U.S. patent application number 16/372374 was filed with the patent office on 2020-01-02 for hermetic optical fiber alignment assembly having integrated optical element.
The applicant listed for this patent is NANOPRECISION PRODUCTS, INC.. Invention is credited to Michael K. BARNOSKI, Shuhe LI, Robert Ryan VALLANCE.
Application Number | 20200003973 16/372374 |
Document ID | / |
Family ID | 49512578 |
Filed Date | 2020-01-02 |
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United States Patent
Application |
20200003973 |
Kind Code |
A1 |
LI; Shuhe ; et al. |
January 2, 2020 |
HERMETIC OPTICAL FIBER ALIGNMENT ASSEMBLY HAVING INTEGRATED OPTICAL
ELEMENT
Abstract
A hermetic optical fiber alignment assembly includes a ferrule
portion having a plurality of grooves receiving the end sections of
optical fibers, wherein the grooves define the location and
orientation of the end sections with respect to the ferrule
portion. The assembly includes an integrated optical element for
coupling the input/output of an optical fiber to the
opto-electronic devices in the opto-electronic module. The optical
element can be in the form of a structured reflective surface. The
end of the optical fiber is at a defined distance to and aligned
with the structured reflective surface. The structured reflective
surfaces and the fiber alignment grooves can be formed by
stamping.
Inventors: |
LI; Shuhe; (Pasadena,
CA) ; VALLANCE; Robert Ryan; (Newbury Park, CA)
; BARNOSKI; Michael K.; (Pacific Palisades, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
NANOPRECISION PRODUCTS, INC. |
Camarillo |
CA |
US |
|
|
Family ID: |
49512578 |
Appl. No.: |
16/372374 |
Filed: |
April 1, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13861273 |
Apr 11, 2013 |
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16372374 |
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13786448 |
Mar 5, 2013 |
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13861273 |
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61623027 |
Apr 11, 2012 |
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61699125 |
Sep 10, 2012 |
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61606885 |
Mar 5, 2012 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G02B 6/4249 20130101;
G02B 6/4253 20130101; G02B 6/3885 20130101; G02B 6/4214 20130101;
G02B 6/3839 20130101; G02B 6/4295 20130101; Y10T 29/49 20150115;
G02B 6/3833 20130101; G02B 6/3877 20130101; G02B 6/4219 20130101;
G02B 6/4263 20130101; G02B 6/428 20130101; G02B 6/4292 20130101;
G02B 6/4248 20130101; G02B 6/3838 20130101; G02B 6/4246
20130101 |
International
Class: |
G02B 6/42 20060101
G02B006/42; G02B 6/38 20060101 G02B006/38 |
Claims
1. A hermetic optical fiber alignment assembly, comprising: a first
ferrule portion having a first surface defining at least a groove
receiving at least an end section of an optical fiber, wherein
groove defines the location and orientation of the end section with
respect to the first ferrule portion; a second ferrule portion
having a second surface facing the first surface of the first
ferrule, wherein the first ferrule portion is hermetically attached
to the second ferrule portion with the first surface against the
second surface, wherein the first ferrule includes an extended
portion beyond an edge of the second ferrule portion, on which the
groove extends and terminates at an optical element located beyond
the edge of the second ferrule portion, wherein an end face of the
optical fiber is located at a predetermined distance from the
optical element along the axis of the optical fiber, and wherein
the groove accurately aligns the optical fiber with respect to the
optical element, so that output light from the optical fiber can be
directed by the optical element to outside the ferrule or input
light from outside the ferrule incident at the optical element can
be directed towards the optical fiber.
Description
PRIORITY CLAIM
[0001] This application is a continuation of U.S. patent
application Ser. No. 13/861,273 filed on Apr. 11, 2013, which (a)
claims the priority of U.S. Provisional Patent Application No.
61/623,027 filed on Apr. 11, 2012; (b) claims the priority of U.S.
Provisional Patent Application No. 61/699,125 filed on Sep. 10,
2012; (c) is a continuation-in-part of U.S. patent application Ser.
No. 13/786,448 filed on Mar. 5, 2013, which claims the priority of
U.S. Provisional Patent Application No. 61/606,885 filed on Mar. 5,
2012. These applications are fully incorporated by reference as if
fully set forth herein. All publications noted below are fully
incorporated by reference as if fully set forth herein.
BACKGROUND OF THE INVENTION
Field of the Invention
[0002] The present invention relates to optical fiber ferrule
structures, in particular a hermetic optical fiber alignment
assembly including a ferrule for aligning optical fibers.
Description of Related Art
[0003] Given the increasing bandwidth requirements for modern day
data transmission (e.g., for high definition video data), fiber
optic signal transmissions have become ubiquitous for communicating
data. Optical signals are transmitted over optical fibers, through
a network of optical fibers and associated connectors and switches.
The optical fibers demonstrate a significantly higher bandwidth
data transmission capacity and lower signal losses compared to
copper wires for a given physical size/space.
[0004] In fiber optic signal transmission, conversions between
optical signals and electrical signals take place beyond the
terminating end of the optical fiber. Specifically, at the output
end of an optical fiber, light from the optical fiber is detected
by a transducing receiver and converted into an electrical signal
for further data processing downstream (i.e., optical-to-electrical
conversion). At the input end of the optical fiber, electrical
signals are converted into light to be input into the optical fiber
by a transducing transmitter (i.e., electrical-to-optical
conversion).
[0005] The opto-electronic devices (receiver and transmitter and
associated optical elements and electronic hardware) are contained
in an opto-electronic module or package. The optical fiber is
introduced from outside the housing of the opto-electronic module,
through an opening provided in the housing wall. The end of the
optical fiber is optically coupled to the opto-electronic devices
held within the housing. A feedthrough element supports the portion
of the optical fiber through the wall opening. For a variety of
applications, it is desirable to hermetically seal the
opto-electronic devices within the housing of the opto-electronic
module, to protect the components from corrosive media, moisture
and the like. Since the package of the opto-electronic module must
be hermetically sealed as whole, the feedthrough element must be
hermetically sealed, so that the electro-optic components within
the opto-electronic module housing are reliably and continuously
protected from the environment.
[0006] Heretofore, hermetic feedthrough is in the form of a
cylindrical sleeve defining a large clearance through which a
section of the optical fiber passes. The optical fiber extends
beyond the sleeve into the opto-electronic module. The end of the
optical fiber is terminated in a ferrule (separate from the sleeve)
that is aligned with the opto-electronic devices provided therein.
A sealing material such as epoxy is applied to seal the clearance
space between the optical fiber and inside wall of the sleeve. The
sleeve is inserted into the opening in the opto-electronic module
housing, and the opening is sealed, typically by soldering the
exterior wall of the sleeve to the housing. The outside wall of the
sleeve may be gold plated to facilitate soldering and improve
corrosion resistance.
[0007] Given the large clearance between the sleeve and the optical
fiber and the use of epoxy to seal such clearance (i.e., a layer of
epoxy between the external fiber wall and the inside wall of the
sleeve), the sleeve does not support the optical fiber with any
positional alignment with respect to the sleeve. Given the sealing
material provides stress and strain relief for the section of
optical fiber held therein, the brittle fiber does not easily break
during handling. The sleeve essentially functions as a grommet or
conduit that is sealed to the opto-electronic module housing and
that passes through the optical fiber in a hermetic seal within the
sleeve. As noted below, the end of the optical fiber needs to be
aligned to the opto-electronic devices to within acceptable
tolerances by means of a ferrule.
[0008] To optically couple the input/output of the optical fiber to
the opto-electronic devices in the opto-electronic module, optical
elements such as lenses and mirrors are required to collimate
and/or focus light from a light source (e.g., a laser) into the
input end of the optical fiber, and to collimate and/or focus light
from the output end of the optical fiber to the receiver. To
achieve acceptable signal levels, the end of the optical fiber must
be precisely aligned at high tolerance to the transmitters and
receivers, so the optical fiber are precisely aligned to the
optical elements supported with respect to the transmitters and
receivers. In the past, given the internal optical elements and
structures needed to achieve the required optical alignments at
acceptable tolerance, coupling structures including a connection
port is provided within the hermetically sealed opto-electronic
module housing to which a ferrule terminating the end of the
optical fiber is coupled. The transmitters and receivers and
associated optical elements and connection structures are therefore
generally bulky, which take up significant space, thereby making
them not suitable for use in smaller electronic devices.
Heretofore, opto-electronic modules containing transmitters and
receivers are generally quite expensive and comparatively large in
size for a given port count. Given optical fibers are brittle, and
must be handled with care during and after physical connection to
the coupling structure within the opto-electronic module and to
avoid breakage at the feedthrough sleeve. In the event of breakage
of the optical fiber, it has been the industry practice to replace
the entire opto-electronic module to which the hermetic optical
fiber feedthrough is soldered. The connection and optical alignment
of the optical fibers with respect to the transmitters and
receivers must be assembled and the components must be fabricated
with sub-micron precision, and should be able to be economical
produced in a fully automated, high-speed process.
[0009] The above noted drawbacks of existing fiber optic data
transmission are exacerbated in multi-channel fiber
transmission.
[0010] OZ Optics Ltd produces multi-fiber hermetically sealable
patchcord with glass solder having multiple optical fibers passing
through a sleeve, with the optical fibers extending beyond the
sleeve, with the ends of the optical fibers held in an alignment
ferrule separate from the sleeve. OZ Optics Ltd further produces a
multi-fiber hermetically sealable patchcord with metal solder, in
which the optical fibers are coated with a metal (metalized
fibers). The optical fibers are terminated with a silicon ferrule
that is supported within a sleeve, which is a component separate
from the ferrule. The outside wall of the sleeve is gold plated for
sealing to an opto-electronic module housing. However, these
multi-fiber hermetic feedthrough configurations do not appear to
resolve the drawbacks of the prior art noted above, and introduce
additional complexity and cost at least from a manufacturability
perspective.
[0011] What is needed is an improved hermetic optical fiber
alignment assembly, which improves optical alignment,
manufacturability, ease of use, functionality and reliability at
reduced costs.
SUMMARY OF THE INVENTION
[0012] The present invention provides an improved hermetic optical
fiber alignment assembly, which improves optical alignment,
manufacturability, ease of use, functionality and reliability at
reduced costs, thereby overcoming many of the drawbacks of the
prior art structures.
[0013] In one aspect, the present invention provides a hermetic
optical fiber alignment assembly, comprising: a first ferrule
portion having a first surface provided with a plurality of grooves
receiving at least the end sections of a plurality of optical
fibers, wherein the grooves define the location and orientation of
the end sections with respect to the first ferrule portion; a
second ferrule portion having a second surface facing the first
surface of the first ferrule, wherein the first ferrule portion is
attached to the second ferrule portion with the first surface
against the second surface, wherein a cavity is defined between the
first ferrule portion and the second ferrule portion, wherein the
cavity is wider than the grooves, and wherein a suspended section
of each optical fiber is suspended in the cavity, and wherein the
cavity is sealed with a sealant. The sealant extends around the
suspended sections of the optical fibers within the cavity. At
least one the first surface of the first ferrule portion is
provided with a well defining a first pocket in the first ferrule
portion, wherein the first pocket and the second ferrule section
together define the cavity. An aperture is provided in at least one
of the first ferrule portion and the second ferrule portion,
exposing the cavity, wherein the sealant is feed through the
aperture.
[0014] In another aspect of the present invention, the hermetic
optical fiber alignment assembly provides optical alignment and a
hermetic feedthrough for an opto-electronic module. In a further
aspect of the present invention, the hermetic optical fiber
alignment assembly provides alignment and a terminal for access to
an opto-electronic module.
[0015] In yet another aspect of the present invention, an improved
hermetic optical fiber alignment assembly includes an integrated
optical element for coupling the input/output of an optical fiber
to the opto-electronic devices in the opto-electronic module. In
one embodiment, the integrated optical element comprises a
reflective element that is stamped with the alignment groove for
the optical fiber.
[0016] In one embodiment, the hermetic optical fiber alignment
assembly, comprises a first ferrule portion defining an optical
element and an optical fiber retention structure (e.g., an
alignment groove having an open structure) such that an end face of
the optical fiber is located at a predetermined distance from the
optical element along the axis of the optical fiber, wherein an end
face of the optical fiber is located at a predetermined distance
from the optical element along the axis of the optical fiber, and
wherein the optical fiber retention structure accurately aligns the
optical fiber with respect to the optical element, so that output
light from the optical fiber can be directed by the optical element
to outside the first ferrule portion or input light from outside
the first ferrule portion incident at the optical element can be
reflected towards the optical fiber; and a second ferrule portion
hermetically attached to the second ferrule portion, wherein the
first ferrule includes an extended portion beyond an edge of the
second ferrule portion, on which the optical element is located
beyond the edge of the second ferrule portion.
[0017] In another embodiment, the hermetic optical fiber alignment
assembly comprises a first ferrule portion having a first surface
defining at least a groove receiving at least an end section of an
optical fiber, wherein groove defines the location and orientation
of the end section with respect to the first ferrule portion; a
second ferrule portion having a second surface facing the first
surface of the first ferrule, wherein the first ferrule portion is
hermetically attached to the second ferrule portion with the first
surface against the second surface, wherein the first ferrule
includes an extended portion beyond an edge of the second ferrule
portion, on which the groove extends and terminates at an optical
element located beyond the edge of the second ferrule portion,
wherein an end face of the optical fiber is located at a
predetermined distance from the optical element along the axis of
the optical fiber, and wherein the groove accurately aligns the
optical fiber with respect to the optical element, so that output
light from the optical fiber can be directed by the optical element
to outside the ferrule or input light from outside the ferrule
incident at the optical element can be directed towards the optical
fiber.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] For a fuller understanding of the nature and advantages of
the invention, as well as the preferred mode of use, reference
should be made to the following detailed description read in
conjunction with the accompanying drawings. In the following
drawings, like reference numerals designate like or similar parts
throughout the drawings.
[0019] FIG. 1 is a schematic perspective view of an opto-electronic
module housing, to which hermetic optical fiber assemblies are
hermetically sealed, in accordance with one embodiment of the
present invention.
[0020] FIG. 2 is a schematic perspective view illustrating an
optical jumper patchcord having hermetic optical fiber assemblies,
in accordance with one embodiment of the present invention.
[0021] FIG. 3 is a schematic diagram illustrating the optical
jumper patchcord in FIG. 2 with the hermetic optical fiber assembly
hermetically sealed to an opto-electronic module housing, in
accordance with one embodiment of the present invention.
[0022] FIGS. 4A to 4C are perspective views of the hermetic optical
fiber assembly, in accordance with one embodiment of the present
invention.
[0023] FIGS. 5A to 5C are plan views of the hermetic optical fiber
assembly in FIG. 4; FIG. 5D illustrates an alternate
embodiment.
[0024] FIG. 6 is an exploded perspective view of the hermetic
optical fiber assembly in FIG. 4, in accordance with one embodiment
of the present invention.
[0025] FIGS. 7A to 7E are plan views of the cover of the hermetic
optical fiber assembly.
[0026] FIGS. 8A to 8E are plan views of the ferrule of the hermetic
optical fiber assembly.
[0027] FIGS. 9A to 9E are sectional views taken along lines 9A-9A
to 9E-9E in FIG. 5A.
[0028] FIGS. 10A and 10B are perspective views of a light directing
element at the exit end of the optical fibers in the hermetic
optical fiber assembly, in accordance with one embodiment of the
present invention; FIG. 10C is a sectional view taken along line
10C-10C in FIG. 10B.
[0029] FIG. 11 is a schematic perspective view of an
opto-electronic module housing, to which hermetic optical fiber
assemblies are hermetically sealed, in accordance with another
embodiment of the present invention.
[0030] FIG. 12 is a photographic sectional view of a prototype of
the hermetic optical fiber assembly.
[0031] FIG. 13 is a sectional view showing addition detail of the
mounting of the hermetic optical fiber assembly to the
opto-electronic module housing, in accordance with another
embodiment of the present invention.
[0032] FIG. 14 is a schematic perspective view of a hermetic
optical fiber alignment assembly having an integral optical
element, in accordance with one embodiment of the present
invention.
[0033] FIG. 15 is a schematic perspective view of the underside of
the hermetic optical fiber alignment assembly of FIG. 14.
[0034] FIG. 16 is an enlarged perspective view of the extended
portion of the ferrule, in accordance with one embodiment of the
present invention.
[0035] FIG. 17A is a sectional view of the fiber alignment groove
along a longitudinal axis of the optical fiber; FIG. 17B is a
perspective sectional view thereof.
[0036] FIG. 18 is a sectional view illustrating reflection of light
between optical fiber and an opto-electronic device, in accordance
with one embodiment of the present invention.
[0037] FIG. 19 is a sectional view illustrating reflection of light
between optical fiber and an opto-electronic device, in accordance
with another embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0038] This invention is described below in reference to various
embodiments with reference to the figures. While this invention is
described in terms of the best mode for achieving this invention's
objectives, it will be appreciated by those skilled in the art that
variations may be accomplished in view of these teachings without
deviating from the spirit or scope of the invention.
[0039] The present invention provides an improved hermetic optical
fiber assembly, which improves optical alignment,
manufacturability, ease of use, functionality and reliability at
reduced costs, thereby overcoming many of the drawbacks of the
prior art structures.
[0040] FIG. 1 is a schematic diagram of an opto-electronic module
12, to which hermetic optical fiber assemblies 10 are hermetically
sealed, in accordance with one embodiment of the present invention.
The opto-electronic module 12 includes a housing 14, which includes
a base 16 and a cover hermetically sealed to the housing,
protecting the interior of the housing from the environment
external of the housing. For simplicity, the cover of the
opto-electronic module 12 is omitted in FIG. 1. Enclosed within
chambers in the housing are opto-electronic devices 17 and 18
(e.g., transmitter and receiver and associated electronics and/or
optical elements (not specifically shown in FIG. 1, but
schematically shown in FIG. 3). The electronics within the
opto-electronic module 12 are electrically coupled to an external
circuit board 20 via flexible electrical connection pins 19.
[0041] In the illustrated embodiment, the housing base 16 includes
two openings 21 and 22 through which the hermetic optical fiber
assemblies 10 are inserted. In accordance with one aspect of the
present invention, each hermetic optical fiber assembly 10 serves
as a hermetic feedthrough for optical fibers 24 in a fiber ribbon
23. In the illustrated embodiment, there are four optical fibers 24
in the fiber ribbon 23. The hermetic optical fiber assembly 10 also
serves as a ferrule, which supports the ends (i.e., a section or
"end section") of the optical fibers 24 in a fixed position with
respect to each other and with respect to the external surfaces of
the hermetic optical fiber assembly 10. As will be elaborated
further below, once the hermetic optical fiber assembly 10 is fixed
attached to the housing 14 (e.g., by soldering at the opening (21,
22) in base 16), the ends of the optical fibers 24 would be fixed
in position (i.e., precisely aligned) with respect to the
opto-electronic devices (17, 18) in the housing 14.
[0042] FIG. 2 is a schematic diagram illustrating an optical jumper
patchcord 30 having hermetic optical fiber assemblies 10, in
accordance with one embodiment of the present invention. FIG. 3 is
a schematic diagram illustrating the optical jumper patchcord 30
with the hermetic optical fiber assemblies 10 hermetically sealed
to an opto-electronic module housing, in accordance with one
embodiment of the present invention. In the illustrated embodiment,
the optical jumper patchcord 30 includes two fiber ribbons 23, each
terminating at one end with a hermetic fiber optic assembly 10, and
commonly terminating at another end with a connector 25 for
coupling to a fiber network. The connector 25 and the
opto-electronic module 12 may be part of an opto-electronic
peripheral board, comprising a circuit board (not shown) that
supports the opto-electronic module 12 and the connector 25 at an
edge of the circuit board. In which case, the optical jumper
patchcord 30 serves as a short optical fiber connection from the
opto-electronic module 12 to a built-in terminal (i.e., the
connector 25) of the opto-electronic peripheral board for external
connection to the fiber network or backplane printed circuit
board.
[0043] FIGS. 4 to 9 illustrate the detail structures of the
hermetic optical fiber assembly 10, in accordance with one
embodiment of the present invention. The hermetic optical fiber
assembly 10 is essentially a ferrule assembly, having parallel open
grooves provided therein for aligning the ends of the optical
fibers 24.
[0044] FIGS. 4A to 4C are perspective views of the hermetic optical
fiber assembly 10. FIGS. 5A to 5C are plan views of the hermetic
optical fiber assembly 10. FIG. 6 is an exploded perspective view
of the hermetic optical fiber assembly 10. FIGS. 9A to 9E are
sectional views taken along lines 9A-9A to 9E-9E in FIG. 5A. In the
illustrated embodiment, the ferrule assembly 10 comprises two
ferrule portions, of which a first ferrule portion (hereinafter
referred to as a ferrule 40) is provided with optical fiber
alignment grooves 34 and a second ferrule portion (hereinafter
referred to as a cover 42) is not provided with any alignment
grooves. The ferrule portions each have a generally planar
structure (as compared to a tube or sleeve).
[0045] FIGS. 7A to 7E are plan views of the cover 42 of the
hermetic optical fiber assembly 10. Referring to FIG. 7A, the
underside 38 of the cover 42 (the side facing the ferrule 40) is
provided with a shallow well forming a pocket 44 near the center
and a cutout 45 at one longitudinal end of the cover 42. Chamfers
46 are provided on the longitudinal edges.
[0046] FIGS. 8A to 8E are plan views of the ferrule 40 of the
hermetic optical fiber assembly 10. Referring to FIG. 8A, the
underside 39 of the ferrule 40 (the side facing the cover 42) is
provided with a shallow well forming a pocket 54 near the center
and a cutout 55 at one longitudinal end of the ferrule 40, matching
the pocket 44 and cutout 45. Parallel longitudinal grooves 34 in a
horizontal plane parallel to the underside 39 are provided between
the end face 56 and the pocket 54. Additional parallel longitudinal
grooves 35 in a horizontal plane parallel to the underside 39 are
provided between the pocket 54 and cutout 55. Referring also to
FIG. 9E, the grooves 34 and 35 are sized to receive the terminating
end sections of each optical fiber 24 (i.e., a short section of
each optical fiber bear an end, in its bare state exposing the
cladding layer, with protective buffer layer and jacket removed).
Specifically, the grooves 34 are precisely sized to precisely
position the ends of optical fibers 24 in relation to one another
and the external surfaces of the ferrule 40. Upon attaching the
hermetic optical fiber assembly 10 to the housing 14 (e.g., by
soldering at the opening (21, 22) in base 16), the ends of the
optical fibers 24 would be fixed in position (i.e., precisely
aligned) with respect to the opto-electronic devices (17, 18) in
the housing 14.
[0047] As more clearly shown in FIG. 9E, when the cover 42 and the
ferrule 40 are mated together with the underside 38 of cover 42 and
underside 39 of ferrule 40 against each other, the pockets 44 and
45 together define a cavity 48 through which a section of each
optical fiber 24 is suspended (i.e., not touching the ferrule 40
and the cover 42. The ferrule 40 is provided with an aperture 41,
through which sealant can be feed into the cavity 48. Referring
also to FIG. 9B, the width of the aperture 41 is substantially
wider than the diameter of an optical fiber 24, and extends across
the ferrule to expose all the optical fibers 24 arranged in
parallel (see FIG. 4C; i.e., the width of the aperture 41 is wider
than all the grooves 34 combined in the plane of the ferrule 40).
Further, the cutouts 45 and 55 together form a pocket 49 that
receives a strain relief 43, which supports the fiber ribbon 24
(including protective layers over the bare optical fibers 24) at
the other end of the assembly 10.
[0048] Referring to FIGS. 8D and 9A, the walls of the grooves 34
define a generally U-shaped cross-section. The depth of each groove
34 is sized to completely retain an optical fiber without
protruding above the groove 34, with the top of the optical fiber
substantially in line with the top of the groove (i.e., at
substantially the same level as the surface of the underside 39).
When the cover 42 and the ferrule 40 are mated together with the
underside 38 of cover 42 and underside 39 of ferrule 40 against
each other, the underside 48 of cover 42 just touches the top wall
of the optical fibers as it covers over the grooves 34, thus
retaining the optical fibers 24 in the grooves 34.
[0049] The grooves 34 are structured to securely retain the optical
fibers 24 (bare section with cladding exposed, without protective
buffer and jacket layers) by clamping the optical fibers 24, e.g.,
by a mechanical or interference fit (or press fit). For example,
the width of the grooves 34 may be sized slightly smaller than the
diameter of the optical fibers 24, so that the optical fibers 24
are snuggly held in the grooves 34 by an interference fit. The
interference fit assures that the optical fibers 24 is clamped in
place and consequently the position and orientation of the ends of
the optical fibers 24 are set by the location and longitudinal axis
of the grooves 34. In the illustrated embodiment, the grooves 34
has a U-shaped cross-section that snuggly receive the bare optical
fibers 24 (i.e., with the cladding exposed, without the protective
buffer and jacket layers). The sidewalls of the groove 34 are
substantially parallel, wherein the opening of the grooves may be
slightly narrower than the parallel spacing between the sidewalls
(i.e., with a slight C-shaped cross-section) to provide additional
mechanical or interference fit for the optical fibers 24. Further
details of the open groove structure can be found in copending U.S.
patent application Ser. No. 13/440,970 filed on Apr. 5, 2012, which
is fully incorporated by reference herein. The ferrule 40 having
the grooves 34 is effectively a one-piece open ferrule supporting
the optical fibers 24 with their ends in precise location and
alignment with respect to each other and to the external geometry
of the ferrule 40.
[0050] The grooves 34 may be provided with a rounded bottom in
cross-section (see, FIG. 9A), which would conformally contact as
much as half the cylindrical wall (i.e., semi-circular cylindrical
wall) of the optical fibers. In any event, the wall of the optical
fibers 24 would come into contact (e.g., compressive contact) with
at least the side walls of the grooves 34, with at least the
lateral sides of the optical fibers in tight contact (e.g.,
substantially tangential contact in cross-section) with the side
walls of the grooves 34. Such lateral contact between the optical
fibers and adjacent sidewalls of the grooves 34 ensures a geometry
that defines the necessary horizontal alignment positioning/spacing
of the optical fibers 24 with respect to each other and with
respect to at least the lateral sides of the ferrule 40. The
precise sizing of the depth of the grooves 34 in the ferrule 40
ensures a geometry in reference to the cover 42 that defines the
necessary vertical alignment positioning of the optical fibers 24
with respect to at least the external surface (top surface opposite
to the underside 39) of the ferrule 40.
[0051] Concerning the grooves 35 for retaining the section of the
optical fibers 24 further away from the ends of the optical fibers
24 on the other side of the cavity 48, they may have similar
geometries and/or design considerations as the grooves 34. However,
it is noted that for purpose of optical alignment of the optical
fibers, it is only necessary to provide alignment grooves 34 having
tight tolerance for supporting the terminating end section of the
optical fibers 24. The grooves 35 provided nearer to the strain
relief 43 need not have as strict a tolerance compared to that of
the grooves 34, as the tolerance of the grooves would have no
bearing on the optical alignment of the ends of the optical fiber
24 with respect to an external optical component.
[0052] The hermetic sealing of the assembly 10 can be implemented
by the following procedure, in accordance with one embodiment of
the present invention. With the protective buffer and jacket layers
removed at the end section, the optical fibers 24 is positioned
into the grooves 34 and 35 in the ferrule 40. The cover 42 is mated
against the ferrule (e.g., by an external clamping fixture) in the
configuration illustrated generally by FIG. 9E. The cover 42 and
ferrule 40 are soldered together using gold-tin solder. The chamfer
46 provides some clearance to allow bleeding of excess solder. It
is noted that the chamfer 46 is shown not to extend along the
entire length of the cover 42, to reduce potential clearance to
facilitate soldering between the assembly 10 and the module housing
14.
[0053] Referring also to FIG. 13, a sealant 37 such as glass solder
(or other sealant suitable for hermetic sealing) is feed through
the aperture 41 in the ferrule 40 as vacuum is applied to the
pocket 49, thus drawing glass solder to fill the cavity 48 and
available spaces/clearance between the optical fibers 23, the
grooves 35 and the cover 42, given the grooves are generally
U-shaped in cross-section. (See FIG. 13). Some of the glass solder
also flows to fill available spaces between the optical fibers,
alignment grooves 34 and the cover 42. It is not necessary to draw
glass solder completely through the grooves 34 or 35, as long as
there is sufficient sealant drawn to a sufficient distance to plug
available spaces at least at a region near the entry from the
cavity into the respective grooves. Given the pockets 44 and 54
have depths deeper than the depths of the grooves 34 and 35, the
sealant wraps around the sections of the optical fiber 24 suspended
in the cavity 48. The sealant essentially forms a hermetic plug in
the cavity 48, restricting leakage through the assembly 10. The
structure of the assembly 10 can be hermetically sealed without
requiring any external sleeve, beyond the two ferrule portions
(ferrule 40 and cover 42 in the above described embodiment). The
structure of the hermetic assembly is thus very simple, which
provides an effective hermetic seal.
[0054] It is noted that given the tight contact between the wall of
the optical fibers and the walls of at least the grooves 34, the
sealant does not come between the contact surfaces between the
optical fibers 24, the cover 42 and the walls of groove 34 which
were present prior to applying the sealant. It is intended that the
sealant plugs available spaces and/or clearance between the optical
fibers 24, grooves 34 and cover 42, but do not form an intermediate
layer between the optical fibers and the groove walls at the
contact points prior to applying the sealant, which could otherwise
affect the alignment of the optical fibers by the grooves 34.
[0055] After sealing with the glass solder, an epoxy material is
applied into the pocket 49 to form the strain relief 43. The
exposed ends of the optical fiber 24 may be polished to be
substantially coplanar with the end face 56 of the ferrule 40 to
finish the hermetic assembly 10. The ends of the fibers 24 may
protrude slightly (by at most a few microns) beyond the end face 56
of the ferrule 40 but do not extend appreciably beyond the end face
56 because there is no protective buffer and jacket layers at the
respective ends of the optical fibers 24. To facilitate soldering
of the assembly to the module housing 14 and to improve corrosion
resistance, the surfaces of the cover 42 and/or the ferrule 40 may
be gold plated.
[0056] According to one aspect of the present invention, the
ferrule 40 and/or the cover 42 may be formed by precision stamping
a metal material. In one embodiment, the metal material may be
chosen to have high stiffness (e.g., stainless steel), chemical
inertness (e.g., titanium), high temperature stability (nickel
alloy), low thermal expansion (e.g., Invar), or to match thermal
expansion to other materials (e.g., Kovar for matching glass).
Alternatively, the material may be silicon, a hard plastic or other
hard polymeric material.
[0057] The above disclosed open structure of the ferrule 40 and
cover 42 lends themself to mass production processes such as
stamping, which are low cost, high throughput processes. A
precision stamping process and apparatus has been disclosed in U.S.
Pat. No. 7,343,770, which was commonly assigned to the assignee of
the present invention. This patent is fully incorporated by
reference as if fully set forth herein. The process and stamping
apparatus disclosed therein may be adapted to precision stamping
the features of the ferrule 40 and cover 42 of the present
invention. The stamping process and system can produce parts with a
tolerance of at least 1000 nm.
[0058] FIG. 5D illustrates an alternate embodiment, in which
complementary alignment grooves 34' and 34'' (e.g., grooves having
C-shaped or semi-circular cross-section) are provided on the
ferrule portions 40' and 42', respectively. The grooves 34' and
34'' may be symmetrical or asymmetrical with respect to the contact
interface between the ferrule portions 40' and 42'' in the end view
of FIG. 5D (or sectional view orthogonal to the longitudinal axis
of the grooves). The ferrule portions 40' and 42'' may be identical
in an alternate embodiment. Alternatively, grooves having V-shaped
cross-section could be used instead of U-shaped or C-shaped grooves
in the ferrule 40, cover 42, and/or ferrule portions 40' and
42'.
[0059] Instead of providing an aperture in the ferrule 40 for
feeding glass solder, such aperture may be provided in the cover 42
instead, or in addition. Further, the cavity 48 may be defined by a
pocket provided in only one of the ferrule 40 and the cover 42.
Alternatively, instead of wells defining the pockets 44 and 54,
grooves of significant larger size may be provided in the cover 42
and/or ferrule 40 bridging the grooves 34 and 35 (i.e., large
clearances between optical fibers 24 and the larger grooves to
facilitate flow of sealant to hermetically, internally plug the
assembly).
[0060] While the above embodiments are directed to a hermetic
multi-fiber ferrule assembly, the present inventive concept is
equally applicable to a hermetic single-fiber ferrule assembly.
[0061] FIGS. 10A and 10B are perspective views of a light directing
element at the end of the optical fibers 24 in the hermetic optical
fiber assembly 10 discussed above; FIG. 10C is a sectional view
taken along line 10C-10C in FIG. 10B. A separate mirror assembly 57
(schematically shown) is positioned and aligned with the ends of
the optical fibers 24, to direct light input/output between the
fiber ends and an opto-electronic device 58 (schematically shown),
such as a transmitter (e.g., a laser such as a VCSEL--Vertical
Cavity Surface-Emitting Laser) or a receiver (e.g., photodetector).
These opto-electronic devices convert between electrical signals
and optical signals, and are contained in the opto-electronic
module 12. FIG. 13 is a sectional view showing additional detail of
the mounting of the hermetic optical fiber assembly 10 through the
openings (21, 22) in the base 16 of opto-electronic module housing
14, in accordance with another embodiment of the present
invention.
[0062] The mirror assembly 57 may be attached to the assembly 10,
and the input/output of the mirror assembly 57 is positioned and
aligned with respect to the opto-electronic device 58.
Alternatively, the mirror assembly 57 is supported within the
module 12 and aligned with respect to the opto-electronic device
58, with the hermetic assembly 10 aligned to the mirror assembly
57. Reference also to FIG. 3, the hermetic assembly 10 is
hermetically sealed to the module housing base 16. The hermetic
assembly 10 may be deemed to function both as a feedthrough and as
an alignment ferrule for the optic fiber ribbon 23.
[0063] While the above described embodiments are described in
reference to a hermetic ferrule assembly that has a generally
rectangular cross-section, other cross-sectional geometry may be
implemented without departing from the scope and spirit of the
present invention.
[0064] Referring to embodiment illustrated in FIG. 11, the hermetic
ferrule assembly may have a generally oval cross-section. The
structure of the hermetic assembly 60 may be similar to the
hermetic assembly 10 in the earlier embodiments, except that the
external cross-sectional profile is generally oval. The hermetic
assembly 60 includes two ferrule portions which together make up
the hermetic assembly having the oval cross-section. One of the
ferrule portions may correspond to the cover 42 in the prior
embodiment (having similar surface features as the underside 38)
and the other one of the ferrule portions may correspond the
ferrule 40 in the prior embodiment (having similar surface features
as the underside 39). In this embodiment, instead of providing the
hermetic ferrule assembly connected to a optic fiber ribbon 23 as
in the prior embodiments, the hermetic ferrule assembly 60 is
hermetically attached to the housing 14 of the opto-electronic
module 12, having only bare optical fibers 24 (i.e., without buffer
and protection layers) held within the assembly 60 without
extending at both ends appreciably beyond the assembly 60 (i.e.,
the optical fibers held in the assembly 60 terminates substantially
coplanar with both end faces of the assembly 60; one of the end
faces of the assembly 60 being inside the module housing 14). In
this embodiment, the fiber alignment grooves would be precisely
formed (e.g., by stamping) at high tolerance for both ends of the
optical fibers. Alternatively, the oval hermetic assembly in FIG.
11 may be replaced with the hermetic assembly 10 in the prior
embodiment, in which case an alignment sleeve having a generally
rectangular cross-section would be required.
[0065] Accordingly, in this embodiment, the hermetic ferrule
assembly 60 provides a demountable terminal for the module 12, for
coupling to another optical device, such as an optical fiber ribbon
(e.g., a patch cord 63 having similarly shaped ferrules having oval
cross-section), by using an alignment sleeve 62 (e.g., a split
sleeve having complementary shape sized to receive the ferrule
assembly 60 and the ferrule on the patch cord 63). In this
embodiment, the hermetic assembly 60 may be deemed to be a hermetic
terminal of the module 12 having an alignment ferrule for optical
alignment to external devices. With this embodiment, a defective
external optical fiber ribbon may be replaced by plugging a
replacement fiber ribbon onto the hermetical ferrule terminal.
[0066] In yet another aspect of the present invention, an improved
hermetic optical fiber alignment assembly includes an integrated
optical element for coupling the input/output of an optical fiber
to the opto-electronic devices in the opto-electronic module.
Instead of a separate, external optical module (e.g., mirror module
57) in the embodiments of FIGS. 10 and 13, the improved hermetic
optical fiber alignment assembly includes an integrated optical
element (e.g., the optical element and the ferrule portion are part
of the same monolithic structure). In one embodiment, the
integrated optical element comprises a reflective element that is
stamped with the alignment groove for the optical fiber in the
ferrule portion of the hermetic optical fiber alignment assembly.
In the embodiments discussed below, the optical element is a
structured reflective surface that is an integral extension from
the alignment groove in the ferrule in the above discussed
embodiments of the hermetic optical fiber alignment assemblies. The
end of the optical fiber is at a defined distance to and aligned
with the structured reflective surface. The reflective surface
directs light to/from the input/output ends of the optical fiber by
reflection. The open structure open structure of the structured
reflective surface and fiber alignment groove lends itself to mass
production processes such as precision stamping.
[0067] The present invention adopts the concept of stamping optical
elements disclosed in the earlier filed copending U.S. patent
application Ser. No. 13/786,448 (to which priority has been
claimed), which had been fully incorporated by reference
herein.
[0068] In the embodiment illustrated in FIGS. 14 and 15, the
hermetic optical fiber alignment assembly 110 has similar structure
as the hermetic assembly 10 disclosed above, with the exception
that instead of terminating the optical fibers 24 at an end face of
the assembly, the ferrule is extended such that the alignment
grooves extends to structured reflective surfaces and the ends of
the optical fibers 24 are positioned in relation to the structured
reflective surfaces. The hermetic optical fiber alignment assembly
110 includes a ferrule 140 and a cover 142, which are essentially
similar in structure to the ferrule 40 and cover 142 in the prior
embodiments, with the exception of the extended structure of the
ferrule 140. The end of the ferrule 140 near the terminating ends
of the optical fibers 24 is not coplanar with the end of the cover
142. The ferrule 142 has a portion 70 that extends beyond the
adjacent end of the cover 142. Referring to FIG. 15, the ferrule
142 is provided with fiber alignment grooves 134 that extend beyond
the edge of the cover to the extended portion 70. Each groove 134
terminates in a structured reflective surface 113 located beyond
the adjacent edge of the cover 142. Each optical fiber 124 extends
in the groove 134 to beyond the edge of the cover 142, to closer to
the structured reflective surface 113. FIG. 6 illustrates an
enlarged view of the extended portion 70.
[0069] FIG. 17A is a sectional view taken along the longitudinal
axis of the optical fiber 10. FIG. 17B is a perspective section
view taken along the longitudinal axis of the optical fiber 10. In
the illustrated embodiment, the fiber alignment groove 134
positively receives the optical fiber 24 in a manner with the end
of the optical fiber 24 at a defined distance to and aligned with
the structured reflective surface 113. The location and orientation
of the structured reflective surface 113 is fixed in relation to
the fiber alignment groove 134. In the illustrated embodiment, the
groove 134 and the structured reflective surface 113 are defined on
the same (e.g., monolithic) ferrule 140. The groove 134 has a
section 124 defining a space between the end face 15 of the optical
fiber 24. In the illustrated embodiment, this section 124 has a
similar width but a shallower bottom as the remaining sections of
the groove 134. The section 124 defines a shoulder 127 that
provides a stop against which a portion (end) of the end face 113
of the optical fiber 24 is butted. Accordingly, a distance (e.g.,
245 .mu.m) along the optical axis is defined between the end face
115 and the structured reflective surface 113. In the illustrated
embodiment, the optical fiber is completely received in the groove
134, with the exterior surface of the optical fiber 24 flush with
the top surface 139 of the ferrule 140. Given an optical fiber
having a diameter of 125 p.m, and a VCSEL light source 158 at an
effective distance (e.g., from the flat surface of the VCSEL 158
along the optical axis) of 100 p.m from the structured reflective
surface 113, the distance of the flat surface of the VCSEL 158 from
the top surface 139 of the ferrule would be about 37.5 .mu.m.
[0070] The design considerations of the open groove 134 are similar
to the grooves 34 in the earlier embodiments (e.g., a generally
U-shaped cross-section that snuggly receive the bare optical fiber
24, etc. The design considerations for the structured reflective
surface are similar to those disclosed in copending U.S. patent
application Ser. No. 13/786,448.
[0071] The hermetic assembly 110 is attached to the opening (21,
22) in the base 16 of the housing 14 of the opto-electronic module
12, with the extended portion 70 within the module housing 14. The
reflective surface 113 is in optical alignment with the
opto-electronic device 58. FIG. 18 illustrates a close up sectional
view of the structured reflective surface region. In this
embodiment, the structured reflective surface is a flat mirror
surface, which reflects light 159 to/from the optical fiber 24
from/to the opto-electronic device 58. FIG. 19 is a sectional view
illustrating the reflection of light between optical fiber 24 and
the opto-electronic device 58 via structured reflective surface 113
at the extended portion 70, which is a concave reflective surface
that reflect incident light in a converging manner.
[0072] The hermetic assembly 110 may be deemed to function as a
feedthrough with built-in optics and an alignment ferrule for the
optic fiber ribbon 23, eliminating the need for separate optical
elements for optical coupling with the opto-electronic devices
(e.g., transmitter and receiver) in the opto-electronic module
12.
[0073] The structured reflective surface 113 and the alignment
grooves 134 may be formed integrally by precision stamping a
ferrule out of a metal material. A precision stamping process and
apparatus has been disclosed in U.S. Pat. No. 7,343,770, which was
commonly assigned to the assignee of the present invention. This
patent is fully incorporated by reference as if fully set forth
herein. The process and stamping apparatus disclosed therein may be
adapted to precision stamping the features of the ferrule 140
and/or cover 142 of the present invention (including the structured
reflective surfaces and optical fiber alignment grooves). The
stamping process and system can produce parts with a tolerance of
at least 1000 nm.
[0074] For the hermetic assemblies described above that are
configured for optical alignment/coupling to optical fibers in
another fiber ribbon, the external surfaces of the hermetic
assemblies should be maintained at high tolerance as well for
alignment using an alignment sleeve. In the embodiments described
above, no alignment pin is required for alignment of the ferrules.
Accordingly, for stamping of the ferrule portions (ferrules and
covers), that would include stamping the entire body of the ferrule
portions, including forming the grooves, mating surfaces of the
ferrule portions, and external surfaces that come into contact with
sleeves. The sleeves may be precision formed by stamping as well.
This maintains the required dimensional relationship between the
grooves and external alignment surfaces of the hermetic assemblies,
to facilitate alignment using alignment sleeves only without
relying on alignment pins.
[0075] In all the above described embodiments, the structured
reflective surface 113 may be configured to be flat, concave or
convex, or a combination of such to structure a compound reflective
surface. In one embodiment, the structured reflective surface has a
smooth (polished finish) mirror surface. It may instead be a
textured surface that is reflective. The structured reflective
surface may have a uniform surface characteristic, or varying
surface characteristics, such as varying degree of smoothness
and/or textures across the surface, or a combination of various
regions of smooth and textured surfaces making up the structured
reflective surface. The structured reflective surface may have a
surface profile and/or optical characteristic corresponding to at
least one of the following equivalent optical element: mirror,
focusing lens, diverging lens, diffraction grating, or a
combination of the foregoing. The structure reflective surface may
have a compound profile defining more than one region corresponding
to a different equivalent optical element (e.g., a central region
that is focusing surrounded by an annular region that is
diverging). In one embodiment, the structured reflective surface is
defined on an opaque material that does not transmit light through
the surface.
[0076] The hermetic assemblies described in earlier embodiments may
be further provided with an integral optical element in similar
fashion. For example the hermetic assembly 60 in FIG. 11 may adopt
an integral optical element (e.g., a stamped structured reflective
surface) similar to the assembly 110.
[0077] The hermetic optical fiber alignment assembly in accordance
with the present invention overcomes many of the deficiencies of
the prior art, which provides precision alignment, high reliability
against environmental conditions, and which can be fabricated at
low cost. The inventive hermetic assembly may be configured to
support a single or multiple fibers, for optical alignment and/or
hermetic feedthrough that may include integral optical
elements.
[0078] While the invention has been particularly shown and
described with reference to the preferred embodiments, it will be
understood by those skilled in the art that various changes in form
and detail may be made without departing from the spirit, scope,
and teaching of the invention. Accordingly, the disclosed invention
is to be considered merely as illustrative and limited in scope
only as specified in the appended claims.
* * * * *