U.S. patent application number 11/485452 was filed with the patent office on 2006-11-16 for connection of optical waveguides to optical devices.
This patent application is currently assigned to FIRECOMMS LIMITED. Invention is credited to Brian McGarvey, Thomas Moriarty.
Application Number | 20060257082 11/485452 |
Document ID | / |
Family ID | 32170646 |
Filed Date | 2006-11-16 |
United States Patent
Application |
20060257082 |
Kind Code |
A1 |
McGarvey; Brian ; et
al. |
November 16, 2006 |
Connection of optical waveguides to optical devices
Abstract
An optical assembly has a socket for receiving a fibre
termination ferrule. A PIN diode is on a lead frame encapsulated in
a transparent body. As a fibre ferrule is pushed into the socket
the electronic output from the diode is monitored to determine
optimum insertion distance.
Inventors: |
McGarvey; Brian; (County
Cork, IE) ; Moriarty; Thomas; (Cork, IE) |
Correspondence
Address: |
JACOBSON HOLMAN PLLC
400 SEVENTH STREET N.W.
SUITE 600
WASHINGTON
DC
20004
US
|
Assignee: |
FIRECOMMS LIMITED
|
Family ID: |
32170646 |
Appl. No.: |
11/485452 |
Filed: |
July 13, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11109674 |
Apr 20, 2005 |
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11485452 |
Jul 13, 2006 |
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PCT/IE03/00144 |
Oct 21, 2003 |
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11109674 |
Apr 20, 2005 |
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Current U.S.
Class: |
385/92 ;
385/88 |
Current CPC
Class: |
G02B 6/423 20130101;
G02B 6/4253 20130101; G02B 6/4255 20130101; G02B 6/4292 20130101;
G02B 6/4239 20130101; G02B 6/4201 20130101; G02B 6/4212
20130101 |
Class at
Publication: |
385/092 ;
385/088 |
International
Class: |
G02B 6/36 20060101
G02B006/36 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 22, 2002 |
IE |
2002/0826 |
Claims
1-21. (canceled)
22. An optical assembly for connection to a fiber termination, the
assembly comprising: a body, a socket in the body to receive a
fiber termination, an optical device supported by the body in fixed
position in relation to the socket, a mirror for direction of light
between the optical device and the socket, wherein the body is of
transparent material, and wherein the mirror is located for
reflection of light within the body.
23. The optical assembly as claimed in claim 22, wherein the
optical device is embedded in the body.
24. The optical assembly as claimed in claim 22, wherein the
optical device is embedded in the body, and is in a plane parallel
to a fiber axis of the socket.
25. The optical assembly as claimed in claim 22, wherein the mirror
is embedded in the body and lies along a surface of the body.
26. The optical assembly as claimed in claim 22, further comprising
a lead frame comprising splayed-out terminals and being
electrically connected to the optical device.
27. The optical assembly as claimed in claim 22, wherein the
optical device is a transmitter.
28. The optical assembly as claimed in claim 22, wherein the socket
is of open V-shaped configuration.
29. The optical assembly as claimed in claim 22, wherein the socket
is shaped for a friction fit of a fiber termination.
30. The optical assembly as claimed in claim 22, wherein the socket
is blind, having an end face; and wherein the body comprises a vent
for excess fiber-bonding epoxy during insertion of a fiber.
31. The optical assembly as claimed in claim 22, wherein the socket
is blind, having an end face; and wherein the body comprises a vent
for excess fiber-bonding epoxy during insertion of a fiber; and
wherein the vent extends at right angles to the axial direction of
the blind socket.
32. The optical assembly as claimed in claim 22, wherein the socket
is blind, having an end face; and wherein the body comprises a vent
for excess fiber-bonding epoxy during insertion of a fiber; and
wherein the vent is in a shape of an elongate slot extending for at
least part of the length of the blind socket.
33. The optical assembly as claimed in claim 22, wherein the socket
is of circular cross-section having a diameter matching that of a
fiber termination for a friction fit, and the cross-sectional shape
is uniform along the length of the blind socket.
34. The optical assembly as claimed in claim 22, wherein the
optical device is mounted on an electrical lead frame, and the lead
frame supports an insulation plate, and the optical device is
mounted on the insulation plate.
35. The optical assembly as claimed in claim 22, wherein the
optical device is mounted on an electrical lead frame, and the lead
frame supports at least one decoupling capacitor embedded within
the body.
36. The optical assembly as claimed in claim 22, wherein the
optical device is mounted on an electrical lead frame, and the lead
frame is of generally rectangular overall shape, and there is a
decoupling capacitor at two corners of the lead frame.
37. An optical fiber product comprising an assembly as claimed in
claim 22 and an optical fiber having a termination inserted in the
socket and secured in place by a bonding agent.
38. A method of connecting a fiber termination to the optical
assembly as claimed in claim 30, the method comprising the steps
of: applying a bonding composition to one of the fiber termination
and the blind socket, pushing the fiber termination into the blind
socket until an optimum position is reached at which optical
coupling between the fiber and the optical device in the assembly
is satisfactory, and curing the bonding composition while retaining
the fiber termination at an optimum position.
39. The method as claimed in claim 38, wherein the optical device
is an opto-electronic receiver device, a test optical signal is
directed through the fiber, and an electronic signal output of said
device is monitored to determine the optimum fiber termination
position.
40. The method as claimed in claim 38, wherein the optical device
is an opto-electronic receiver device, a test optical signal is
directed through the fiber, and an electronic signal output of said
device is monitored to determine the optimum fiber termination
position; and wherein the optical device is a transmitter, and
light output at the far end of the fiber is monitored to determine
the optimum fiber termination position.
Description
INTRODUCTION
[0001] 1. Field of the Invention
[0002] The invention relates to connection of optical devices to
terminations of optical waveguides for transmitting and/or
receiving data or for coupling to other waveguides.
[0003] 2. Prior Art Discussion
[0004] It is known to provide an optical fibre having a ferrule at
its end, and a coupler for guiding the ferrule into a socket for an
optical device. Typically, there is a snap-fitting fastener
arrangement between the ferrule and the socket, and the socket is
tapered internally to guide the fibre termination into
registry.
[0005] This arrangement allows fibres to be coupled to devices in
the field. However, while this is convenient it is often the case
that coupling efficiency degrades over time due to contamination at
the fibre termination and/or in the socket because they are
exposed.
[0006] Patent Abstracts of Japan 10282369 describes a coupler
having a laser device. Resin is filled over the laser device, an
optical fibre, a photodetector, and a silicon substrate. A resin
lid is used to cover the resin case. U.S. Pat. No. 6,312,624
describes an arrangement whereby a body is moulded to a substrate,
the body having a functional surface for optical coupling. The body
also has receiving sleeve for retaining the end of a waveguide by
resilience. It appears that such an arrangement could cause
deformation of the end of the waveguide.
[0007] U.S. Pat. No. 6,170,996 describes an optical module in which
a fibre termination is placed on a V-groove and a resin is
dispersed over an optical component and the fibre end face. A
second rein may then be moulded over the whole module. This
arrangement appears to be complex.
[0008] The invention addresses this problem.
SUMMARY OF THE INVENTION
[0009] According to the invention, there is provided an optical
assembly for connection to a fibre termination, the assembly
comprising a body comprising a socket to receive a fibre
termination, and the body supports an optical device in fixed
position in relation to the socket.
[0010] In one embodiment, the socket is shaped for a friction fit
of a fibre termination.
[0011] In another embodiment, the body comprises a vent for excess
fibre-bonding epoxy during insertion of a fibre.
[0012] In a further embodiment, the vent extends at right angles to
the axial direction of the socket.
[0013] In one embodiment, the vent is in the shape of an elongate
slot extending for at least part of the length of the socket.
[0014] In another embodiment, the socket is of circular
cross-section having a diameter matching that of a fibre
termination for a friction fit, and the cross-sectional shape is
uniform along the length of the socket.
[0015] In a further embodiment, the optical device is mounted on an
electrical lead frame.
[0016] In one embodiment, part of the lead frame is encapsulated in
the body, and electrical terminals of the lead frame protrude from
the body.
[0017] In another embodiment, the lead frame extends substantially
parallel to an end face of the socket.
[0018] In a further embodiment, the lead frame supports an
insulation plate, and the optical device is mounted on the
insulation plate.
[0019] In one embodiment, the lead frame supports at least one
decoupling capacitor embedded within the body.
[0020] In another embodiment, the lead frame is of generally
rectangular overall shape, and there is a decoupling capacitor at
two corners of the lead frame.
[0021] In a further embodiment, there is a gap of body material
between the optical device and a socket end face.
[0022] In one embodiment, the socket has a planar end face.
[0023] In another embodiment, the assembly further comprises a
mirror for direction of light between the optical device and the
fibre.
[0024] In a further embodiment, the socket is of open V-shaped
configuration.
[0025] In another aspect, the invention provides an optical fibre
product comprising an assembly as defined above and an optical
fibre having a termination inserted in the socket and secured in
place by a bonding agent.
[0026] In one embodiment, said body forms part of an optical path
between the fibre and the optical device.
[0027] In another embodiment, the method comprises the steps of:
[0028] applying a bonding composition to the fibre termination or
to the socket, [0029] pushing the fibre termination into the socket
until an optimum position is reached at which optical coupling
between the fibre and the optical device in the assembly is
satisfactory, and [0030] curing the bonding composition while
retaining the fibre termination at the optimum position.
[0031] In a further embodiment, the optical device is an
opto-electronic receiver device, a test optical signal is directed
through the fibre, and an electronic signal output of said device
is monitored to determine the optimum fibre termination
position.
[0032] In one embodiment, the optical device is a transmitter, and
light output at the far end of the fibre is monitored to determine
the optimum fibre termination position.
DETAILED DESCRIPTION OF THE INVENTION
Brief Description of the Drawings
[0033] The invention will be more dearly understood from the
following description of some embodiments thereof, given by way of
example only with reference to the accompanying drawings in
which:
[0034] FIGS. 1 to 4 are perspective, end, side, and underneath plan
views respectively of an optical subassembly for connection to a
fibre termination;
[0035] FIGS. 5, 6, 7, and 8 are perspective, front, side, and plan
views respectively of a lead frame of the subassembly;
[0036] FIG. 9 is a diagram illustrating optical coupling;
[0037] FIG. 10 is a set of plots illustrating coupling efficiency
as a function of the distance between the end of the fibre and the
optical device;
[0038] FIG. 11 is a diagrammatic side view of an alternative
subassembly;
[0039] FIGS. 12(a) to 12(b) are views of an alternative
subassembly; and
[0040] FIGS. 13(a) to 13(c) are views of a further subassembly.
DESCRIPTION OF THE EMBODIMENTS
[0041] Referring to FIGS. 1 to 8, an optical subassembly 1 is for
permanent connection to a fibre termination and for releasable
electrical connection to the remainder of a transceiver. The
subassembly 1 comprises a moulded plastics body 2 of transparent
thermoset epoxy material within which there is a socket 3 of
uniform circular cross section, matched in diameter with a fibre
termination ferrule to fit into the socket 3. The body 2 has a slot
4 running along the length of the socket 3.
[0042] The subassembly 1 also comprises a lead frame 5 encapsulated
in the body 2. The lead frame 5 comprises Cu alloy terminals 10 in
a rigid structure. This structure supports a PIN photodiode 11 and
a trans-impedance amplifier (TIA) 12 mounted on a ceramic
insulating plate 13. Capacitors 14 and 15 are mounted in the
corners for decoupling.
[0043] The lead frame 5 is encapsulated in the (transparent) body 2
so that the PIN diode 11 is in alignment with the central axis of
the socket 3. The encapsulation of the lead frame 5 leaves a
spacing of the transparent body material between the PIN diode 11
and the end of the socket 3.
[0044] Connection of a fibre termination ferrule F to the
subassembly 1 is very simple, as shown in FIG. 3. An epoxy is
applied to the outer surface of the ferrule F. The ferrule F is
gradually pushed, either manually or by robot, into the socket 3.
The fit is a tight, friction fit leaving little or no space for
radial variation. The epoxy 21 forms a thin film surrounding at
least some of the outer surface of the ferrule F.
[0045] As the ferrule F is inserted into the socket 3 a test light
signal is directed through the fibre towards this termination. The
corresponding electronic TIA output is monitored continually as the
ferrule is inserted. The amplitude of the TIA output reaches a peak
for a certain insertion distance of the fibre because of the
relationship between the positions of the PIN diode 11 and the
ferrule end. As shown in FIG. 9 there is a "field of view" cone of
emitted light extending through the body 2 and encompassing the PIN
diode 11. Likewise, if the optical device were a transmitter the
same principle applies in reverse as shown in this diagram.
[0046] It will be appreciated that the PIN diode 11 may be
mis-aligned from the central axis of the fibre by some microns.
However, it will still be in the cone and is in a maximum of light
intensity for a certain distance between the end of the ferrule F
and the end of the socket 3. FIG. 10 shows plots of coupling
efficiency versus fibre insertion distance for three values of
relative misalignment from the centre of the fibre. Thus, for any
one misalignment value there is a particular optimum insertion
distance of the ferrule. This can be determined by simply
monitoring the TIA output as the ferrule is pushed in. This can be
done by measuring the DC bias voltage on the monitor pin of a post
limiting amplifier (PLA) which is in the transceiver circuit
outside of the assembly 1.
[0047] When the optimum position is reached the epoxy is cured by
application of UV, effectively "freezing" the ferrule in
position.
[0048] FIG. 9 shows an equivalent "field of view" cone for an
embodiment in which the subassembly comprises a transmitter. In
this embodiment, as the fibre is pushed the light output at the far
end is monitored to determine the optimum position.
[0049] The optimum gap between the fibre end and the optical device
is a unique parameter for each optical device. In the case of the
transmitting device it depends on the positioning of the device and
the divergence angle of the optical beam. In the case of the
receiving device it depends on the positioning of the device and
the numerical aperture of the fibre.
[0050] The end of the lead frame distant from the body 2 has a
lateral end piece. The purpose of this is to hold the lead frame
together during manufacture. This is cut off at an appropriate
stage in the production process to leave separate terminal
pins.
[0051] Alternative embodiments within the scope of the invention
will be apparent to those skilled in the art. Referring to FIG. 11,
in another embodiment a subassembly 30 has a body 31 and a lead
frame 32. A socket 33 is linked with a vent duct 34 for excess
epoxy 35. Epoxy 35 is inserted into the socket 33. As the ferrule F
is inserted, some of the epoxy 35 is pushed into the gap separating
the end of the ferrule F from the end of the socket 33 and some is
in thin film around the ferrule. Excess epoxy is allowed escape
into the vent duct 34. Thus, there is a quantity of epoxy in the
gap at the end of the ferrule F. The epoxy is index matched to the
glass (or plastic) core of the fibre so that losses are minimised
in the subassembly. The duct 34 allows the ferrule F to be pushed
in to any desired depth.
[0052] Referring to FIGS. 12(a) to 12(d) inclusive an optical
assembly 50 comprises a V-shaped socket 52 in a body 51. The socket
52 can align the fibre in an X-Y plane vertically through the
socket to allow Z adjustment as the fibre is inserted. In this
arrangement the fibre ferrule may be easily placed as it may be
inserted from above or axially as desired. In this, as in previous
embodiments, the epoxy may be applied either to the ferrule or to
the socket.
[0053] Referring to FIGS. 13(a) to 13(c) an optical assembly 60 has
a V-shaped socket 61 and a reflector 62 arranged to re-direct light
from a transmitter 70 into a ferrule F placed in the socket 61. In
this embodiment the lead frame comprises splayed-out terminals 63.
Advantages of this arrangement are that is minimises the height of
the overall package. All electronic/optical components are in a
plane parallel to the fibre, thus minimising depth of the overall
assembly.
[0054] A complete communication link having a transmitter, a fibre,
and a receiver may be completed with optimum coupling at both ends
of the fibre. For example, the fibre may be inserted in the
transmit end first without monitoring. The receive end of the fibre
is then inserted with monitoring to set the optimum position, the
position being "frozen" by UV curing. The fibre at the transmit end
is then adjusted to "fine tune" the link and provide an attenuation
budget which is greater than a given minimum.
[0055] It will be appreciated that there are significant advantages
to the invention. The end user is provided with an integral fibre
and fixed optical coupling at its termination. To complete a
connector it is only necessary to simply push fit the lead frame 5
into a corresponding electrical socket in the other part of the
connector. This also allows modularity. No optical interconnection
or coupling is required by the end user and so risk of
contamination is reduced. Another advantage is that the
manufacturer has the benefit of being able to monitor and guarantee
the coupling efficiency of the connection. The epoxy has the same
optical properties before and after curing so that the performance
monitored at the TIA output in consistently achieved during the
product lifetime. The method of inserting and bonding the fibre
termination compensates for slight mis-alignments of the
opto-electronic device 5 and an off-perpendicular end face of the
fibre.
[0056] The invention is not limited to the embodiments described
but may be varied in construction and detail. For example, the
socket may have two or more sections, one suited to a larger
diameter than another, so that one can support the bare fibre, or
the fibre in a ferrule, while the other supports the fibre inside a
jacket which runs for most of the length of the fibre, or a sleeve
placed over part of the ferrule.
[0057] Also, where a mirror is used for coupling light to or from
the fibre, the mirror may be curved (e.g. parabolic) for effective
focusing. Also, the socket may have sufficient length and diameter
so that is supports both a ferrule and a jacketing of the fibre. In
this example, the socket may be stepped to accommodate the
different diameters. Furthermore, the electrical pins may be
suitable for soldering or fixing by conductive epoxy or similar
means. Also, the body may be of any suitable transparent material
such as thermoplastic resins, thermoset epoxies, and two-part
epoxies. Also, the optical device may be protected against ingress
of contaminants from the body during moulding. Such protection may
comprise silicon oxide, atmosphere pressure oxide, silica gel, or
other material.
* * * * *