Patent Application
20170063464
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.
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.
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.
These and other features and advantages will be better understood by reading the following detailed description, taken together with the drawings wherein:
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.
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,
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 θ, a laser welding system has approximately 87°±1° 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.
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
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.
Now turning to
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.
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.
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.
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.
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.
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.
Referring to
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 Ø3.8 mm, Ø5.6 mm, or Ø9 mm TO cans, although other configurations are also within the scope of this disclosure. For instance, the TO can laser packages can include Ø9.5 mm and TO-46 cans.
One specific example of a TO can laser package 700 is shown in
Returning to
Referring to
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
Referring to
Each of the TO can laser packages 304a-304d can be associated with different channel wavelengths. For example, the channel wavelengths (λ1, λ2, λ3, λ4) 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 λ1, 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 λ2 is reflected therefrom. At this point, the light along light path 322 includes, essentially, channel wavelengths λ1 and λ2. After those channel wavelengths pass through filter 318c, they converge with wavelength λ3, which is provided by the filter 318c reflecting only channel wavelength λ3 from the light directed by TO laser package 304c. At this point the light along light path 322 now includes, essentially, channel wavelengths λ1, λ2 and λ3. After those channel wavelengths pass through filter 318b, they converge with channel wavelength λ4, which is provided by the filter 318b reflecting only channel wavelength λ4 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., λ1, λ2, λ3, λ4) and is optically coupled to the transmit optical fiber 222.
As should be appreciated, the multi-channel TOSA 302 may include additional channels and is not necessarily limited to the four (4) shown in
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.
Referring now to
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.
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.
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
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.
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.
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.
In one aspect, the compartment may define a light path, the light path extending from the first end to at least the second end.
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.
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.
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.
In one aspect, the compartment may include a focusing lens aligned with a light path at the second end of the housing.
In one aspect, the first and second TO can laser packages may be greater than 1 mm apart.
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.
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.
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.
In one aspect, the TOSA may further comprise filters within the compartment configured to provide a multiplexed optical signal having multiple different wavelengths.
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.
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.
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.
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.
In one aspect, the third TO can laser package may directly contact a surface of the ROSA.
In one aspect, the first and second TO can laser packages of the TOSA may be greater than 1 mm apart.
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.
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.
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.
