U.S. patent application number 14/837993 was filed with the patent office on 2017-03-02 for multi-channel transmitter optical subassembly (tosa) with opposing placement of transistor outline (to) can laser packages.
The applicant listed for this patent is Applied Optoelectronics, Inc.. Invention is credited to I-Lung Ho, Kai-Sheng LIN, Chong WANG.
Application Number | 20170063464 14/837993 |
Document ID | / |
Family ID | 58096116 |
Filed Date | 2017-03-02 |
United States Patent
Application |
20170063464 |
Kind Code |
A1 |
Ho; I-Lung ; et al. |
March 2, 2017 |
MULTI-CHANNEL TRANSMITTER OPTICAL SUBASSEMBLY (TOSA) WITH OPPOSING
PLACEMENT OF TRANSISTOR OUTLINE (TO) CAN LASER PACKAGES
Abstract
A multi-channel transmitter optical subassembly (TOSA) including
staggered transistor outline (TO) can laser package placement to
provide enhanced coupling and optical power is disclosed, and may
be used in an optical transceiver for transmitting an optical
signal. The TOSA comprises a housing that includes plurality of
sidewall openings with each sidewall opening configured to couple
to a TO can laser package to provide coarse wavelength division
multiplexing. The housing includes at least first and second
sidewall openings on a first sidewall, and a third sidewall opening
disposed on a sidewall opposing the first sidewall and being
positioned at generally a mid-point between the first and second
sidewall openings. This staggered and opposing sidewall opening
arrangement allows an increased distance between adjacent sidewall
openings, and thus, the TOSA may increase optical power and yield
by providing additional space for performing post-attachment
alignment of TO can laser packages.
Inventors: |
Ho; I-Lung; (Sugar Land,
TX) ; LIN; Kai-Sheng; (Sugar Land, TX) ; WANG;
Chong; (Stafford, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Applied Optoelectronics, Inc. |
Sugar Land |
TX |
US |
|
|
Family ID: |
58096116 |
Appl. No.: |
14/837993 |
Filed: |
August 27, 2015 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G02B 5/26 20130101; H04J
14/02 20130101; H01S 5/02212 20130101; H04B 10/40 20130101; G02B
6/3831 20130101; H01S 5/0078 20130101; G02B 6/4263 20130101; G02B
6/423 20130101; G02B 6/4292 20130101; H01S 5/4087 20130101; H01S
5/02288 20130101; G02B 7/006 20130101; G02B 6/4246 20130101; H01S
5/02284 20130101 |
International
Class: |
H04B 10/40 20060101
H04B010/40; G02B 7/00 20060101 G02B007/00; H01S 5/00 20060101
H01S005/00; G02B 5/26 20060101 G02B005/26; H01S 5/022 20060101
H01S005/022; H01S 5/40 20060101 H01S005/40 |
Claims
1. A transmitter optical subassembly (TOSA) including a plurality
of transistor outline (TO) can laser packages, the TOSA comprising:
a housing including at least a first and second sidewall on
opposite sides of the housing and extending along a first major
axis from a first end to a second end, and forming a compartment
defined by an inner surface therein, the first sidewall including
at least first and second sidewall openings, the second sidewall
including at least a third sidewall opening being positioned
generally at a midpoint between the first and second sidewall
openings; at least first and second TO can laser packages coupled
to the first and second sidewall opening of the first sidewall,
respectively, and a third TO can laser package coupled to the third
sidewall opening and opposing the first and second TO can laser
packages; at least a first filter holder coupled to the first
sidewall between the first and second sidewall openings of the
first and second TO can laser packages, respectively, and wherein
the first filter holder provides a substantially flat surface along
an outer edge of the housing between the first and second TO can
laser packages; and a first filter coupled to the first filter
holder.
2. The TOSA of claim 1, further comprising a third sidewall at the
first end and adjoining the first and second sidewall, the third
sidewall including a fourth sidewall opening and a fourth TO can
laser package coupled thereto.
3. The TOSA of claim 1, further comprising a plurality of welding
rings, wherein the plurality of TO can laser packages are coupled
to respective sidewalls of the housing by the plurality of welding
rings via laser welds.
4. The TOSA of claim 1, wherein the compartment defines a light
path, the light path extending from the first end to at least the
second end.
5. The TOSA of claim 4, wherein each of the plurality of TO can
laser packages includes a laser diode optically aligned to direct
light into the compartment.
6. The TOSA of claim 1, further comprising: a second and third
filter holder coupled to the third sidewall on opposite sides of
the third TO can laser packages relative to each other; and a
second and a third filter coupled to the second and third filter
holders, respectively, wherein each of the first, second and third
filters are configured to align with an associated TO can laser
package to pass and reflect laser light at associated channel
wavelengths.
7. The TOSA of claim 6, wherein each of the second and third filter
holders provide a substantially flat surface along an outer edge of
the housing.
8. The TOSA of claim 1, wherein the compartment includes a focusing
lens aligned with a light path at the second end of the
housing.
9. The TOSA of claim 1, wherein the first and second TO can laser
packages are greater than 1 mm apart.
10. The TOSA of claim 1, wherein the second end includes an optical
coupling receptacle configured to optically couple a signal having
multiple different channel wavelengths to a transmit optical
fiber.
11. An optical transceiver module comprising: a transceiver
housing; a transmitter optical subassembly (TOSA) having a
plurality of transistor outline (TO) can laser packages coupled
thereto and located in the transceiver housing for transmitting
optical signals at different channel wavelengths, the TOSA
comprising: a housing including at least a first and second
sidewall on opposite sides of the housing and extending along a
first major axis from a first end to a second end, and forming a
compartment defined by an inner surface therein, the first sidewall
including at least first and second sidewall openings, the second
sidewall including at least a third sidewall opening being
positioned generally at a midpoint between the first and second
sidewall openings; and at least first and second transistor outline
TO can laser packages coupled to the first and second sidewall
opening of the first sidewall, respectively, and a third TO can
laser package coupled to the third sidewall opening and opposing
the first and second TO can laser packages; a multi-channel
receiver optical assembly (ROSA) located in the transceiver housing
for receiving optical signals at different channel wavelengths; and
wherein the third TO can laser package of the TOSA directly
contacts a surface of the multi-channel ROSA.
12. The optical transceiver of claim 11, further comprising a
transmit connecting circuit electrically connected to the TOSA, and
a receive connecting circuit electrically connected to the
ROSA.
13. The optical transceiver of claim 11, wherein the TOSA further
comprises a plurality of filters within the compartment configured
to provide a multiplexed optical signal having multiple different
wavelengths.
14. The optical transceiver of claim 11, wherein the TOSA further
comprises a third sidewall at the first end and adjoining the first
and second sidewall, the third sidewall including a fourth sidewall
opening and a fourth TO can laser package coupled thereto.
15. The optical transceiver of claim 14, wherein each of the first,
second, third and fourth TO can laser packages are associated with
a channel wavelength of 1290 nm, 1330 nm, 1310 nm, and 1270 nm,
respectively.
16. The optical transceiver of claim 11, the TOSA further comprises
a plurality of welding rings, wherein each of the plurality of TO
can laser packages are coupled to respective sidewalls of the TOSA
housing by the plurality of welding rings via laser welds.
17. The optical transceiver of claim 11, wherein the transceiver is
a Quad Small Form-factor Pluggable (QSFP) transceiver module and
the TOSA is configured to transmit at four different channel
wavelengths at transmission rates of at least about 10 Gbps per
channel and transmission distances of 2 km to at least about 10
km.
18. (canceled)
19. The optical transceiver of claim 11, wherein the first and
second TO can laser packages of the TOSA are greater than 1 mm
apart.
20. The optical transceiver of claim 11, wherein the second end of
the TOSA includes an optical coupling receptacle configured to
optically couple a signal having multiple different channel
wavelengths to a transmit optical fiber.
21. The TOSA of claim 1, wherein the first sidewall includes a
first step portion adjacent the first end of the housing that
defines at least one surface, and wherein the substantially flat
surface provided by the first filter holder along an outer edge of
the housing is offset relative to the at least one surface defined
by the first step portion.
22. The TOSA of claim 21, wherein the third sidewall includes a
second step portion adjacent the first end of the housing, the
first and second step portions defining a tapered region that
extends between the first and second ends of the housing.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is related to co-pending U.S. application
Ser. No. ______ (Attorney Docket No. PAT257US) titled "Receiver
Optical Subassembly Housing With Sidewall Receptacle To Provide
Electrical Isolation Between An Adjacent Transmitter Optical
Subassembly in a Transceiver Housing" filed concurrently herewith,
which is herein incorporated by reference in its entirety.
TECHNICAL FIELD
[0002] The present disclosure relates to laser packages, and more
particularly, to a transmitter optical subassembly (TOSA) with
opposing placement of transistor outline (TO) can laser packages
for coarse wavelength division multiplexing (CWDM) for use in an
optical transceiver.
BACKGROUND INFORMATION
[0003] Optical transceivers are used to transmit and receive
optical signals for various applications including, without
limitation, internet data center, cable TV broadband, and fiber to
the home (FTTH) applications. Optical transceivers provide higher
speeds and bandwidth over longer distances, for example, as
compared to transmission over copper cables. The desire to provide
higher speeds in smaller optical transceiver modules for a lower
cost has presented challenges, for example, with respect to
maintaining optical efficiency (power), thermal management,
insertion loss, and manufacturing yield.
[0004] Optical transceiver modules can include one or more
transmitter optical subassemblies (TOSAs) and receiver optical
subassemblies (ROSAs). TOSAs, for example, can include a plurality
of transistor outline (TO) can laser packages, and can also provide
electrical connections and optical couplings to the laser diode
within those laser packages. One technique for fixedly attaching a
TO can laser package to TOSA housing includes using laser welding.
During the welding process, however, rapid solidification of a
welded region and associated material shrinkage may cause
post-weld-shift (PWS). PWS, even in the order of a few micrometers,
can result in total loss of optical power. Techniques for
correction of PWS can include so-called "laser hammering" that
seeks to counteract misalignment through additional laser welds to
"hammer" fibers into an optimized alignment. This is accomplished,
essentially, by adding additional successive laser welds in
particular locations to use the effects of PWS to "pull" fibers out
of misalignment. A light measurement may be taken between each
successive weld to determine a resulting optical power. Correction
of PWS has become increasingly more complex and expensive during
manufacturing because optical transceivers continue to scale down
in size, and in particular, have less area available for laser
welding/attachment of laser packages.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] These and other features and advantages will be better
understood by reading the following detailed description, taken
together with the drawings wherein:
[0006] FIG. 1 is a perspective view of one approach to a
multi-channel TOSA with multiple TO can laser packages.
[0007] FIG. 2 schematically illustrates an embodiment of an optical
transceiver including a multi-channel TOSA and multi-channel
receiver optical subassembly (ROSA).
[0008] FIG. 3 is a perspective view of an example small form-factor
(SFF) pluggable transceiver with a multi-channel TOSA including TO
can laser packages and a multi-channel ROSA, in accordance with an
embodiment of the present disclosure.
[0009] FIG. 4A is a perspective view of an embodiment of the
multi-channel TOSA for use in the optical transceiver module shown
in FIG. 3.
[0010] FIG. 4B is a cross-sectional view of the multi-channel TOSA
of FIG. 4A, in accordance with an embodiment of the present
disclosure.
[0011] FIG. 5 shows an exploded view of the multi-channel TOSA of
FIGS. 3-4B, in accordance with an embodiment of the present
disclosure.
[0012] FIGS. 6A and 6B show perspective views of a first sidewall
and second sidewall of the multi-channel TOSA of FIGS. 3-4B,
respectively, in accordance with an embodiment of the present
disclosure.
[0013] FIG. 7 shows a perspective view of one example TO can laser
package for use in the multi-channel TOSA of FIGS. 3-5.
DETAILED DESCRIPTION
[0014] A multi-channel transmitter optical subassembly (TOSA)
including staggered TO laser can package placement to provide
enhanced coupling and optical power is disclosed, and may be used
in an optical transceiver for transmitting an optical signal at
multiple different channel wavelengths. The TOSA comprises a
housing made of metal or other thermally conductive material, and
includes a plurality of sidewall openings disposed thereon. Each
sidewall opening is configured to couple to TO can laser packages
and provide coarse wavelength division multiplexing (CWDM). The
housing includes at least a first and second sidewall opening on a
first sidewall of the housing, and a third sidewall opening
disposed on an opposite sidewall opposing the first and second
sidewall opening. The third sidewall opening is positioned at
generally a mid-point between the first and second sidewall
openings such that an axis extending tangent from the third
sidewall opening contacts the second and third sidewall opening.
The first and second sidewall openings are separated by a distance
generally equal to at least half the diameter of each of the
respective sidewall openings. This staggered and opposing sidewall
opening arrangement allows an increased distance between adjacent
sidewall openings, without reducing the channel allocation for the
TOSA. Thus the multi-channel TOSA provides additional space for
performing post-attachment alignment of TO can laser packages
through laser hammering, and other such alignment techniques, which
simplifies those attachment/alignment processes to reduce error
rates, and increase yield.
[0015] As previously discussed, optical components such as TOSAs
continue to scale down in size, and as a result, face numerous
non-trivial issues related to maintaining optical power, yield, and
reliability. For example, FIG. 1 shows one example of a
multi-channel TOSA 100 compatible with a Small Form-factor
Pluggable (SFFP) transceiver. As shown the multi-channel TOSA 100
includes four (4) TO can laser packages 104 arranged on an upper
side-wall of housing 102, thus providing 4 wavelengths/channels for
CWDM. To comport with form factor requirements governed by SFFP
standards, such as the Quad Small Form-factor Pluggable (QSFP)
standard, the distance between adjacent TO can laser packages 104
is relatively small with dimension 106 being generally 0.1 mm. This
means that the approach chosen to fixedly attach TO can laser
packages 104 must effectively operate within this relatively small
dimension with little room for error.
[0016] One suitable approach to fixedly attaching TO can laser
packages includes laser welding using a pulsed neodymium-doped
yttrium aluminium garnet (Nd:YAG) laser. A Nd:YAG laser can achieve
optical alignment and with submicron tolerances over the lifetime
of the TOSA 100, but manufacturing is complex using such a laser
due to the small dimension 106 between TO can laser packages 104.
For example, as shown by angle .theta., a laser welding system has
approximately 87.degree..+-.1.degree. relative to the surface of
the house 102 to generate welds. To correct for misalignment caused
by PWS and to bring TO can laser packages 104 into optical
alignment, additional successive welds are added at specific
positions, which is generally referred to as laser hammering. When
those welds fall within dimension 106, for example, the welding
process is more complex and time consuming. In a more general
sense, the cost and time associated with each manufacturing TOSA
100 is increased by the relatively tiny tolerances afforded by
dimension 106.
[0017] Thus, in accordance with an embodiment, a multi-channel TOSA
including staggered TO can laser package placement to provide
additional space between adjacent TO can laser packages is provided
herein. In some cases, the multi-channel TOSA disclosed herein
includes at least twice the distance between adjacent TO can laser
packages versus other TOSA approaches, such as the one shown in
FIG. 1, thus providing additional space, and importantly, a
wide-range of angles in which to perform initial laser welds and
subsequent "hammer" welds to ensure optimized optical alignment.
The multi-channel TOSA disclosed herein can be utilized within, for
example, transceivers that implement QSFP standards (e.g., 40
GB-LR), and other similarly constrained or otherwise small
form-factor transceivers.
[0018] As used herein, "channel wavelengths" refer to the
wavelengths associated with optical channels and may include a
specified wavelength band around a center wavelength. In one
example, the channel wavelengths may be defined by an International
Telecommunication (ITU) standard such as the ITU-T dense wavelength
division multiplexing (DWDM) grid. The term "coupled" as used
herein refers to any connection, coupling, link or the like and
"optically coupled" refers to coupling such that light from one
element is imparted to another element. Such "coupled" devices are
not necessarily directly connected to one another and may be
separated by intermediate components or devices that may manipulate
or modify such signals.
[0019] Now turning to FIG. 2 there is an optical transceiver 200
consistent with embodiments of the present disclosure. In more
detail, the optical transceiver 200 transmits and receives four (4)
channels using four different channel wavelengths (.lamda..sub.1,
.lamda..sub.2, .lamda..sub.3, .lamda..sub.4) and may be capable of
transmission rates of at least about 10 Gbps per channel. In one
example, the channel wavelengths .lamda..sub.1, .lamda..sub.2,
.lamda..sub.3, .lamda..sub.4 may be 1270 nm, 1290 nm, 1080 nm, and
1330 nm, respectively. The optical transceiver 200 may also be
capable of transmission distances of 2 km to at least about 10 km.
The optical transceiver 200 may be used, for example, in internet
data center applications or fiber to the home (FTTH) applications.
In an embodiment, the optical transceiver 200 implements the
specification SFF-8436 titled "QSFP+ 10 Gbs 4.times. PLUGGABLE
TRANSCEIVER Rev 4.8" (hereinafter QSFP+), published on Oct. 31,
2013 by the Electronic Industries Alliance (EIA).
[0020] This embodiment of the optical transceiver 200 includes a
multi-channel TOSA 302 for transmitting optical signals on
different channel wavelengths and a multi-channel receiver optical
subassembly (ROSA) 230 for receiving optical signals on different
channel wavelengths. The multi-channel TOSA 302 and the
multi-channel ROSA 230 are located in a transceiver housing 202. A
transmit connecting circuit 204 and a receive connecting circuit
208 provide electrical connections to the multi-channel TOSA 302
and the multi-channel ROSA 230, respectively, within the housing
202 and communicate with external systems via data bus 203. In some
cases, data bus 203 is a 38-pin connector that comports with
physical connector QSFP standards and data communication
protocols.
[0021] In any event, the transmit connecting circuit 204 is
electrically connected to the electronic components (e.g., TO can
laser packages) in the multi-channel TOSA 302, and the receive
connecting circuit 208 is electrically connected to the electronic
components (e.g., the photodiode packages) in the multi-channel
ROSA 230. The transmit connecting circuit 204 and the receive
connecting circuit 208 include at least conductive paths to provide
electrical connections and may also include additional circuitry.
The multi-channel TOSA 302 transmits and multiplexes multiple
channel wavelengths and is coupled to an optical interface port
212. The optical interface port 212 may comprise an LC connector
receptacle, although other connector types are also within the
scope of this disclosure. For example, the optical interface port
212 may comprise a multi-fiber push on (MPO) connector
receptacle.
[0022] In cases where the optical interface port 212 comprises a
duplex, or bi-directional, LC receptacle, the LC connector
receptacle provides optical connections to the multi-channel TOSA
302, and provides optical connections to the multi-channel ROSA
230. The LC connector receptacle may be configured to receive and
be coupled to a mating LC connector 214 such that the transmit
optical fiber 222 of the external fibers 224 optically couples to
the multi-channel TOSA 302, and the receive optical fiber 217 of
the external fibers 224 optically couples to the multi-channel ROSA
230.
[0023] The multi-channel TOSA 302 includes multiple TO can laser
packages, discussed in greater detail below, and optics for
producing assigned channel wavelengths and coupling the same into
the transmit optical fiber 222. In particular, the lasers in the
multi-channel TOSA 302 convert electrical data signals (TX_D1 to
TX_D4) received via the transmit connecting circuit 204 into
modulated optical signals transmitted over the transmit optical
fiber 222. The lasers may include, for example, distributed
feedback (DFB) lasers with diffraction gratings. The multi-channel
TOSA 302 may also include monitor photodiodes for monitoring the
light emitted by the lasers. The multi-channel TOSA 302 may further
include one or more temperature control devices, such as a
resistive heater and/or a thermoelectric cooler (TEC), for
controlling a temperature of the lasers, for example, to control or
stabilize the laser wavelengths.
[0024] The multi-channel ROSA 230 includes, for example,
photodiodes, mirrors and filters that can de-multiplex different
channel wavelengths in a received optical signal. The multi-channel
ROSA 230 can detect, amplify, and convert such optical signals
received from the external optical fibers 224, and can provide the
converted optical signals as electrical data signals (RX_D1 to
RX_D4) that are output via the receive connecting circuit 208.
[0025] This embodiment of the optical transceiver 200 includes 4
channels and may be configured for coarse wavelength division
multiplexing (CWDM), although other numbers of channels are
possible.
[0026] Referring to FIG. 3, an example small form-factor (SFF)
pluggable optical transceiver 300 with a multi-channel TOSA
including TO can laser packages and multi-channel ROSA is described
and shown in greater detail. The embodiment shown in FIG. 3 is one
example of the optical transceiver 200 of FIG. 2 implemented in a
small form-factor. For example, the optical transceiver 300 may
implement the QSFP+ specification. The optical transceiver 300
includes the transceiver housing 202, a multi-channel TOSA 302 in
one region of the housing 202, and a multi-channel ROSA 230 located
in another region of the housing 202. As shown, the TO can laser
package 304c of the multi-channel TOSA 302 directly contacts a
surface of the ROSA 230. The multi-channel TOSA 302 is electrically
connected to transmit flexible printed circuits (FPCs) 304 and
optically coupled to the LC connector port 212 at an end of the
housing 202. The multi-channel ROSA 230 is electrically connected
to a receive flexible printed circuit (FPC) 309 and optically
coupled to the LC connector port 212 at the end of the housing
202.
[0027] The multi-channel TOSA 302 includes TO can laser packages
304a, 304b, 304c, and 304d, with each containing optical components
such as a laser diode. The TO can laser packages can provide, for
example, output power from 1.85 mW to 2 W, although other output
power is within the scope of this disclosure. The TO can laser
packages may provide a broad spectrum of channel wavelengths, or
configured to provide a relatively narrow spectrum of channel
wavelengths such as a single channel wavelength. In some cases, the
TO can laser packages provide center wavelengths 375 nm to 1650 nm,
for example. In an embodiment, the TO can laser packages are O3.8
mm, O5.6 mm, or O9 mm TO cans, although other configurations are
also within the scope of this disclosure. For instance, the TO can
laser packages can include O9.5 mm and TO-46 cans.
[0028] One specific example of a TO can laser package 700 is shown
in FIG. 7. As shown, the TO can laser package 700 includes a
housing 702, connector pins 704, and a header 706 with a laser
diode 708. The connector pins 704 couple to the transmit FPC 304,
and the multi-channel TOSA 302 optically couples an associated
channel wavelength of the laser diode 708 to the transmit optical
fiber 222 of the external fibers 224 (FIG. 2) via collimating
lenses, filters, and other optics such as a focusing lens, as
discussed in greater detail below with reference to FIG. 4B.
[0029] Returning to FIG. 3, the multi-channel TOSA 302 includes TO
can laser packages 304a-304d fixedly attached in a staggered
manner, with TO can laser package 304c being disposed on opposing
sidewall to that of TO can laser packages 304a and 304b, as
discussed in greater detail below.
[0030] Referring to FIG. 4A, one embodiment of a multi-channel TOSA
302 for use in the optical transceiver module shown in FIG. 3 is
shown in greater detail. As shown, the multi-channel TOSA 302
includes a housing 202 with first and second sidewalls 308 and 310,
respectively, positioned on opposite sides of the housing 202 and
extending generally in parallel along a first major axis 303 from a
first end 326 to a second end 327, and forming a compartment
defined by an inner surface within the housing 202. The first
sidewall 308 includes at least first and second sidewall openings
404a and 404b (also shown with additional detail in FIG. 5) and the
second sidewall 310 includes at least a third sidewall opening 404c
being positioned generally at a midpoint 307 located between the
sidewall openings 404a and 404b of the first sidewall 308. The
multi-channel TOSA 302 includes first and second TO can laser
packages 304a and 304b fixedly attached to the first and second
openings 404a and 404b of the first sidewall 308, respectively, and
a third TO can laser package 304c fixedly attached to the third
sidewall opening 404c opposing the first and second TO can laser
packages 304a and 304b. The housing 202 further includes an end
sidewall 312 at the first end 326 and adjoining the first and
second sidewalls 308 and 310, the end sidewall 312 including a
fourth sidewall opening 404d and a fourth TO can laser package 304d
fixedly attached thereto.
[0031] As shown, the dimension 306 includes a distance of at least
about 3 mm along the surface of the first sidewall 308 between
adjacent TO can laser packages 304a and 304b. In some cases,
dimension 306 includes a length of 2 mm to 5 mm, for example. As
will be appreciated in light of this disclosure, dimension 306
departs from other TOSA approaches, such as discussed above with
regard to FIG. 1, that have a minimal spacing between TO can laser
packages. This increased dimension 306 advantageously allows laser
welds to be formed without the cost and complexity normally
associated with having tight tolerances between laser packages. For
example, and as shown in FIG. 4A, angle .theta. is generally
30.degree. relative to the housing 202. This means that laser
welding systems can perform welding at multiple angles from, for
example, 30.degree. tot 36.degree., for example. In other cases,
the angle .theta. allows laser welding systems to weld at less than
30.degree..
[0032] Referring to FIG. 4B, there is a cross-sectional view of the
multi-channel TOSA 302 of FIG. 3. As shown, the housing 202 also
forms an internal cavity 316, or compartment, that defines a light
path 322 that extends through filters 318a, 318b and 318c,
respectively, before encountering focusing lens 320. The filters
318a-318c are positioned on filter holders 319a, 319b, and 319c,
respectively. An optical coupling receptacle 324 extends from the
second end 327 for optically coupling the light of TO can laser
packages 304a-304d to the transmit optical fiber 222. Thus the
filters 318a-318d, the lens 320, the optical coupling receptacle
324 are generally aligned or positioned along a longitudinal axis
provided by the light path 322. This combination of filters may be
accurately described as multiplexing optics and can provide coarse
wavelength division multiplexing (CWDM) in an optical signal.
Multiplexing different channel wavelengths using this configuration
will now be discussed in the context of a four (4) channel TOSA
configuration, such as shown in FIG. 4B.
[0033] Each of the TO can laser packages 304a-304d can be
associated with different channel wavelengths. For example, the
channel wavelengths (.lamda.1, .lamda.2, .lamda.3, .lamda.4)
associated with TO can laser packages 304a-304d may be 1290 nm,
1330 nm, 1310 nm, and 1270 nm, respectively. To multiplex these
different channel wavelengths into a signal optically coupled to
transmit optical fiber 222, the housing includes TO can laser
package 304d configured to direct light coaxially along light path
322 into the compartment 316. In turn, the filter 318a positioned
adjacent the TO can laser package 304d can provide
wavelength-dependent transmission such that only the channel
wavelength .lamda.1, associated with the TO can laser package 304d,
pass through filter 318a. The filter 318a may also provide
wavelength-dependent reflectivity such that only channel wavelength
.lamda.2 is reflected therefrom. At this point, the light along
light path 322 includes, essentially, channel wavelengths .lamda.1
and .lamda.2. After those channel wavelengths pass through filter
318c, they converge with wavelength .lamda.3, which is provided by
the filter 318c reflecting only channel wavelength .lamda.3 from
the light directed by TO laser package 304c. At this point the
light along light path 322 now includes, essentially, channel
wavelengths .lamda.1, .lamda.2 and .lamda.3. After those channel
wavelengths pass through filter 318b, they converge with channel
wavelength .lamda.4, which is provided by the filter 318b
reflecting only channel wavelength .lamda.4 from the light directed
by TO laser package 304b. As shown, collimating lenses 305a-305d
collimate light emitted by each TO can laser package. Thus at
focusing lens 320, the resulting optical signal includes multiple
different multiplexed channel wavelengths (e.g., .lamda.1,
.lamda.2, .lamda.3, .lamda.4) and is optically coupled to the
transmit optical fiber 222.
[0034] As should be appreciated, the multi-channel TOSA 302 may
include additional channels and is not necessarily limited to the
four (4) shown in FIG. 4B. That is, additional TO can laser
packages may be disposed along the sidewalls of housing 202. For
instance, the first sidewall 308 may include 3 or more TO can laser
packages. Each of those TO can laser packages may be disposed with
spacing similar to the embodiment shown in FIG. 4B. On the opposing
sidewall, such as second sidewall 310, TO can laser packages may be
fixedly attached such that they are disposed generally coextensive
or otherwise overlapping with the area between each of the TO can
laser packages of the first sidewall 308. This staggered/opposing
arrangement may be repeated for N number of optical channels,
depending on a desired configuration.
[0035] Moreover, it should be appreciated in light of this
disclosure that placement of the TO can laser packages are not
necessarily limited to the embodiment shown. For example, TO can
laser package 304c may be fixedly attached to a sidewall that is
perpendicular (or at a right angle) to the TO can laser packages
304a and 304b.
[0036] Referring now to FIG. 5, there is an exploded view of the
multi-channel TOSA 302, in accordance with an embodiment of the
present disclosure. As shown, each of the TO can laser packages
304a-304d include an associated welding ring 402a, 402b, 402c, and
402d, respectively. These welding rings 402a-402d allow the TO can
laser packages 304a-304d to be placed over and fixedly attached to
sidewall openings 404a, 404b, 404c and 404d, respectively. As
previously discussed, laser welding is one approach that is
particularly well suited for ensuring optical efficiency (power)
and reliable operation over a lifetime of the multi-channel TOSA
302.
[0037] Note that an outer surface of the filter holder 319b is
substantially flat, and co-planar with an outer surface of the
first sidewall 308. This advantageously provides a generally flat
area that does not otherwise obstruct access when attaching TO can
laser packages 304a and 304b during manufacturing. FIG. 6A further
illustrates how filter holder 319c resides between TO can laser
packages 304a and 304b, but is coplanar or otherwise flat against
the first sidewall 308. On the other hand, FIG. 6B illustrates how
filter holders 319a and 319b are generally flat and also do not
obstruct access to the area around TO can laser package 304c along
the second sidewall 310. As shown in FIG. 6A and 6B, the
multi-channel TOSA 302 may have a relatively small size. In some
embodiments, the long axis of the housing may be 15 mm, or
less.
[0038] The multi-channel TOSA 302 may be formed as one piece or as
multiple pieces attached together. Although the illustrated
embodiment shows the multi-channel TOSA 302 with a particular
shape, other shapes and configurations are also possible. In other
embodiments, for example, the housing 202 may be generally
cylindrical.
[0039] The increased distance between the TO can laser packages
304a-304d advantageously provides for increased tolerances when
fixedly attaching the same to sidewall openings 404a-404d of the
housing 202. This increased area allows for a laser welding system
to have a wide-range of angles in which to generate welds, and
thus, increase yield and reliability of the multi-channel TOSA 302
because of reduced error rates and faster time between establishing
initial laser welds and optimizing optical efficiency through laser
hammering. In addition, an increased surface area between TO can
laser packages improves transfer or heat conduction, and thus,
facilitates more effective heat dissipation than other approaches
to TOSA packages (e.g., such as shown in FIG. 1).
Further Example Embodiments
[0040] In accordance with one aspect of the present disclosure, a
transmitter optical subassembly (TOSA) including a plurality of
transistor outline (TO) can laser packages is disclosed. The TOSA
may comprise a housing including at least a first and second
sidewall on opposite sides of the housing and extending along a
first major axis from a first end to a second end, and forming a
compartment defined by an inner surface therein, the first sidewall
including at least first and second sidewall openings, the second
sidewall including at least a third sidewall opening being
positioned generally at a midpoint between the first and second
sidewall openings, and at least first and second TO can laser
packages fixedly attached to the first and second sidewall opening
of the first sidewall, respectively, and a third TO can laser
package fixedly attached to the third sidewall opening and opposing
the first and second TO can laser packages.
[0041] In one aspect, the housing may further include a third
sidewall at the first end and adjoining the first and second
sidewall, the third sidewall including a fourth sidewall opening
and a fourth TO can laser package fixedly attached thereto.
[0042] In one aspect, the TOSA may comprise a plurality of welding
rings, wherein the plurality of TO can laser packages are fixedly
attached to respective sidewalls of the housing by the plurality of
welding rings via laser welds.
[0043] In one aspect, the compartment may define a light path, the
light path extending from the first end to at least the second
end.
[0044] In one aspect, each of the plurality of TO can laser
packages may include a laser diode optically aligned to direct
light into the compartment.
[0045] In one aspect, the TOSA may further comprise filters aligned
with the TO can laser packages to pass and reflect laser light at
associated channel wavelengths.
[0046] In one aspect, each filter may include an associated filter
holder, each of the filter holders being fixedly attached to a
sidewall of the housing and providing a substantially flat surface
between adjacent TO can laser packages along an outer edge of the
housing.
[0047] In one aspect, the compartment may include a focusing lens
aligned with a light path at the second end of the housing.
[0048] In one aspect, the first and second TO can laser packages
may be greater than 1 mm apart.
[0049] In one aspect, the second end may include an optical
coupling receptacle configured to optically couple a signal having
multiple different channel wavelengths to a transmit optical
fiber.
[0050] In accordance with another aspect of the present disclosure,
an optical transceiver module is disclosed. The optical transceiver
may comprise a transceiver housing, a transmitter optical
subassembly (TOSA) having a plurality of transistor outline (TO)
can laser packages fixedly attached thereto and located in the
transceiver housing for transmitting optical signals at different
channel wavelengths, the TOSA comprising a housing including at
least a first and second sidewall on opposite sides of the housing
and extending along a first major axis from a first end to a second
end, and forming a compartment defined by an inner surface therein,
the first sidewall including at least first and second sidewall
openings, the second sidewall including at least a third sidewall
opening being positioned generally at a midpoint between the first
and second sidewall openings, and at least first and second
transistor outline TO can laser packages fixedly attached to the
first and second sidewall opening of the first sidewall,
respectively, and a third TO can laser package fixedly attached to
the third sidewall opening and opposing the first and second TO can
laser packages, a multi-channel receiver optical assembly (ROSA)
located in the transceiver housing for receiving optical signals at
different channel wavelengths.
[0051] In one aspect, the optical transceiver may further comprise
a transmit connecting circuit electrically connected to the TOSA,
and a receive connecting circuit electrically connected to the
ROSA.
[0052] In one aspect, the TOSA may further comprise filters within
the compartment configured to provide a multiplexed optical signal
having multiple different wavelengths.
[0053] In one aspect, the TOSA may further comprise a third
sidewall at the first end and adjoining the first and second
sidewall, the third sidewall including a fourth sidewall opening
and a fourth TO can laser package fixedly attached thereto.
[0054] In one aspect, each of the first, second, third and fourth
TO can laser packages may be associated with a channel wavelength
of 1290 nm, 1330 nm, 1310 nm, and 1270 nm, respectively.
[0055] In one aspect, the TOSA further may comprise a plurality of
welding rings, wherein each of the plurality of TO can laser
packages are fixedly attached to respective sidewalls of the TOSA
housing by the plurality of welding rings via laser welds.
[0056] In one aspect, the transceiver may be a Quad Small
Form-factor Pluggable (QSFP) transceiver module and the TOSA is
configured to transmit at four different channel wavelengths at
transmission rates of at least about 10 Gbps per channel and
transmission distances of 2 km to at least about 10 km.
[0057] In one aspect, the third TO can laser package may directly
contact a surface of the ROSA.
[0058] In one aspect, the first and second TO can laser packages of
the TOSA may be greater than 1 mm apart.
[0059] In one aspect, the second end of the TOSA may include an
optical coupling receptacle configured to optically couple a signal
having multiple different channel wavelengths to a transmit optical
fiber.
[0060] While the principles of the disclosure have been described
herein, it is to be understood by those skilled in the art that
this description is made only by way of example and not as a
limitation as to the scope of the disclosure. Other embodiments are
contemplated within the scope of the present disclosure in addition
to the exemplary embodiments shown and described herein.
Modifications and substitutions by one of ordinary skill in the art
are considered to be within the scope of the present disclosure,
which is not to be limited except by the following claims.
* * * * *