSCOPE, INC. OF NORTH
CAROLINA
Hickory
NC
|
Family ID: |
48743990 |
Appl. No.: |
13/782759 |
Filed: |
March 1, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12337212 |
Dec 17, 2008 |
8393804 |
|
|
13782759 |
|
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|
|
11765318 |
Jun 19, 2007 |
7604417 |
|
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12337212 |
|
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60814527 |
Jun 19, 2006 |
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Current U.S.
Class: |
385/79 |
Current CPC
Class: |
G02B 6/32 20130101; G02B
6/3878 20130101; G02B 6/322 20130101; G02B 6/3874 20130101; G02B
6/262 20130101; G02B 6/3885 20130101; G02B 1/11 20130101; G02B
6/3869 20130101; G02B 6/382 20130101; G02B 6/3882 20130101; G02B
6/36 20130101; G02B 6/3849 20130101; G02B 6/3861 20130101; G02B
6/3853 20130101; G02B 6/3821 20130101 |
Class at
Publication: |
385/79 |
International
Class: |
G02B 6/36 20060101
G02B006/36 |
Claims
1. A fiber optic cable apparatus comprising: a ferrule having a
bore passing from a first end to a second end; an optical fiber
passing through said bore of said ferrule, said optical fiber
having a termination end proximate said second end of said ferrule;
a sleeve sized to fit over said second end of said ferrule and
directly contact said ferrule for attachment thereto; a lens within
said cap sleeve, wherein said lens resides proximate said second
end of said ferrule when said cap sleeve is attached to said
ferrule, wherein the portion of said lens that resides proximate
said second end of said ferrule includes a flat surface; and an
optical epoxy connecting said termination end of said optical fiber
to said lens, such that light exiting said termination end of said
optical fiber passes through said optical epoxy prior to entering
into said lens.
2. The fiber optic cable apparatus according to claim 1, wherein
said ferrule and said cap sleeve are formed of a ceramic
material.
3. The fiber optic cable apparatus according to claim 1, wherein
said optical fiber is generally cylindrical in shape with a first
diameter and said lens is generally spherical in shape, apart from
said flat surface, and has a second diameter, which is greater than
said first diameter.
4. The fiber optic cable apparatus according to claim 3, wherein
said second diameter is at least three times greater than said
first diameter.
5. The fiber optic cable apparatus according to claim 1, wherein
said lens is formed of a material different from said optical
fiber, wherein said material forming said optical fiber has a first
index of refraction which is less than 1.6 and said material
forming said lens has an index of refraction which is greater than
said first index of refraction.
6. The fiber optic cable apparatus according to claim 1, wherein
said lens is formed of a material different from said optical
fiber, wherein said material forming said lens has a first index of
refraction which is greater than 1.5 and a material forming said
optical fiber has an index of refraction which is less than said
first index of refraction.
7. The fiber optic cable apparatus according to claim 1, wherein
said lens is formed of sapphire.
8. The fiber optic cable apparatus according to claim 1, further
comprising: an inspection slot formed in said cap sleeve proximate
said lens which affords a view of an area between said lens and
said second end of said ferrule when said cap sleeve is attached to
said ferrule.
9. The fiber optic cable apparatus according to claim 1, wherein no
portion of said lens within said cap sleeve protrudes past an end
face of said cap sleeve.
10. The fiber optic cable apparatus according to claim 1, further
comprising: a retaining sleeve sized to fit over said first end of
said ferrule and directly contact said ferrule for attachment
thereto.
11. The fiber optic cable apparatus according to claim 10, wherein
said retaining sleeve includes a through slot which affords access
to an area adjacent said first end of said ferrule when said
retaining sleeve is attached to said ferrule.
12. The fiber optic cable apparatus according to claim 1, further
comprising: a connector envelope supporting said ferrule and said
cap sleeve.
13. A fiber optic cable apparatus comprising: a ferrule having a
bore passing from a first end to a second end; an optical fiber
passing through said bore of said ferrule, said optical fiber
having a termination end proximate said second end of said ferrule;
a sleeve sized to fit over said second end of said ferrule and
directly contact said ferrule for attachment thereto; a lens within
said cap sleeve, wherein said lens resides proximate said second
end of said ferrule when said cap sleeve is attached to said
ferrule, wherein said lens is a barrel lens; and an optical epoxy
connecting said termination end of said optical fiber to said
barrel lens, such that light exiting said termination end of said
optical fiber passes through said optical epoxy prior to entering
into said barrel lens.
14. The fiber optic cable apparatus according to claim 13, wherein
said barrel lens has a generally cylindrical mid-region and
includes a first convex surface on a first end of said generally
cylindrical mid region.
15. The fiber optic cable apparatus according to claim 14, wherein
said barrel lens includes a second convex surface on an opposite,
second end of said generally cylindrical mid-region.
16. The fiber optic cable apparatus according to claim 15, wherein
said generally cylindrical mid-region has a diameter which is
approximately equal to an inner diameter of said cap sleeve.
17. The fiber optic cable apparatus according to claim 16, wherein
said barrel lens is attached to said cap sleeve by an epoxy.
18. The fiber optic cable apparatus according to claim 17, wherein
a portion of said barrel lens protrudes past an end face of said
cap sleeve.
19. A fiber optic cable apparatus comprising: a ferrule having a
bore passing from a first end to a second end; an optical fiber
passing through said bore; and a lens attached to said second end
of said ferrule and attached to said optical fiber, wherein said
second end includes a recessed seat, and wherein said lens resides
in said recessed seat, and wherein said lens has a size which is
less than a depth of said recessed seat, such that said lens does
not protrude past a plane of said second end of said ferrule,
wherein said lens is distanced from an end of said optical fiber
and the attachment between said lens and said optical fiber is made
by an epoxy having optical characteristics and wherein said lens
has an index of refraction which is greater than an index of
refraction of said optical fiber.
20. The fiber optic cable apparatus of claim 19, wherein said lens
has an index of refraction great than 1.6.
Description
[0001] This application is a continuation-in-part of application
Ser. No. 12/337,212, filed Dec. 17, 2008, which is a
continuation-in-part of application Ser. No. 11/765,318, filed Jun.
19, 2007, which claims the benefit of U.S. Provisional Application
No. 60/814,527, filed Jun. 19, 2006, the entire contents of the
three prior applications are herein incorporated by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to fiber optic communications.
More particularly, the present invention relates to a terminus to
provide an orderly termination of a fiber optic cable, and to
structures incorporating one or more of the termini, such as a
connector, jumper, or attenuator.
[0004] 2. Description of the Related Art
[0005] It is known in the background art, that a fiber optic cable
may be cut and terminated for connection to a connector, jumper or
attenuator, or other such structure. A typical termination includes
a ferrule having a central bore passing through a center thereof. A
length of optical fiber is exposed at the end of the cut fiber
optic cable. The optical fiber is passed through the central bore
in the ferrule and cut flush with the end of the ferrule. An epoxy
secures the optical fiber within the central bore, and the cut end
of the optical fiber is polished, along with the end of the
ferrule, to finish the termination.
[0006] There was an appreciation in the background art that such a
typical termination was unsuitable for use in harsh environments
which are prone to vibration, such as in an aircraft. Since the
optical fiber extended to the end of the ferrule and made physical
contact with a receiving structure, the optical fiber was
susceptible to damage (e.g. small stress cracks) when vibrated.
U.S. Pat. No. 6,074,100, which is herein incorporated by reference,
addressed this physical contact drawback associated with the
typical termination.
[0007] FIGS. 17-21 illustrate the terminus of U.S. Pat. No.
6,074,100. In FIG. 17, the fiber optic cable 208 is stripped to
remove and expose several sheaths of cable material. The stripped
end of the fiber optic cable 208 includes a central optical fiber
212, a silicon buffer 214 disposed about the optical fiber 212, an
inner jacket 216 enveloping the silicon buffer 214, a strengthening
member 218 comprising a braided or woven fiber, e.g., a polyamide
fiber such as Kevlar.RTM., wrapped about the inner jacket 216, and
an outer jacket 220 enveloping the strengthening member 218.
[0008] In FIG. 18, the stripped end of the fiber optic cable 208 is
prepared for bonding to a ferrule assembly 222. The ferrule
assembly 222 includes a rigid ferrule 224 and an aft body or sleeve
226 circumscribing and bonded to an end portion of the ferrule 224.
More specifically, the rigid ferrule 224 defines an external face
surface 228, a central bore 230 and an internal end 232, and the
aft body 226 comprises a cylindrical inner bore 234 and a tapered
end 236 defining a cylindrical outer surface 238. The ferrule 224
is fabricated from a ceramic, such as zirconia, and the aft body
226 is fabricated from stainless steel.
[0009] In preparation for bonding, a bead or ring of bonding
adhesive 240 is applied to the outer surface 238 of the aft body
226, corresponding to region A, and a layer of bonding adhesive
242, corresponding to region B, is applied to the optical fiber 212
and inner jacket 214. The bonding adhesives 240, 242 in regions A
and B are the same and, furthermore, are selected such that the
Glass Transition Temperature (T.sub.G) is greater than the maximum
temperature anticipated in the operating environment of the
terminus. Prior to bonding, the strengthening members 218 are
folded rearwardly over the outer jacket 220. A shrink tubing 244,
which will subsequently overlay the strengthening member 218, is
used to temporarily preposition the strengthening member 218 over
the outer jacket 220.
[0010] In FIG. 19, the stripped end of the fiber optic cable 208 is
inserted within the ferrule assembly 222 such that the optical
fiber 212 passes through the ferrule bore 230 and the inner jacket
214 abuts the internal end 232 of the ferrule 224. Next, the shrink
tubing 244 is slid rearwardly (shown in phantom) to release the
strengthening member 218 which is then folded over the cylindrical
outer surface 238 of the aft body 226. As such, the ring of bonding
adhesive 240 in region A contacts and impregnates the strengthening
member 218. The shrink tubing 244 is then moved forwardly such that
it overlays the strengthening member 218 and the outer jacket 220.
During a curing process, the adhesive 240 is solidified and the
shrink tube 244 contracts. After the curing process, the end of the
optical fiber 212 is cleaved in close proximity to the external
face surface 228 of the ferrule 224, as illustrated in FIG. 19.
[0011] Then, various sanding or polishing operations are preformed
in order to recess the cut end of the optical fiber 212 below the
external face surface 228 of the ferrule 224, as illustrated in
FIGS. 20 and 21. Specifically, the end profile 250 is characterized
by the optical fiber 212 defining an end surface 252 which is
recessed or undercut relative to the face surface 228 of the
ferrule 224 (as best shown in FIG. 20). The end surface of the
optical fiber 212 is at least the combination of the light-carrying
core 212.sub.CO and its surrounding cladding 212.sub.CL.
[0012] By the arrangement of FIGS. 17-21, U.S. Pat. No. 6,074,100
provides a fiber optic cable termination more suitable for use in a
demanding operational environment prone to vibration. By recessing
the optical fiber termination 252 to a point within the ferrule end
228, the optical fiber was no longer in direct physical contact
with a light transmission/reception structure (e.g., another
optical fiber end or detector lens) and hence was less susceptible
to damage (e.g., cracks in the optical fiber).
SUMMARY OF THE INVENTION
[0013] The Applicants have appreciated drawbacks in the terminus of
the prior art.
[0014] With a physical contact (PC) connector, if a technician
unintentionally snags the cordage entering the PC connector while
working with tools, the ferrule holding the optical fiber can
slightly retract into the connector body against a spring bias. If
the ferrule retracts more than 1/2 of a wavelength of the signal,
the signal connection will be lost. In ships, airplanes,
submarines, etc., loss of the signal can be a trigger to reset
computer equipment or to proceed to an emergency program. Either
circumstance can be dangerous.
[0015] Also with prior art PC connectors, the connection is highly
susceptible to dirt and dust. The presence of dirt and/or dust in
the vicinity of the optical fiber of the ferrule can cause the
connector to fail. For example, a small particle of debris can
easily obstruct the light path which may be as small as eight
microns in diameter.
[0016] Applicants have also appreciated that having several
different terminus structures for different type end structures
(e.g., connectors, jumpers, attenuators) is inefficient. Such
arrangements of the background art require designing, tooling and
inventorying many different parts. Moreover, technicians must be
trained to install several different types of terminus and must
carry different types of specialty tools for differently structured
termini.
[0017] Also, Applicants have appreciated that many of the termini
of the background art are difficult to install at the end of the
fiber optic cable, insecure in their attachment to the end of the
cable, and insecure in their attachment to the end structure (e.g.,
connector, jumper) and exhibit variable performance characteristics
(e.g., dB losses at the terminus are widely inconsistent as
installed and can change with vibration of the terminus).
[0018] The present invention addresses one or more of the drawbacks
of the prior art.
[0019] These and other objects are accomplished by a terminus for a
fiber optic cable including a ferrule. In one embodiment, an
optical fiber of the cable passes through a central bore of the
ferrule and is attached to a lens seated in a conical or
cylindrical seat formed in an end surface of the ferrule by an
epoxy. In a second embodiment, an optical fiber of the cable passes
through the central bore of the ferrule. Next, a cap sleeve with a
lens therein is slid over and attached to the ferrule such that the
lens abuts or is attached to the optical fiber. In either
embodiment, an inspection slot may optionally be formed in the
ferrule and/or the cap sleeve to allow a technician to inspect the
state of the attachment and/or abutment and/or spacing of the
optical fiber and the lens.
[0020] Further scope of applicability of the present invention will
become apparent from the detailed description given hereinafter.
However, it should be understood that the detailed description and
specific examples, while indicating preferred embodiments of the
invention, are given by way of illustration only, since various
changes and modifications within the spirit and scope of the
invention will become apparent to those skilled in the art from
this detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] The present invention will become more fully understood from
the detailed description given hereinbelow and the accompanying
drawings which are given by way of illustration only, and thus, are
not limits of the present invention, and wherein:
[0022] FIG. 1 is a cross sectional side view of a terminus in
accordance with a first embodiment of the present invention;
[0023] FIG. 2 is a top view illustrating an end portion of the
ferrule of FIG. 1;
[0024] FIG. 3 is a side view, illustrating the end portion of the
ferrule of FIG. 1;
[0025] FIG. 4 is an end view of the ferrule of FIG. 1;
[0026] FIG. 5 is a cross sectional view illustrating a jumper
formed by a length of fiber optic cable with ferrules, as depicted
in FIG. 1, attached at each end;
[0027] FIG. 5A is a cross sectional view similar to FIG. 1, but
illustrating an alternative design for the first embodiment of the
terminus;
[0028] FIG. 5B is a side view similar to FIG. 3, but illustrating
yet another alternative design for the first embodiment of the
terminus with alternative retaining features;
[0029] FIG. 6 is a cross sectional side view of an ST fiber optic
connector including a terminus in accordance with FIG. 5A;
[0030] FIG. 7 is a top view of a first embodiment of an MT
connector including a plurality of termini in accordance with the
first embodiment of the present invention;
[0031] FIG. 7A is an end view of the MT connector of FIG. 7;
[0032] FIG. 8 is a top view of an alternative embodiment of an MT
connector including a plurality of termini in accordance with the
first embodiment of the present invention;
[0033] FIG. 8A is an end view of the MT connector of FIG. 8;
[0034] FIG. 9 is a perspective view of a ferrule and retaining
sleeve for a terminus in accordance with a second embodiment of the
present invention;
[0035] FIG. 10 is a side view of the ferrule and retaining sleeve
of FIG. 9;
[0036] FIG. 11 is an end view of the ferrule and retaining sleeve
of FIGS. 9 and 10;
[0037] FIG. 12 is a cross sectional view taken along line XII-XII
in FIG. 11;
[0038] FIG. 13 is a perspective view of a cap sleeve for a terminus
in accordance with the second embodiment of the present
invention;
[0039] FIG. 14 is a perspective view of the cap sleeve of FIG. 13
slid over the ferrule of FIG. 9;
[0040] FIG. 15 is a cross sectional view taken along line XV-XV in
FIG. 14, FIG. 15A is a close-up cross sectional view showing a lens
in the shape of a sphere with a flat surface in the end of the cap
sleeve, FIG. 15B is a perspective view of a barrel lens, FIG. 15C
is a close-up cross sectional view of the barrel lens in the end of
the cap sleeve, and FIG. 15D is a side view of an extended length
barrel lens;
[0041] FIG. 16 is a cross sectional view similar to FIG. 15, but
illustrating an alternative embodiment for the cap sleeve and
mounting of a lens within the cap sleeve;
[0042] FIG. 17 is a side view, partially in cross section,
illustrating an end of a fiber optic cable which has been stripped
to reveal an optical fiber, in accordance with the prior art;
[0043] FIG. 18 is a side view, partially in cross section,
illustrating the stripped end of FIG. 17 prepared for bonding to a
ferrule assembly, in accordance with the prior art;
[0044] FIG. 19 illustrates the bonding of the stripped end to the
ferrule assembly to form a terminus, in accordance with the prior
art;
[0045] FIG. 20 is a cross sectional side view of the end of the
terminus of FIG. 19 subsequent to a polishing operation; and
[0046] FIG. 21 is a cross sectional close-up view of the optical
fiber at the end of the terminus of FIG. 20.
DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION
[0047] The present invention now is described more fully
hereinafter with reference to the accompanying drawings, in which
embodiments of the invention are shown. This invention may,
however, be embodied in many different forms and should not be
construed as limited to the embodiments set forth herein; rather,
these embodiments are provided so that this disclosure will be
thorough and complete, and will fully convey the scope of the
invention to those skilled in the art.
[0048] Like numbers refer to like elements throughout. In the
figures, the thickness of certain lines, layers, components,
elements or features may be exaggerated for clarity. Broken lines
illustrate optional features or operations unless specified
otherwise.
[0049] The terminology used herein is for the purpose of describing
particular embodiments only and is not intended to be limiting of
the invention. Unless otherwise defined, all terms (including
technical and scientific terms) used herein have the same meaning
as commonly understood by one of ordinary skill in the art to which
this invention belongs. It will be further understood that terms,
such as those defined in commonly used dictionaries, should be
interpreted as having a meaning that is consistent with their
meaning in the context of the specification and relevant art and
should not be interpreted in an idealized or overly formal sense
unless expressly so defined herein. Well-known functions or
constructions may not be described in detail for brevity and/or
clarity.
[0050] As used herein, the singular forms "a", "an" and "the" are
intended to include the plural forms as well, unless the context
clearly indicates otherwise. It will be further understood that the
terms "comprises" and/or "comprising," when used in this
specification, specify the presence of stated features, integers,
steps, operations, elements, and/or components, but do not preclude
the presence or addition of one or more other features, integers,
steps, operations, elements, components, and/or groups thereof. As
used herein, the term "and/or" includes any and all combinations of
one or more of the associated listed items. As used herein, phrases
such as "between X and Y" and "between about X and Y" should be
interpreted to include X and Y. As used herein, phrases such as
"between about X and Y" mean "between about X and about Y." As used
herein, phrases such as "from about X to Y" mean "from about X to
about Y."
[0051] It will be understood that when an element is referred to as
being "on", "attached" to, "connected" to, "coupled" with,
"contacting", etc., another element, it can be directly on,
attached to, connected to, coupled with or contacting the other
element or intervening elements may also be present. In contrast,
when an element is referred to as being, for example, "directly
on", "directly attached" to, "directly connected" to, "directly
coupled" with or "directly contacting" another element, there are
no intervening elements present. It will also be appreciated by
those of skill in the art that references to a structure or feature
that is disposed "adjacent" another feature may have portions that
overlap or underlie the adjacent feature.
[0052] Spatially relative terms, such as "under", "below", "lower",
"over", "upper", "lateral", "left", "right" and the like, may be
used herein for ease of description to describe one element or
feature's relationship to another element(s) or feature(s) as
illustrated in the figures. It will be understood that the
spatially relative terms are intended to encompass different
orientations of the device in use or operation in addition to the
orientation depicted in the figures. For example, if the device in
the figures is inverted, elements described as "under" or "beneath"
other elements or features would then be oriented "over" the other
elements or features. The device may be otherwise oriented (rotated
90 degrees or at other orientations) and the descriptors of
relative spatial relationships used herein interpreted
accordingly.
[0053] FIG. 1 is a cross sectional side view of a terminus 3 in
accordance with the present invention. The terminus 3 includes a
ferrule 5. The ferrule 5 is generally cylindrical in shape, made of
ceramic (e.g., zirconia, glass, alumina), and has an outside
diameter of 1.25 mm. Of course, other shapes, sizes and materials
(such as a metal, a polymer or a composite material) may be
selected for the ferrule 5.
[0054] A first end 7 of the ferrule 5 includes a first conical
entrance 9. A second end 11 of the ferrule 5 includes a second
conical entrance 13. Although a conical shape is illustrated, the
shape could be cylindrical or any other type of shape resulting
from a counter bore within the second end 11 of the ferrule 5. The
first and second conical entrances 9 and 13 are generally centered
in the first and second ends 7 and 11, respectively. A bore 15
passes through the center of the ferrule 5 from a center of the
first conical entrance 9 to a center of the second conical entrance
13.
[0055] A retaining feature, such as a narrow ring or trench 17 may
be cut into an outer surface of the ferrule 5 to encircle the outer
surface of the ferrule 5. A retainer ring 19 removably resides
within the trench 17. The retainer ring 19 may be formed of metal,
a polymer or a composite. In preferred embodiments, the retainer
ring 19 is a spring clip or a rubber O-ring. The retainer ring 19
plays a role in attaching the terminus 3 to other structures (e.g.
a connector, a jumper), and may be located at other locations on
the ferrule 5. An alternative, differently structured retaining
feature is described in relation to FIG. 5B below.
[0056] The second end 11 of the ferrule 5 includes an inspection
slot 45 and a chamfer 47, as best seen in FIGS. 2-4. The inspection
slot 45 is a cutout in the material of the ferrule 5, which passes
down to the bore 15. The inspection slot 45 may be formed with a
diamond saw blade or by other means. The function of the inspection
slot 45 will be described below.
[0057] The terminus 3 also includes a retaining sleeve 21. The
retaining sleeve 21 is generally cylindrical in shape, made of
metal (such as stainless steel), and has an inner diameter
approximately equal to or slightly greater than 1.25 mm (i.e.
slightly greater than the outer diameter of the ferrule 5). Of
course, the retaining sleeve 21 could be made of other materials,
such as ceramic, polymer or composite materials. Also, the
retaining sleeve 21 could be differently shaped and sized, so long
as the ferrule 5 could be registered into the retaining sleeve 21,
as illustrated in FIG. 1.
[0058] Now, a use of the terminus 3 in conjunction with a fiber
optic cable or cordage 31 will be described. First, the cordage 31
is passed through the retaining sleeve 21. Next, an outer layer of
the cordage 31 is removed to expose a section of the light carrying
fiber 33 (approximately as long as the ferrule 5) and a short
section of the cable strength members, e.g., KEVLAR fibers 35,
which surround the light carrying optical fiber 33 (as depicted in
FIG. 1).
[0059] The light carrying optical fiber 33 is inserted into the
bore 15 at the first end 7 of the ferrule 5 using the first conical
entrance 9 as a guide. The optical fiber 33 is passed through the
bore 15 to the second end 11 of the ferrule 5 and stops at the
second conical entrance 13.
[0060] An optical epoxy 37 is applied to the end of the optical
fiber 33 and inside the second conical entrance 13. A lens 39 is
seated into the second conical entrance 13, such that the optical
epoxy 37 adheres the lens 39 to the optical fiber 33 and the second
conical entrance 13. In a preferred embodiment, the lens 39 is
spherical in shape with a diameter of about 100 to 3,000 um (e.g.,
125 um, 300 um, 500 um, 750 um, 1,250 um 2,500 um), is formed of
sapphire, and has an antireflective coating. However, other types
and sizes of lens may be employed. For example, the lens 39 could
have other shapes such as a barrel, plano-convex or aspherical; the
lens 39 could be formed of other materials like optical glass,
cubic zirconia, quartz, or quartz-like materials; and the lens 39
could be uncoated.
[0061] The index of refraction of the optical fiber 33 is typically
1.46 to 1.49 (e.g., less than approximately 1.5). However, it is
envisioned that the optical fiber could have an index of refraction
which slightly higher, such as an index of refraction which is less
than 1.6. The index of refraction for the lens 39 will be set
greater than 1.5, and usually greater than 1.6. Desirably, the
index of refraction of the lens 39 is greater than the index of
refraction of the optical fiber 33. For example, if the index of
refraction of the optic fiber 33 is less than 1.6, the index of
refraction of the lens 39 is greater than 1.6. As another example,
if the index of refraction of the lens 39 is greater than 1.5, the
index of refraction of the optical fiber 33 is less than 1.5.
[0062] The optical epoxy 37 preferably has optical characteristics
matching or close to the optical characteristics of the optical
fiber 33 and/or the lens 39. More preferably, the optical epoxy 37
has an index of refraction value (e.g. 1.57) which is between the
index of refraction value (e.g. 1.46 to 1.49) of the optical fiber
33 and the index of refraction value (e.g. 1.7) of the lens 39. For
example, the epoxy 37 could have an index of refraction value
between about 1.4 and 1.8.
[0063] The retaining sleeve 21 is slid over the cordage 31 to cover
the junction between the cordage 31 and the ferrule 5. Additional
epoxy or another type of adhesive 41 is inserted into the junction
area where the cordage 31 meets the ferrule 5. The adhesive 41 is
illustrated with dots in FIG. 1 and need not have any particular
optical characteristics. The adhesive 41 may be inserted into this
area using a syringe through the end of the retaining sleeve 21,
which does not possess the ferrule 5. Alternatively, the syringe
may be inserted through a hole 43 in a sidewall of the retaining
sleeve 21. The adhesive 41 adheres to the KEVLAR fibers 35, the end
of the cordage 31, the retaining sleeve 21, the optical fiber 33,
and/or the first end 7 of the ferrule 5. EPOTEC 353ND and HYSOL 151
by Locktite work well.
[0064] Lastly, the technician may use a scope to peer through the
inspection slot 45 to view the status of the epoxy 37 and the
connection of the lens 39 to the optical fiber 33 and the second
end 11 of the ferrule 5. The technician may add epoxy 37 and/or
position the end of the optical fiber 33 a preferred distance from
lens 39 while viewing the gap through inspection slot 45
[0065] FIG. 2 is a top view illustrating approximately one half of
the ferrule 5 adjacent to the second end 11. FIG. 3 is a side view,
similar to FIG. 1 but not in cross section, illustrating
approximately one half of the ferrule 5 adjacent to the second end
11. FIG. 4 is an end view of the second end 11 of the ferrule
5.
[0066] FIG. 5 demonstrates how a first terminus 3-1 may be
connected to an identically constructed second terminus 3-2 to
configure a jumper 51. As can be seen in FIG. 5, a select length of
cordage 31 may be cut, e.g. 3 inches, 6 inches, 30 cm, 500 meters.
The first terminus 3-1 is attached to one end of the cordage 31 and
the second terminus 3-2 is attached to the other end of the cordage
31. In FIG. 5, the first terminus 3-1 and the second terminus 3-2
are illustrated in cross section, whereas the cordage 31 is
illustrated in a side view, without cross section, to simplify the
drawing.
[0067] The jumper 51 can be used to independently replace channels
of a multi-channel connector, as will be described hereinafter. In
so doing, the jumper 51 can minimize repair costs.
[0068] FIG. 5A is a cross sectional view similar to FIG. 1, but
illustrating an alternative design for the terminus 3. In FIG. 5A,
the alternative terminus 3' includes many identical parts as
compared to the terminus 3, and such identical parts are identified
by the same reference numerals. The primary distinction of
alternative terminus 3' is that the second conical entrance 13'
extends further into the ferrule 5, such that the lens 39 is
recessed into the second end 11 of the ferrule 5. Also, the
inspection slot 45' has been extended further back into the ferrule
5.
[0069] In an alternative embodiment depicted in FIG. 5B, retaining
features 17 and 19 have been replaced by a dual purpose retaining
sleeve 77. The retaining sleeve 77 serves the same purpose as the
retaining sleeve 21 in FIG. 5A and also serves the purposes of
providing a connecting feature for interaction with other objects
(e.g., connector envelopes).
[0070] The ferrule 75 has a reduced diameter portion 79 to receive
the retaining sleeve 77. The reduced diameter portion 79 includes a
perimeter groove 81. The retaining sleeve 77 may be attached to the
ferrule 75 by applying a series of crimps, or a continuous crimp,
along a perimeter of the retaining sleeve 77 generally located
beneath arrow 83. The retaining sleeve 77 may also be attached to
the ferrule 75 by epoxy and/or by pressing the two members
together, wherein a frictional attachment occurs due to the size of
the inner diameter of the retaining sleeve 77 being approximately
the same as the outer diameter of the reduced diameter portion 79
of the ferrule 75, e.g., an interference fit.
[0071] For connections to other objects (e.g. connector envelopes),
the retaining sleeve 77 could include a protruding or recessed
feature on its outer surface, such as the depicted cutout 85. The
cutout 85 would allow a technician to insert or inspect epoxy at
the rear of the ferrule 75, if desired. The cutout 85 could also be
engaged by other fixing devices of secondary structures. For
example, a crimp or pin in a secondary structure could protrude
into the cutout 85 to fix the terminus of FIG. 5B to the secondary
structure.
[0072] The recessed nature of the lenses 39 in FIGS. 5A and 5B will
protect the lens 39 in physical contact (PC) type connectors, and
will essentially convert a PC type connector into an expanded beam
connector as will be seen in relation in FIG. 6. In a PC-type
connector, the light carrying optical fiber passes through and
completely to the end of the ferrule or other holding structure.
The end of the ferrule is in physical contact with another ferrule
(or structure for transmitting/receiving light) having a polished
end with an optic fiber terminating in its end. The Applicants have
appreciated drawbacks in the PC connectors of the background
art.
[0073] The PC connector is very susceptible to communication errors
in harsh environments. Since the diameter of the light transmission
path between the ferrules of mating connectors is very small, any
dust or debris in this location will severely attenuate the signal
strength. Also, the aspect of physical contact is very troublesome
when vibrations are present. The vibration leads to wear, scratches
and damage to the optic fiber ends. The wear changes the
performance characteristics of the connector over time. Further,
the wear can lead to misalignments in the connector and signal
transmission failure.
[0074] U.S. Pat. No. 6,074,100 discussed in the background art
section herein addressed one of these drawbacks by recessing the
optical fiber end back from the end surface of the ferrule.
However, the present invention also converts the connector into an
expanded beam connector by virtue of the lens 39, which even
further improves the performance of a PC connector in a harsh
environment, as will be detailed hereinafter. To this end, the
present invention provides expanded beam connectors with physical
dimensions and feature locations (i.e. the envelope of the
connector) to replace standardized PC connectors.
[0075] FIG. 6 illustrates a standard ST type connector envelope
with the expanded beam features of the present invention.
Specifically, the physical contact ferrule assembly of the
background art has been removed. In its place, Applicants have
inserted an expanded beam ferrule assembly 61 (which may be
constructed the same as, or similar to, the ferrule 3' of FIG. 5A
or ferrule 75 FIG. 5B). The expanded beam ferrule assembly 61 may
include the retainer ring 19, as illustrated in FIG. 5A in order to
attach the ferrule assembly 61 to a collar 63 of the ST connector.
Alternatively, the collar 63 may be press fit onto the stainless
steel sleeve 77 of the ferrule assembly of FIG. 5B, or adhered
thereto by epoxy, or by any other fixing manner. Alternatively, the
expanded beam ferrules 5 or 75 may be pressed, or attached by an
epoxy, directly into the collar 63, without any need for retaining
features 17 and 19 and/or any need for a retaining sleeve 21 or
77.
[0076] As seen in FIG. 6, the ferrule assembly 61 has a central
bore through which a light carrying optical fiber 65 passes. A lens
67 is positioned within a conical recess 69 in the face of the
ferrule assembly 61. An index matching epoxy fixes the lens 67 to
the optical fiber 65 and the conical recess 69. The connections
between the optical fiber 65, conical recess 69 and lens 67 may be
inspected via the inspection slot 68.
[0077] As can be seen in FIG. 6, the lens 67 is recessed into the
ferrule assembly 61, via the conical recess 69, by a distance
greater than the diameter of the lens 67. Therefore, the lens 67 is
protected in the end of the ferrule assembly 61, i.e. a planar
object in contact with the end of the ferrule assembly 61 will not
come into physical contact with the lens 67.
[0078] Applicants have discovered that the expanded beam ST
connector has many advantages over the PC ST connector. The lens 67
widens the light path to about three times the diameter of the
optical fiber 65 and larger lens can be employed to widen the light
path even greater than about three times the diameter of the
optical fiber 65. This is particularly advantage in high vibration
environments, which generate dust and debris. For example, with the
connector of U.S. Pat. No. 6,074,100 physical contact exists
between the ferrule and the transmitting/receiving structure. If
vibration causes wear on the interface, the wear can generate dust
within the connector. If a piece of dust or dirt having a cross
sectional area equal to half the end surface area of the optic
fiber 65 were to be in the center of a PC ferrule of the background
art, that piece of dirt could block about 50% of the light passing
through the connector. Most likely, the PC ST connector would fail
under that circumstance. If that same sized piece of dirt were to
be in the center of the expanded beam ferrule assembly 61 of the
present invention, it would block about 11% of the light passing
through the connector. Most likely the expanded beam ST connector
would continue to function.
[0079] Also, in the PC ST connector of the background art, direct
physical contact of the optical fiber at the end of the ferrule is
troublesome. Vibration in the connector leads to wear, scratches
and damage to the optical fiber end. The wear changes the
performance characteristics of the connector over time. The
expanded beam ST connector of the present invention does not suffer
this drawback. The lens 67 does not come into direct contact with
another object. Rather, there is an optimum spacing for the lens 67
from a detector lens or optical fiber. The optimum spacing is
preferably 5 to 100/1000 of an inch to achieve minimum signal
attenuation. However, this spacing will vary depending upon the
material, coatings, size and shape of the lens 67. Having the light
transmitting and receiving features separated by a gap insulates
them from wear concerns and helps to keep the performance
characteristics of the expanded beam ST connector constant over
time.
[0080] Also, the expanded beam ST connector is less susceptible to
unintentional disconnects. In the PC ST connector, if a technician
unintentionally snags the cordage 75 entering the PC ST connector
while working with tools, or a shock wave strikes the connector or
device, the PC ferrule can slightly retract into the connector
envelope against the bias of the spring 73 encircling the collar
63. If the PC ferrule retracts more than 1/2 of a wavelength of the
signal, the signal connection will be lost. In ships, airplanes,
submarines, etc., loss of the signal can be a trigger to reset
computer equipment or to proceed to an emergency program. Either
circumstance can be dangerous.
[0081] In the expanded beam ST connector of the present invention,
physical contact along the light path in the connector is not
required. Rather, a gap is purposefully present. Moreover, due to
the lens 67 the gap may be expanded greatly without loosing the
signal connection through the connector. For example, if the
cordage of the expanded beam ST connector is snagged by a
technician the expanded beam ferrule assembly 61 could be retracted
approximately 1,000 times further into the collar 63, as compared
to the PC ferrule of the PC ST connector, without disconnecting the
signal connection, assuming the collar 63 would even permit such a
retraction length.
[0082] FIG. 7 includes a top view and an end view of an expanded
beam MT type connector, in accordance with the present invention.
The MT type connector is generally block shaped and typically has
dimensions on the order of 3/8''.times.1/8''.times.3/8''. The MT
physical contact (PC) connector of the background art has two to
twelve channels, such as eight channels. If one channel breaks or
is damaged, the entire MT PC connector of the background art is
replaced. Applicants appreciated that this was wasteful.
[0083] Therefore, Applicants have devised an expanded beam MT
connector which has all of the advantages mention above in
connection with expanded beam ferrules over PC ferrules. FIG. 7 is
a top view of the expanded beam MT connector 81, whereas FIG. 7A is
a connector end view of the expanded beam MT connector 81.
[0084] The expanded beam MT connector can have individual channels
repaired by a technician. For instance, an optic fiber extending
from the fiber optic cable to a defective channel within the MT
connector 81 could be cut and a new terminus installed onto the cut
optical fiber on the fiber optic cable side. The defective terminus
within the MT connector 81 could be removed and if sufficient fiber
optic cable length were present, the newly installed terminus could
be plugged into the vacated position in the MT connector 81 where
the defective terminus was removed. If insufficient fiber optic
cable length exists, the repair could be facilitated using a jumper
51, as illustrated in FIG. 5.
[0085] As can be seen in FIG. 7, the expanded beam MT connector 81
has an alignment pin 83 and an alignment hole 85. A top of the MT
connector 81 is open to exposed eight v-grooves 87-1 through 87-8.
Eight termini 89-1 through 89-8 reside in the eight v-grooves 87-1
through 87-8. As best seen in FIG. 7A, the eight termini 89-1
through 89-8 present eight lenses 91-1 through 91-8 at a connection
end of the MT connector 81. The lenses 91-1 through 91-8 are
slightly recessed into the connection end of the MT connector 81 to
protect the lenses 91-1 through 91-8 from wear.
[0086] FIG. 8 is a top view of an alternative expanded beam MT type
connector 81', in accordance with the present invention. FIG. 8A is
a connector end view of the alternative expanded beam MT connector
81'. The alternative expanded beam MT type connector 81' does not
have an open top, but rather includes bores 93-1 through 93-8. The
termini 89-1 through 89-8 are located in the bores 93-1 through
93-8. The lenses 91-1 through 91-8 are slightly recessed into the
connection end of the alternative MT connector 81' to protect the
lenses 91-1 through 91-8 from wear.
[0087] Although FIGS. 7, 7A, 8 and 8A illustrated termini 89-1
through 89-8, it should be appreciated that several advantages of
the present invention could also be obtained by simply fixing the
cordage or optical fiber directly in the v-grooves 87-1 through
87-8 or in the bores 93-1 through 93-8. The cordage or optical
fibers could be fixed by an epoxy. Such a modification would still
have the recessed lenses 91-1 through 91-8 and would still enjoy
the benefits of the improved immunity to dust and debris and the
improved protection from wear; however the ability to replace an
individual channel would be impaired.
[0088] Although FIGS. 6, 7, 7A, 8 and 8A have illustrated ST and MT
type connector envelopes, it should be appreciated that the
expanded beam ferrules of the present invention could be applied to
other types of connector envelopes, such as LC, SC, FC, MU, ROC,
38999 or 29504 type connector envelopes.
[0089] Now with reference to FIGS. 9-16 a terminus 103 in
accordance with a second general embodiment of the present
invention will be described. The terminus 103 can be used as
described above in relation to the terminus 3 (e.g., in connectors,
jumpers, attenuators). The Applicants have discover that forming
the second conical entrance 13 in the second end 11 of the ferrule
5, as depicted in FIG. 1, is often difficult. The dimensions of the
second conical entrance 13 must be precise to have a properly
aligned lens 39, and the common ceramic material of the ferrule 5
is difficult to machine to a high tolerance. Given batches of
machined ferrules 5, which were examined, revealed ferrules 5 with
well-formed second conical entrances 13 intermixed with ferrules 5
having second conical entrances 13, which are out of
specifications. Therefore, each ferrule 5 must be inspected and
out-of-tolerance ferrules 5 must be discarded/recycled.
[0090] Now with reference to FIGS. 9-16, a second embodiment of the
expanded beam terminus 103 will be described. The second embodiment
of the terminus 103 includes one or more of the advantages of the
first embodiment of the terminus 3 described in relation to FIGS.
1-8A and is more easily fabricated to a high tolerance.
[0091] FIG. 9 is a perspective view of a first part 101 of the
terminus 103, in accordance with the second embodiment of the
present invention. The first part 101 includes a ferrule 105. In a
preferred embodiment, the ferrule 105 is a one-piece integral
structure generally cylindrical in shape, made of ceramic (e.g.,
zirconia, glass, alumina), and has an outside diameter of 750 um.
Of course, other shapes, sizes and materials (such as metal,
polymer or composite materials) may be selected for the ferrule
105.
[0092] As best seen in FIG. 12, a first end 107 of the ferrule 105
includes a conical entrance 109. The conical entrance 109 is
generally centered in the first end 107. A second end 111 of the
ferrule 105 is generally flat (i.e., may include a slightly radius
after a final polishing process). The second end 111 of the ferrule
105 may optionally include a beveled edge 110 around its perimeter.
A bore 115 passes through the center of the ferrule 105 from a
center of the first conical entrance 109 to a center of the second
end 111 of the ferrule 105.
[0093] The first part 101 of the terminus 103 also includes a
retaining sleeve 121. The retaining sleeve 121 is generally
cylindrical in shape, made of metal (such as stainless steel), and
has an inner diameter approximately equal to or slightly less than
750 um (i.e., slightly less than the outer diameter of the ferrule
105 to create a pressure fit of the ferrule 105 within the
retaining sleeve 121). Of course, the retaining sleeve 121 could be
made of other materials, such as ceramic, polymer or composite
materials. Also, the retaining sleeve 121 could be differently
shaped and sized, so long as the ferrule 105 could be registered
into the retaining sleeve 121, as illustrated in FIGS. 9-12.
[0094] Now, an assembly of the first part 101 of the terminus 103
to a fiber optic cable or cordage 131 will be described. It is
envisioned that the assembly of the cordage 131 to the first part
101 of the terminus could be performed by a technician in the
field, rather than in a factory. First, the cordage 131 is passed
through the retaining sleeve 121. Next, an outer layer of the
cordage 131 is removed to expose a section of the light carrying
fiber 133 (approximately as long as the ferrule 105) and a short
section of the cable strength members, e.g., KEVLAR fibers 135,
which surround the light carrying optical fiber 133 (as depicted in
FIG. 12).
[0095] The light carrying optical fiber 133 is inserted into the
bore 115 at the first end 107 of the ferrule 105 using the first
conical entrance 109 as a guide. The optical fiber 133 is passed
through the bore 115 to slightly extend out of the second end 111
of the ferrule 105. The optical fiber optical fiber 133 may be
coated with an epoxy prior to being inserted into the bore 115, as
described in conjunction with the prior art of FIG. 18. At the
second end 111 of the ferrule 105, the optical fiber 133 is cut
flush with the second end 111. Then, the optical fiber 133 and the
second end 111 are polished, also in a traditional manner as known
in the art.
[0096] The retaining sleeve 121 is slid over the cordage 131 to
cover the junction between the cordage 131 and the ferrule 105. An
epoxy or another type of adhesive 141 is inserted into the junction
area where the cordage 131 meets the ferrule 105. The adhesive 141
is illustrated with dots in FIG. 12 and need not have any
particular optical characteristics. The adhesive 141 may be
inserted into this area using a syringe through the end of the
retaining sleeve 121, which does not possess the ferrule 105.
Alternatively or additionally, the syringe may be inserted through
an optional hole 143 in a sidewall of the retaining sleeve 121. The
adhesive 141 adheres to the KEVLAR fibers 135, the end of the
cordage 131, the retaining sleeve 121, the optical fiber 133,
and/or the first end 107 of the ferrule 105. EPOTEK 353ND and HYSOL
151 by Locktite work well.
[0097] FIG. 13 is a perspective view of a second part 102 of the
terminus 103, in accordance with the second embodiment of the
present invention. The second part 102 includes a cap sleeve 151.
In a preferred embodiment, the cap sleeve 151 is a one-piece
integral structure in the shape of an open ended tubular cylinder
or an open ended split cylinder (having a split along its sidewall
from a first open end to a second open end which can slightly part
or open to expand the inner diameter of the cap sleeve 151) and has
an inner diameter approximately equal to or slightly greater (e.g.,
about one to two microns) than 750 um (i.e., slightly greater than
the outer diameter of the ferrule 105). In a preferred embodiment,
the cap sleeve 151 is made of ceramic (e.g. zirconia, glass,
alumina), but the cap sleeve 151 could be made of other materials,
such as metal, polymer or composite materials. Also, the cap sleeve
151 could be differently shaped and sized, so long as the ferrule
105 can be registered into the cap sleeve 151, as illustrated in
FIGS. 14-16. In a preferred embodiment, the cap sleeve 151 directly
contacts the ferrule 105 with no intervening structures residing
therebetween.
[0098] The second part 102 of the terminus 103 also includes a lens
139. In a preferred embodiment, the lens 139 is spherical in shape
with a diameter of about 100 to 3,000 um (e.g., 125 um, 300 um, 500
um, 750 um, 1,250 um 2,500 um), is formed of sapphire, and has an
antireflective coating. However, other types and sizes of lens may
be employed. For example, the lens 139 could have other shapes such
as a sphere with a flat surface (See FIG. 15A), a barrel (See FIGS.
15B, 15C and 15D), a plano-convex type or an aspherical type; and
the lens 139 could be formed of other materials like optical glass,
cubic zirconia, quartz or quartz-like materials, or polyetherimide
or similar polymer materials; and the lens 139 could be
uncoated.
[0099] The index of refraction of the optical fiber 133 is
typically 1.46 to 1.49 (e.g., less than approximately 1.5).
However, it is envisioned that the optical fiber 133 could have an
index of refraction which slightly higher, such as an index of
refraction which is less than 1.6. The index of refraction for the
lens 139 will be set greater than 1.5, and usually greater than
1.6. Desirably, the index of refraction of the lens 139 is greater
than the index of refraction of the optical fiber 133. For example,
if the index of refraction of the optic fiber 133 is less than 1.6,
the index of refraction of the lens 139 is greater than 1.6. As
another example, if the index of refraction of the lens 139 is
greater than 1.5, the index of refraction of the optical fiber 133
is less than 1.5.
[0100] The lens 139 is attached within the cap sleeve 151 by an
epoxy 153, as best illustrated in the cross sectional view of FIG.
15. The attachment between the lens 139 and the cap sleeve 151 may
be accomplished in a factory setting, such that the assembled
second part 102 of the terminus 103 could be supplied as a
sub-assembly to the field technicians. By assembling the lens 139
within the cap sleeve 151 in a factory, a very precise location and
firm attachment may be accomplished in a clean, controlled
environment using guides and measuring instruments for
verifications. Alternatively, the lens 139 may be integrally formed
within the cap sleeve 151. In other words, the cap sleeve 151 and
lens 139 may be formed as a unitary piece of an optical glass or
optical grade polymer, such as polycarbonate, with the lens being
molded and/or turned down directly in place within the cap sleeve
151.
[0101] The second part 102 of the terminus 103 would be carried by
a field technician to a job site. After the first part 101 of the
terminus is installed on the end of the optical fiber 133, as
discussed in relation to FIGS. 9-12, the technician would "cap" the
end of the ferrule 105 with the cap sleeve 151. To attach the cap
sleeve 151 to the ferrule 105, an epoxy could be applied to the
outer surfaces of the ferrule 105 and/or the inner surfaces of the
cap sleeve 151 prior to placing the cap sleeve 151 over the second
end 111 of the ferrule 105. A "capped" ferrule 105 would
effectively convert the termination into an expanded beam
termination having all of the benefits and advantages as described
in relation to the first embodiment of the invention (FIGS.
1-8A).
[0102] FIG. 15 is a cross sectional view taken along line XV-XV in
FIG. 14. As seen in FIGS. 14 and 15, the lens 139 slightly
protrudes from an end face 155 of the cap sleeve 151. Also, the end
of the optical fiber 133, which is flushed with the second end 111
of the ferrule 105 directly abuts the lens 139. In such a
configuration, no optical epoxy need reside between the optical
fiber 133 and lens 139 interface. As the lens 139 has a diameter
which is several multiples larger than a diameter of a cylindrical
shape of the optical fiber 133, the surfaces of the facing optical
fiber and spherical lens begin to approximate parallel surfaces.
For example, the spherical lens may have a diameter which is at
least three times greater (and more preferably about four or more
times greater) than a diameter of the optical fiber 133. By making
the lens 139 so large relative to the optical fiber 133, spherical
aberration problems with the lens 139 are reduced. This relative
sizing between the lens 139 and the optical fiber 133 also apply to
the first embodiment of FIG. 1.
[0103] As noted above, the lens 139 may be of a different type or
shape. For example, in the close-up cross sectional view of FIG.
15A, a spherically shaped lens 301 has a flat surface 303 facing to
the second end 111 of the ferrule 105. The flat surface 303 of the
lens 301 would present a parallel surface to the end of the optical
fiber 133. The lens 301 may be attached to the cap sleeve 151 by an
epoxy 153.
[0104] FIG. 15B is a perspective view of a barrel lens 305. The
barrel lens 305 has a generally cylindrical mid-region 307 and
includes a first convex surface 309 on a first end of the generally
cylindrical mid region 307 and a second convex surface 311 on the
opposite, second end of the generally cylindrical mid-region
307.
[0105] As best seen in FIG. 15C, the generally cylindrical
mid-region 307 has a diameter which is approximately equal to, or
slightly less than, an inner diameter of the cap sleeve 151. The
barrel lens 305 may be attached to the cap sleeve 151 by an epoxy
153. As in FIG. 15C, a portion of the barrel lens 305, namely a
portion of the second convex surface 311 protrudes past the end
face 155 of the cap sleeve 151.
[0106] FIG. 15D is a slide view of an alternative barrel lens 313.
The alternative barrel lens 313 has an extended length, generally
cylindrical mid region 315 located between the first convex surface
309 and the second convex surface 311. The extended length of the
generally cylindrical mid region 315 can provide a more stable
mounting of the alternative barrel lens 313 within the cap sleeve
151. As with the previous embodiments, the lens 301, 305 and 313
could be formed of sapphire or other materials like optical glass,
cubic zirconia, quartz or quartz-like materials, or polyetherimide
or similar polymer materials, and may include an antireflective
coating or be uncoated.
[0107] Although FIG. 15 illustrates the end of the optical fiber
133, which is flushed with the second end 111 of the ferrule 105,
directly abutting the lens 139, it may be desirable to space the
end of the optical fiber 133 from the lens 139. The lens 139 will
have a focal point determined by factors such as the index of
refraction of the lens and the shape of the lens. In certain
embodiments, where the focal point of the lens 139 is spaced from
the outer physical edge of the lens 139, it may be desirable to
locate the end of the optical fiber 133 at the focal point of the
lens 139, i.e., a certain distance from the lens 139. The gap
between the end of the optical fiber 133 and the lens 139 may be an
air gap or filled by optical epoxy, as more fully explained in
relation to FIG. 16 below.
[0108] FIG. 16 shows an alternative cap sleeve 151'. The
alternative cap sleeve 151' is slightly longer that the cap sleeve
151 of FIG. 15. By this arrangement, the lens 139 is slightly
recessed into the cap sleeve 151' and does not protrude past the
end face 155 of the cap sleeve 151'. By this arrangement, the lens
139 of the modified terminus 103' will not come into physical
contact with a structure abutting the end face 155. Hence, the
modified terminus 103' has lens 139 recessed from end face 155
creating a fixed minimum lens separation to the mating
connector.
[0109] FIG. 16 also illustrates that the lens 139 may be slightly
distanced from the end of the optical fiber 133. An optical epoxy
137 adheres the lens 139 to the end of the optical fiber 133. The
optical epoxy 37 would be applied by the field technician either
directly to the end of the ferrule 105 and/or to the lens 139 using
a syringe prior to inserting the ferrule 105, such that light
exiting the termination end of the optical fiber 133 passes through
the optical epoxy 137 prior to entering into the lens 139. Also, an
inspection slot or small hole 157 could be provided in a side wall
of the cap sleeve 151' proximate the lens 139, which affords a view
of an area between the lens 139 and the second end 111 of the
ferrule 105 when the cap sleeve 151 is attached to the ferrule 105.
The hole 157 would also permit the optical epoxy 137 to be applied
using a syringe and the hole 157 would function as a vent.
[0110] Also, if the small hole 157 is provided, the technician may
use a scope to peer through the hole 157 to view the status of the
optical epoxy 137 and the connection of the lens 139 to the optical
fiber 133 and the second end 111 of the ferrule 105. The technician
may add optical epoxy 137 and/or position the end of the optical
fiber 133 a preferred distance from lens 139 while viewing the gap
through hole 157. Of course the hole 157 and optical epoxy 137
could be used in the embodiment depicted in FIG. 15 where the lens
139 slightly protrudes from the end face 155 of the cap sleeve
151.
[0111] The optical epoxy 137 will be the same or similar to the
optical epoxy 37 described earlier. Namely, the optical epoxy could
have optical characteristics matching or close to the optical
characteristics of the optical fiber 133 or the lens 139, or
between the optical characteristics of the optical fiber 133 and
the lens 139. For example, The optical epoxy 137 may have an index
of refraction value (e.g. 1.57) which is between the index of
refraction value (e.g. 1.46 to 1.49) of the optical fiber 133 and
the index of refraction value (e.g. 1.7) of the lens 139. For
example, the epoxy 37 could have an index of refraction value
between about 1.4 and 1.8.
[0112] In the embodiments of FIGS. 14-16, it can be seen that the
cap sleeve 151/151' does not completely seat against the retaining
sleeve 121. A gap 159 circumscribes the area between the cap sleeve
151/151' and the retaining sleeve 121. This gap 159 can serve the
purpose of a retaining feature, providing an anchoring structure
for interaction with other objects (e.g., connector envelopes).
Like the cutout 85 in the embodiment of FIG. 5B. The gap 159 could
be engaged by other fixing devices of secondary structures. For
example, a crimp in a secondary structure could protrude into the
gap 159 to fix the terminus 103/103' of FIGS. 14-16 to the
secondary structure.
[0113] The invention being thus described, it will be obvious that
the same may be varied in many ways. Such variations are not to be
regarded as a departure from the spirit and scope of the invention,
and all such modifications as would be obvious to one skilled in
the art are to be included within the scope of the following
claims.
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