U.S. patent application number 14/968841 was filed with the patent office on 2016-06-30 for hermetic optical fiber alignment assembly.
The applicant listed for this patent is NANOPRECISION PRODUCTS, INC.. Invention is credited to Michael K. BARNOSKI, Shuhe LI, Robert Ryan VALLANCE.
Application Number | 20160187599 14/968841 |
Document ID | / |
Family ID | 49517621 |
Filed Date | 2016-06-30 |
United States Patent
Application |
20160187599 |
Kind Code |
A1 |
LI; Shuhe ; et al. |
June 30, 2016 |
HERMETIC OPTICAL FIBER ALIGNMENT ASSEMBLY
Abstract
A hermetic optical fiber alignment assembly, including a first
ferrule portion having a first surface provided with 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 first ferrule portion, and 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. 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. In another aspect, the hermetic assembly provides
optical alignment and a hermetic feedthrough for an opto-electronic
module. In a further aspect, the hermetic assembly provides
alignment and a terminal for access to an opto-electronic
module.
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. |
El Segundo |
CA |
US |
|
|
Family ID: |
49517621 |
Appl. No.: |
14/968841 |
Filed: |
December 14, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13861268 |
Apr 11, 2013 |
9213148 |
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14968841 |
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61623027 |
Apr 11, 2012 |
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61699125 |
Sep 10, 2012 |
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Current U.S.
Class: |
385/89 ;
264/1.25 |
Current CPC
Class: |
G02B 6/4292 20130101;
G02B 6/3839 20130101; Y10T 29/4998 20150115; G02B 6/4219 20130101;
G02B 6/3885 20130101; G02B 6/4214 20130101; G02B 6/4248 20130101;
G02B 6/3636 20130101; G02B 6/3838 20130101; G02B 6/3861 20130101;
G02B 6/4253 20130101 |
International
Class: |
G02B 6/42 20060101
G02B006/42; G02B 6/38 20060101 G02B006/38 |
Goverment Interests
GOVERNMENT RIGHTS
[0002] This invention was made with government support under
Contract No. N68335-12-C-0123 awarded by NAVAL AIR WARFARE CTR
AIRCRAFT DIVISION. The government has certain rights in the
invention.
Claims
1. 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.
2. The hermetic optical fiber alignment assembly as in claim 1,
wherein the sealant extends around the suspended sections of the
optical fibers within the cavity.
3. The hermetic optical fiber alignment assembly as in claim 2,
wherein 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.
4. The hermetic optical fiber alignment assembly as in claim 3,
wherein the second surface of the second ferrule portion is also
provided with a well defining a second pocket in the second ferrule
portion, wherein the first pocket and the second pocket together
define the cavity.
5. The hermetic optical fiber alignment assembly as in claim 1,
wherein 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.
6. The hermetic optical fiber alignment assembly as in claim 5,
wherein the aperture is sized to be wider than the optical
fibers.
7. The hermetic optical fiber alignment assembly as in claim 1,
wherein each end section of the optical fibers come into contact
with at least the side walls of the grooves at a plurality of
contact points, with no sealant between the optical fiber and the
groove at the contact points.
8. The hermetic optical fiber alignment assembly as in claim 1,
wherein the end sections of the optical fibers terminate
substantially coplanar with a first end face of the first ferrule
portion.
9. The hermetic optical fiber alignment assembly as in claim 1,
wherein the optical fibers terminates substantially coplanar with a
second end face of the first ferrule portion.
10. The hermetic optical fiber alignment assembly as in claim 2,
wherein the optical fibers do not extend beyond the first and
second ferrule sections at another end.
11. The hermetic optical fiber alignment assembly as in claim 1,
wherein at least one of the first ferrule portion and the second
ferrule portion are formed by stamping.
12. The hermetic optical fiber alignment assembly as in claim 11,
wherein at least one of the first ferrule portion and the second
ferrule portion are made of a metal material.
13. An opto-electronic module, comprising: a housing; and a
hermetic optical fiber alignment assembly as in claim 1,
hermetically sealed to the housing.
14. An opto-electronic module, comprising: a housing; and a
hermetic optical fiber alignment assembly as in claim 9,
hermetically sealed to the house, forming a terminal for external
connection by an alignment sleeve.
15. A hermetic optical fiber alignment assembly, comprising: a
first ferrule portion having a first surface provided with 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 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 has a
width wider than the groove, and wherein a suspended section of the
optical fiber is suspended in the cavity, and wherein the cavity is
sealed with a sealant.
16. The hermetic optical fiber alignment assembly as in claim 15,
wherein there are a plurality of optical fibers and a plurality of
grooves each receiving at least the end section of one of the
optical fibers.
17. A method of forming a hermetic optical fiber alignment
assembly, comprising: forming first and second ferrule portions,
wherein the first ferrule portion has 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, and the a second ferrule portion has a
second surface facing the first surface of the first ferrule;
attaching the first ferrule portion 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 sealing the cavity with a sealant.
18. The method of claim 17, wherein an aperture is provided in at
least one of the first and second ferrule portions, wherein the
aperture exposes the cavity, wherein the sealant is feed through
the aperture.
19. The hermetic optical fiber alignment assembly as in claim 18,
wherein the sealant extends around the suspended sections of the
optical fibers within the cavity.
20. The method of claim 19, wherein a vacuum is applied at one end
of the assembly to draw sealant from the cavity into the grooves.
Description
PRIORITY CLAIM
[0001] This application is a continuation of U.S. patent
application Ser. No. 13/861,268 filed on Apr. 11, 2013, which
claims the priority of U.S. Provisional Patent Application No.
61/623,027 filed on Apr. 11, 2012, and U.S. Provisional Patent
Application No. 61/699,125 filed on Sep. 10, 2012, which 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
[0003] 1. Field of the Invention
[0004] The present invention relates to optical fiber ferrule
structures, in particular a hermetic optical fiber alignment
assembly including a ferrule for aligning optical fibers.
[0005] 2. Description of Related Art
[0006] 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.
[0007] 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).
[0008] 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.
[0009] 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.
[0010] 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 allows the optical fiber to pass through 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.
[0011] 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.
[0012] The above noted drawbacks of existing fiber optic data
transmission are exacerbated in multi-channel fiber
transmission.
[0013] 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.
[0014] 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
[0015] 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.
[0016] 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.
[0017] 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.
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 jump 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 jump
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.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0032] 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.
[0033] 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.
[0034] 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.
[0035] 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.
[0036] FIG. 2 is a schematic diagram illustrating an optical jump
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 jump 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 jump patchcord 30 includes two fiber ribbons 23, each
terminating at one end with a hermetic optical fiber 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 jump
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.
[0037] 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.
[0038] 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).
[0039] 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.
[0040] 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.
[0041] 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.
[0042] 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 38 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.
[0043] 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.
[0044] 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.
[0045] 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.
[0046] 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.
[0047] 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.
[0048] 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.
[0049] 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.
[0050] 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.
[0051] 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.
[0052] 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'.
[0053] 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).
[0054] 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.
[0055] 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.
[0056] 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.
[0057] 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.
[0058] 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 optical fibers 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). 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.
[0059] 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.
[0060] 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 the ferrule portions (ferrules and
covers), that would include stamping the entire body of the ferrule
portions, including 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.
[0061] 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.
[0062] 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.
* * * * *