TECHNIQUES FOR REDUCING THE FOOTPRINT OF A MULTI-CHANNEL TRANSMITTER OPTICAL SUBASSEMBLY (TOSA) WITHIN AN OPTICAL TRANSCEIVER HOUSING

In accordance with an embodiment, a transmitter optical subassembly (TOSA) having one or more recessed mounting regions is disclosed in order to decrease the overall footprint of the TOSA within an optical transceiver housing. The TOSA includes a housing having at least a first sidewall and a second sidewall disposed on opposite sides of the housing relative to each other. The housing further includes a first step portion defined by the first sidewall and a first recessed mounting region extending from about the first step portion along the longitudinal axis towards the second end. The first recessed mounting region is defined by an external surface of the first sidewall that is offset from a surface defining the first step portion by a first offset distance. The first recessed mounting region includes at least one sidewall opening to couple to optical component assemblies.

TECHNICAL FIELD

The present disclosure relates generally to optical subassemblies, and more particularly, to a transmitter optical subassembly (TOSA) housing having a stepped-profile along one or more sidewalls to provide a recessed mounting region to couple to optical assemblies, such as laser diode assemblies, and limit the overall footprint of the TOSA within an optical transceiver housing.

BACKGROUND INFORMATION

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.

DETAILED DESCRIPTION

Some small form-factor (SFF) optical transceiver housings, such as SFF pluggable (SFFP) transceiver housings, include dimensions in the tens of millimeters or less, for example, and thus provide relatively constrained housings for associated transmitter optical subassemblies (TOSAs) and receiver optical subassemblies (ROSAs). Subassemblies designed to fit within such constrained housings can complicate manufacturing processes and present non-trivial issues. For example, TOSAs such as the TOSA shown inFIG. 1A, may include a relatively small dimension106between adjacent TO can laser packages (or assemblies)104band104c. As shown, the multi-channel TOSA100includes four (4) TO can laser packages104a-104d, three (3) of which are arranged coupled to a first sidewall120of the housing102. However, post attachment alignment of TO can laser packages104a-cusing, for instance, a laser welding system may be complicated, error-prone, and time-consuming due to the relatively limited range of available approach angles a, which arise from the constraints imposed by the dimension106. Therefore, in some TOSAs it may be desirable to have one or more optical assemblies coupled to the TOSA housing in an opposing configuration, such as shown in the example embodiment ofFIG. 1B, which will be discussed in greater detail below. An example TOSA with an opposing TO can laser package configuration is also discussed in detail in co-pending '993 Application.

While such an opposing TO can configuration may provide various advantages, e.g., providing additional space for post-attachment alignment of the optical assemblies coupled to the TOSA housing via welding, it may also result in the overall footprint of the TOSA being increased relative to a TOSA having a non-opposing configuration, such as shown in the example TOSA100ofFIG. 1A. For example, as shown in the SFFP transceiver housing ofFIG. 3, a transmitter optical subassembly (TOSA)302is disposed in a first region of a cavity defined by the SFF housing202, and a receiver optical subassembly (ROSA)230is disposed in a second region of the cavity defined by the SFF housing202. The opposing configuration of the TOSA302, and more particularly, the pins of the TO can laser package304cextend toward and make contact with a surface of the ROSA230. Such contact may result in operational interference between the TOSA302and the ROSA230, e.g., resulting in an electrical short or RF interference, and may also further complicate attachment of associated circuitry to the pins of the TO laser package304c,e.g., a flexible printed circuit board. Even in configurations without an opposing TO can configuration, TOSAs and other subassemblies may include footprints that complicate the design and manufacture of optical transceiver housings.

Thus, in accordance with an embodiment of the present disclosure, a TOSA having a housing with a stepped-profile along at least one sidewall to reduce the overall footprint of a TOSA is provided. In an embodiment, the TOSA includes a housing having a plurality of sidewalls, wherein a first sidewall of the plurality of sidewalls defines first and second step portions, and a first recessed mounting region disposed there between. The first and second step portions may also be described as shoulder portions. The first recessed mounting region includes at least a first and second sidewall opening for receiving and coupling to an optical assembly, such as a TO can laser assembly, a filter assembly, or a mirror assembly, just to name a few. A second sidewall of the plurality of sidewalls of the housing may also define third and fourth step portions and a second recessed mounting region disposed there between. The second sidewall may be disposed opposite the first sidewall and, by extension, the second recessed mounting region may oppose the first recessed mounting region. The second recessed mounting region includes at least a third sidewall opening for receiving an optical assembly. The third sidewall opening is positioned opposite the first and second sidewall openings, and is generally located at a mid-point between the first and second sidewall openings. As such, the optical assemblies are positioned within a respective recessed mounting region in a staggered and opposing configuration. Accordingly, the TOSA housing can include a reduced footprint along at least one dimension measured from an outer surface of the first recessed region to an outer surface of the second recessed region. Although various aspects and embodiments discussed herein include a TOSA housing having recessed regions disposed in an opposing fashion, this disclosure is not necessarily limited in this regard. For example, the TOSA housing may include recessed regions on any number of sidewalls including a single sidewall, multiple sidewalls, and multiple opposing sidewalls, depending on a desired configuration.

In any event, the inclusion of one or more recessed mounting regions in the TOSA housing advantageously allows for the overall footprint of the TOSA to be reduced relative to the extent of the recess. As will be discussed in further detail below, step portions associated with the one or more recessed mounting regions may also provide a suitable mounting point for optical assemblies to mount to sidewalls that adjoin the one or more sidewalls that provide recessed mounting regions. For instance, and as shown by the TOSA housing ofFIG. 4C, the step portions450and454adjacent the recessed mounting regions406and407, respectively, may advantageously allow for the fourth TO can laser assembly304dto couple to the housing301of the TOSA302. Therefore, although the staggered and opposing configuration may increase the overall footprint of the TOSA, e.g., by virtue of pins from TO can laser assemblies extending out from multiple sidewalls, the inclusion of one or more recessed mounting regions minimizes or otherwise reduces the magnitude of the increase in the overall footprint of the TOSA. Moreover, a TOSA housing having one or more recessed mounting regions, as variously disclosed herein, allows the same to have any number of TO can placement configurations, e.g., an opposing placement as shown inFIG. 1B, a non-opposing placement as shown inFIG. 1A, and so on, while comporting with the physical constraints of a particular optical transceiver housing.

While the present disclosure refers specifically to a TOSA including TO can laser packages, such a configuration is not intended to limit the present disclosure. A TO can laser package represents one suitable type of optical assembly that can be used herein and other optical assemblies including, for example, one or more, filters, mirrors, laser diodes, lenses, diffusers, polarizers, prisms, beam splitters, diffraction gratings, and other similar assemblies that may undesirably increase the footprint of an optical subassembly when coupled thereto may also be used. Furthermore, while the present disclosure primarily refers to a TOSA, this disclosure is equally applicable to, for example, a receiver optical subassembly (ROSA).

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 toFIG. 2, there is an optical transceiver200consistent with embodiments of the present disclosure. In more detail, the optical transceiver200transmits and receives four (4) channels using four different channel wavelengths (λ1, λ2, λ3, λ4) and may be capable of transmission rates of at least about 10 Gbps per channel. In one example, the channel wavelengths λ1, λ2, λ3, λ4may be 1270 nm, 1290 nm, 1080 nm, and 1330 nm, respectively. The optical transceiver200may also be capable of transmission distances of 2 km to at least about 10 km. The optical transceiver200may be used, for example, in Internet data center applications or fiber to the home (FTTH) applications. In an embodiment, the optical transceiver200implements the specification SFF-8436 titled “QSFP+ 10 Gbs 4× PLUGGABLE TRANSCEIVER Rev 4.8” (hereinafter QSFP+), published on Oct. 31, 2013, by the Electronic Industries Alliance (EIA).

This embodiment of the optical transceiver200includes a multi-channel TOSA302for transmitting optical signals on different channel wavelengths and a multi-channel receiver optical subassembly (ROSA)230for receiving optical signals on different channel wavelengths. The multi-channel TOSA302and the multi-channel ROSA230are located in a transceiver housing202. A transmit connecting circuit204and a receive connecting circuit208provide electrical connections to the multi-channel TOSA302and the multi-channel ROSA230, respectively, within the housing202and communicate with external systems via data bus203. In some cases, data bus203is a 38-pin connector that comports with physical connector QSFP standards and data communication protocols.

In any event, the transmit connecting circuit204is electrically connected to the electronic components (e.g., TO can laser packages) in the multi-channel TOSA302, and the receive connecting circuit208is electrically connected to the electronic components (e.g., the photodiode packages) in the multi-channel ROSA230. The transmit connecting circuit204and the receive connecting circuit208include at least conductive paths to provide electrical connections and may also include additional circuitry. The multi-channel TOSA302transmits and multiplexes multiple channel wavelengths and is coupled to an optical interface port212. The optical interface port212may comprise an LC connector receptacle, although other connector types are also within the scope of this disclosure. For example, the optical interface port212may comprise a multi-fiber push on (MPO) connector receptacle.

In cases where the optical interface port212comprises a duplex, or bi-directional, LC receptacle, the LC connector receptacle provides optical connections to the multi-channel TOSA302, and provides optical connections to the multi-channel ROSA230. The LC connector receptacle may be configured to receive and be coupled to a mating LC connector214such that the transmit optical fiber222of the external fibers224optically couples to the multi-channel TOSA302, and the receive optical fiber217of the external fibers224optically couples to the multi-channel ROSA230.

The multi-channel TOSA302includes 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 fiber222. In particular, the lasers in the multi-channel TOSA302convert electrical data signals (TX_D1to TX_D4) received via the transmit connecting circuit204into modulated optical signals transmitted over the transmit optical fiber222. The lasers may include, for example, distributed feedback (DFB) lasers with diffraction gratings. The multi-channel TOSA302may also include monitor photodiodes for monitoring the light emitted by the lasers. The multi-channel TOSA302may 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 ROSA230includes, for example, photodiodes, mirrors and filters that can de-multiplex different channel wavelengths in a received optical signal. The multi-channel ROSA230can detect, amplify, and convert such optical signals received from the external optical fibers224, and can provide the converted optical signals as electrical data signals (RX_D1to RX_D4) that are output via the receive connecting circuit208. This embodiment of the optical transceiver200includes 4 channels and may be configured for coarse wavelength division multiplexing (CWDM), although other numbers of channels are within the scope of this disclosure.

Referring toFIG. 3, an example small form-factor (SFF) pluggable optical transceiver300with a multi-channel TOSA including TO can laser packages and multi-channel ROSA is described and shown in greater detail. The embodiment shown inFIG. 3is one example of the optical transceiver200ofFIG. 2implemented in a small form-factor. For example, the optical transceiver300may implement the QSFP+ specification. The optical transceiver300includes the transceiver housing202, a multi-channel TOSA302in one region of the housing202, and a multi-channel ROSA230located in another region of the housing202. As shown, the TO can laser package304cof the multi-channel TOSA302directly contacts a surface of the ROSA230. The multi-channel TOSA302is electrically connected to transmit flexible printed circuits (FPCs)311and optically coupled to the LC connector port212at an end of the housing202. The multi-channel ROSA230is electrically connected to a receive flexible printed circuit (FPC)309and optically coupled to the LC connector port212at the end of the housing202.

The multi-channel TOSA302includes TO can laser packages304a,304b,304c,and304d,with each containing optical components (or optical component assemblies) such as a laser diode. The TO can laser packages304a-304dcan 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 packages304a-304dmay 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 packages304a-304dprovide center wavelengths 375 nm to 1650 nm, for example. In an embodiment, the TO can laser packages304a-304dare 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 packages304a-304dcan include Ø9.5 mm and TO-46 cans.

The multi-channel TOSA302includes TO can laser packages304a-304dwithin a recessed mounting region and coupled in a staggered manner, with TO can laser package304cbeing disposed on an opposing sidewall to that of TO can laser packages304aand304b,as discussed in greater detail below. The multi-channel TOSA302may further include one or more recessed mounting regions, as discussed in greater detail below, that allow the multi-channel TOSA302to have a relatively reduced overall footprint within an optical transceiver housing.

Referring toFIG. 4A, with additional reference toFIG. 3, a cross-sectional view of an example housing301for the multi-channel TOSA302ofFIG. 3is shown in accordance with an embodiment of the present disclosure. As shown, the housing301includes first and second sidewalls308and310, respectively, positioned on opposite sides of the housing301and extending generally in parallel along a longitudinal axis303from a first end326to a second end327. The housing301further provides a cavity (or compartment)316. The first sidewall308includes at least first and second sidewall openings404aand404b,and the second sidewall310includes at least a third sidewall opening404cbeing positioned generally at a midpoint axis307of the housing301. The midpoint axis307may extend from the first sidewall308to the second sidewall310and between the first and second sidewall openings404aand404bof the first sidewall308. In some instances, the midpoint axis307may be located at a center of the housing301. The first and second sidewall openings404aand404btransition from an external surface408of the first sidewall308and into the cavity316. The third sidewall opening404ctransitions from an external surface409of the second sidewall310and into the cavity316.

Referring toFIG. 4B, with additional reference toFIG. 4A, a side plan view of the housing301ofFIG. 4Aincludes hidden lines generally illustrating various internal structural features of the housing301, in accordance with an embodiment of the present disclosure. As shown, a first recessed mounting region406is defined by the external surface408of the first sidewall308and extends between the first end326and second end327of the housing301. As further shown, the first end326may define a first step portion450and the second end327may define a second step portion452. The first and second step portion450and452include a respective external surface414and416coupled to a respective one or more sidewalls423and424extending in an upward direction away from the external surface408of the first sidewall308. The respective one or more sidewalls423and424may be adjacent to a portion of the external surface408that defines the first recessed mounting region406. Accordingly, the first recessed region406extends between the first step portion450and the second step portion452and may include the first and second sidewall openings404aand404b.

The housing301may comprise a metal, an alloy, a plastic, or any other suitably rigid material. The housing301may comprise multiple segments or be formed from a single segment. In some cases, the step portions, such as the step portions450,452,454, and456, are integrally formed with the housing301. For example, the step portions450and452may be formed by casting, milling, or other similar approaches. In other cases, the step portions450,452,454, and456may be separate segments added to the housing301using, for example, press-fitting, welding, adhesives, or other approaches to fixation.

As also shown, the external surface (or surface)414of the first step portion450is offset from the external surface408of the first recessed mounting region406by a first offset distance412. Likewise, the external surface (or surface)416of the second step portion452is offset from the external surface408of the first recessed mounting region by a second offset distance418. The first offset distance412and the second offset distance418may measure substantially the same distance, or may measure different distances depending on a desired configuration. For example, the first offset distance412and/or the second offset distance418may measure 0.15 millimeters (mm), 0.3 mm, 0.45 mm, 0.6 mm, 1.0 mm, 1.5 mm, any range of measurements there between, or any other desired measurement. The first and second offset distances412and418of the first recessed mounting region406may result in a recessed mounting region thickness420being less than an overall step thickness422. Stated differently, the reduction in thickness measured at420may be directly proportional to the offset distances412and418that, in a general sense, counter-sink the first recessed mounting region406into the housing301. The first recessed mounting region406may be configured to couple optical components such as TO can laser assemblies to the first and second openings404aand404b. The first recessed mounting region406may be further configured to couple to other optical components by way of additional openings, such as the opening460ofFIG. 4A, for example.

As further shown, the housing301, and more particularly the second sidewall310, may define the third and fourth step portions (or step regions)454and456and a second recessed mounting region407extending there between. The second recessed mounting region407may be defined by the external surface409of the second sidewall310that is offset from at least one of an external surface442or an external surface444of the third and fourth step regions454and456by a third offset distance441and/or fourth offset distance443, respectively. The second recessed mounting region407may include the third sidewall opening404c.Further discussion of the step portions454and456and second recessed mounting region407will generally be omitted herein for the sake of brevity because the step portions454and456and second recessed mounting region407may be configured to be substantially similar to the step portions450and452and the first recessed region406. To this end, the third and fourth offset distances441and443may measure substantially the same as offset distances412and418, although other embodiments are within the scope of this disclosure. For instance, the third and fourth offset distances441and443may measure substantially equal to each other, but may also measure less than or greater than the offset distances412and418. In some cases, the first, second, third, and fourth offset distances412,418,441, and443may measure substantially the same. Accordingly, in some embodiments, each of the first and second recessed mounting regions406and407may include substantially the same configuration such that the housing301is substantially symmetric about the longitudinal axis303and/or about the midpoint axis307. However, such a symmetrical recessed mounting configuration is not necessarily required and each recessed mounting region406and407may include different configurations. Further, as shown collectively in the example embodiments ofFIGS. 4B and 4C, the first offset distance412, the second offset distance418, the third offset distance441, and/or the fourth offset distance443may measure equal to a thickness of the one or more welding rings402a-402d.The first and second recessed mounting regions406and407are shown with a generally planar (or flat) configuration. However, the first and second recessed mounting regions406and407may be configured with non-planar surfaces and this disclosure should not be limited in this regard.

Turning toFIG. 4C, with additional reference toFIGS. 4A and 4B, first and second TO can laser packages304aand304bare shown coupled to the first and second sidewall openings404aand404bof the first sidewall308, respectively, and a third TO can laser package304cis coupled to the third sidewall opening404c,with the third sidewall opening404copposing the first and second TO can laser packages304aand304b.As shown, the first recessed mounting region406allows the TO can laser packages304aand304bto couple to the housing301at a position below the surfaces414and416of the first and second step portions450and452, respectively. Likewise, the second recessed mounting region407allows the third TO can laser assembly304cto couple to the housing301in a similar fashion, e.g., below surfaces defining the third and fourth step portions454and456. Thus, the overall width434of the TOSA302relative to, for example, the overall width108of the TOSA110ofFIG. 1B, may be reduced. To this end, the resulting overall width434of the TOSA302may advantageously reduce the overall footprint of the same within a transceiver housing, such as the SFFP transceiver housing202ofFIG. 3.

Continuing withFIG. 4C, the first recessed mounting region406may have a length432measured between the first and second step portions450and452. The length432of the first recessed mounting region406may be such that the first and second openings404aand404bof the first sidewall308can receive TO can laser packages304aand304b.For example, the length432of the first recessed mounting region406may be based, at least in part, on a dimension306between adjacent TO can laser packages304aand304b.In some cases, the dimension306is at least about 3 mm, although other embodiments are within the scope of this disclosure. In other cases, dimension306is between 2 mm and 5 mm, for example. The dimension306provides component spacing greater than that of other approaches to TOSAs, such as the TOSA100shown inFIG. 1A. This increased dimension306advantageously allows laser welds to be formed without the cost and complexity normally associated with having tight tolerances between laser packages. For instance, an approach angle θ for the laser welding system may be within the range of 30° to 36°. In other cases, the range of the approach angles θ may include angles less than 30°. Therefore, the range of the approach angles θ may be greater for the TOSA302than for other approaches, such as the TOSA100ofFIG. 1A.

AlthoughFIG. 4Cshows the second recessed mounting region407having a length substantially equal to the length432of the first recessed mounting region406, other embodiments are within the scope of this disclosure. For example, the length of the second recessed mounting region407may be greater than or less than the length432.

Continuing withFIG. 4C, with additional reference toFIG. 4B, the fourth TO can laser package304dcan be coupled to the housing301at a third sidewall312, with the third sidewall312adjoining the first and second sidewalls308and310. The third sidewall312includes a fourth sidewall opening404d.The housing301may further include an optical coupling receptacle324coupled to a fourth sidewall313by way of a fifth sidewall opening404e,the fifth sidewall opening404ebeing opposite the fourth sidewall opening404d.

As shown, the first and third step portions450and454advantageously provide structural support for the purposes of coupling to the fourth TO can laser package304d.For example, the overall step thickness422(FIG. 4B) may be of sufficient size such that the fourth TO can laser package304dcan be coupled to the housing301by way of the fourth sidewall opening404d.Similarly, the second and fourth step portions452and456may provide the housing301with a thickness sufficient to support the coupling of the optical coupling receptacle324to the housing301by way of the fifth sidewall opening404e.Stated differently, step portions450,452,454, and456of the housing301may be sized with dimensions that support attachment of laser packages/optical components at ends of the housing301. To this end, the dimensions of a particular optical component/assembly may determine the particular overall step thickness422of the optical housing.

Referring toFIG. 4D, there is a cross-sectional view of the multi-channel TOSA302ofFIG. 3in accordance with an embodiment. As shown, the housing301also forms the cavity316, or compartment, that defines a light path322that extends through filters318a,318b,and318c,respectively, before encountering a focusing lens320. The filters318a-318care positioned on filter holders319a,319b,and319c,respectively. The optical coupling receptacle324extends from the second end327for optically coupling the light of TO can laser packages304a-304dto the transmit optical fiber222. Thus, the filters318a-318c,the lens320, and the optical coupling receptacle324are generally aligned or positioned along a longitudinal axis provided by the light path322. 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 inFIG. 4C.

Each of the TO can laser packages304a-304dcan be associated with different channel wavelengths. For example, the channel wavelengths (λ1, λ2, λ3, λ4) associated with TO can laser packages304a-304dmay 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 fiber222, the housing includes TO can laser package304dconfigured to direct light coaxially along light path322into the cavity (or compartment)316. In turn, the filter318apositioned adjacent the TO can laser package304dcan provide wavelength-dependent transmission such that only the channel wavelength λ1, associated with the TO can laser package304d,passes through filter318a.The filter318amay also provide wavelength-dependent reflectivity such that only channel wavelength λ2is reflected therefrom. At this point, the light along light path322includes, essentially, channel wavelengths λ1and λ2. After those channel wavelengths pass through filter318c,they converge with wavelength λ3, which is provided by the filter318creflecting only channel wavelength λ3from the light directed by TO laser package304c.At this point the light along light path322now includes, essentially, channel wavelengths λ1, λ2, and λ3. After those channel wavelengths pass through filter318b,they converge with channel wavelength λ4, which is provided by the filter318breflecting only channel wavelength λ4from the light directed by TO laser package304b.As shown, collimating lenses305a-305dcollimate light emitted by each TO can laser package. Thus, at focusing lens320, the resulting optical signal includes multiple different multiplexed channel wavelengths (e.g., λ1, λ2, λ3, λ4) and is optically coupled to the transmit optical fiber222.

The multi-channel TOSA302may include additional channels and is not necessarily limited to the four (4) shown inFIG. 4D. That is, additional TO can laser packages may be disposed along the sidewalls of housing301. For instance, the first sidewall308may 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 inFIG. 4D. On the opposing sidewall, such as second sidewall310, TO can laser packages may be coupled such that they are disposed generally coextensive or otherwise overlapping with the area between each of the TO can laser packages of the first sidewall308. This staggered/opposing arrangement may be repeated for N number of optical channels, depending on a desired configuration.

Moreover, the placement of the TO can laser packages are not necessarily limited to the embodiment shown. For example, TO can laser package304cmay be coupled to a sidewall that is perpendicular (or at a right angle) to the TO can laser packages304aand304b.

Referring now toFIG. 5, there is an exploded view of the multi-channel TOSA302, in accordance with an embodiment of the present disclosure. As shown, each of the TO can laser packages304a-304dinclude an associated welding ring402a-402d,respectively. These welding rings402a-402dallow the TO can laser packages304a-304dto be placed over and coupled to sidewall openings404a-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 TOSA302.

Note that an outer surface of the filter holder319bis substantially flat and co-planar with an outer surface of the first sidewall308. This advantageously provides a generally flat area that does not otherwise obstruct access when attaching TO can laser packages304aand304bduring manufacturing.FIG. 6Afurther illustrates how the filter holder319cis positioned between the first and second step portions450and452and is substantially coplanar with at least a portion of the external surface408of the first sidewall308that defines the first recessed mounting region406. The filter hold319cresides between TO can laser packages304aand304b.On the other hand,FIG. 6Billustrates how filter holders319aand319bare between the third and fourth step portions454and456, are generally flat, and generally do not obstruct access to the area around TO can laser package304calong at least a portion of the external surface409of the second sidewall310that defines the second recessed region407. As shown inFIG. 6A and 6B, the multi-channel TOSA302may have a relatively small size. In some embodiments, the long axis of the housing may be 15 mm, or less.

The multi-channel TOSA302may be formed as one piece or as multiple pieces attached together. Although the illustrated embodiment shows the multi-channel TOSA302with a particular shape, other shapes and configurations are also possible. In other embodiments, for example, the housing301may be generally cylindrical.

Further Example Embodiments

In accordance with an aspect of the present disclosure a transmitter optical subassembly (TOSA) is disclosed. The TOSA including a housing including at least a first sidewall and a second sidewall disposed on opposite sides of the housing relative to each other, the first and second sidewalls extending along a longitudinal axis from a first end to a second end of the housing, wherein the housing further includes a first step portion defined by the first sidewall and disposed adjacent the first end of the housing, a first recessed mounting region disposed adjacent the first step portion, the first recessed mounting region defined by an external surface of the first sidewall that extends along the longitudinal axis towards the second end of the housing, the external surface defining the first recessed mounting region being offset from a surface defining the first step portion by a first offset distance, and wherein the first recessed mounting region includes at least a first sidewall opening, the first sidewall opening configured to couple to an optical component assembly.

In accordance with another aspect of the present disclosure an optical transceiver is disclosed. The optical transceiver 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 TOSA housing including at least a first sidewall and a second sidewall disposed on opposite sides of the TOSA housing relative to each other, the first and second sidewalls extending along a longitudinal axis from a first end to a second end of the TOSA housing, wherein the TOSA housing further includes first and second step portions defined by the first sidewall and a first recessed mounting region extending there between, the first recessed mounting region being defined by an external surface of the first sidewall that is offset from a surface defining the first step portion by a first offset distance, wherein the first recessed mounting region includes at least a first sidewall opening and a second sidewall opening, each of the first and second sidewall openings to couple to respective TO can laser packages, and at least first and second TO can laser packages coupled to the first and second sidewall openings of the first sidewall, respectively, and a multi-channel receiver optical assembly (ROSA) located in the transceiver housing for receiving optical signals at different channel wavelengths.

In accordance with yet another aspect of the present disclosure an optical transceiver is disclosed. The optical transceiver including a housing including at least a first sidewall and a second sidewall disposed on opposite sides of the housing relative to each other, the first and second sidewalls extending along a longitudinal axis from a first end to a second end of the housing and providing a cavity therebetween, wherein the housing comprises a first and second step portion defined by the first sidewall and a first recessed mounting region disposed there between, the first recessed mounting region being defined by an external surface of the first sidewall that is offset from a surface defining the first step portion by a first offset distance, wherein the first recessed mounting region includes at least a first sidewall opening and a second sidewall opening to couple to respective TO can laser packages, a third and fourth step portion defined by the second sidewall and a second recessed mounting region disposed there between, the second recessed mounting region being defined by an external surface of the second sidewall that is offset from a surface defining the third step portion by a second offset distance, wherein the second recessed mounting region includes at least one third sidewall opening to couple to respective TO can laser packages, and first, second, and third transistor outline (TO) can laser packages coupled to each of the first, second, and third sidewall openings, respectively.