Transmitter optical subassembly arrangement with vertically-mounted monitor photodiodes

The present disclosure is generally directed to a multi-channel TOSA with vertically-mounted MPDs to reduce TOSA housing dimensions and improve RF driving signal quality. In more detail, a TOSA housing consistent with the present disclosure includes at least one vertical MPD mounting surface that extends substantially transverse relative to a LD mounting surface, with the result being that a MPD coupled to the vertical MPD mounting surface gets positioned above an associated LD coupled to the LD mounting surface. The vertically-mounted MPD thus makes regions adjacent an LD that would otherwise be utilized to mount an MPD available for patterning of conductive RF traces to provide an RF driving signal to the LD. The conductive RF traces may therefore extend below the vertically-mounted MPD to a location that is proximate the LD to allow for relatively short wire bonds therebetween.

TECHNICAL FIELD

The present disclosure relates to optical communications, and more particularly, to a transmitter optical subassembly (TOSA) arrangement having vertically-mounted monitor photodiodes to reduce housing dimensions and improve radio frequency (RF) drive signal quality.

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 transmit/receive speeds in increasingly space-constrained optical transceiver modules has presented challenges, for example, with respect to thermal management, insertion loss, RF driving signal quality and manufacturing yield.

Optical transceiver modules generally include one or more transmitter optical subassemblies (TOSAs) for transmitting optical signals. TOSAs can include one or more lasers to emit one or more channel wavelengths and associated circuitry for driving the lasers. Some optical applications, such as long-distance communication, can require TOSAs to include hermetically-sealed housings with arrayed waveguide gratings, temperature control devices, laser packages and associated circuitry disposed therein to reduce loss and ensure optical performance. However, the inclusion of hermetically-sealed components increases manufacturing complexity, cost, and raises numerous non-trivial challenges within space-constrained housings.

DETAILED DESCRIPTION

As discussed above, some TOSAs can reach optical transmission distances of up to 10 km or more. Such TOSAs may be suitable for use in C form-factor pluggable (CFP), CFP2, CFP4 and quad small form-factor pluggable (QSFP) applications. In general, such TOSAs include a hermetic-sealed package (or housing) with an LC receptacle (or other suitable port) for optical coupling. The hermetic-sealed package can house laser packages, e.g., electro-absorption modulator integrated lasers (EMLs), power monitors photodiodes (PDs), thermoelectric coolers (TECs), an optical multiplexer such as an arrayed waveguide grating (AWG) for multiplexing multiple channel wavelengths, and electrical interconnects such as flexible printed circuit boards, and optical interconnects such as fiber stubs. Hermetic-sealed packages can include cavities specifically designed to house such components in a manner that optimizes the space constraints and promotes thermal communication. However, manufacturing hermetic-sealed packages with the dimensions necessary to fit the components of the light engine increases manufacturing cost and complexity.

One component in such TOSAs that can result in increased cost and complexity is monitor photodiodes (MPDs). MPDs can be used to monitor optical power of a corresponding laser diode. However, existing approaches tend to position MPDs behind, in front of, or otherwise adjacent an associated laser diode. In some cases, MPDs are mounted to the same substrate as the associated LD. For example,FIG. 10shows one example of laser arrangement1000whereby a sidewall of a TOSA housing1004supports a substrate1002(or submount), and the substrate1002and/or the surface of the TOSA housing1004supports LD1008and the MPD1006. One position utilized for registering optical power from an LD by an MPD1006is directly behind the LD1008to receive a small portion of optical power1011emitted by the LD1008backwards away from a transmit (TX) waveguide, e.g., an optical fiber. Another position includes mounting the MPD1006below or otherwise in front of the LD1008to directly receive the optical power1010emitted by the LD1008.

In either case, the TOSA housing1004must be dimensioned to accommodate the position of the MPD1006, with the result being an overall increase in housing length along dimension D. This results in two significant challenges for TOSA designs. First, the position of the MPD, e.g., behind the LD1008, can require that interconnect circuitry such as wire bonds1014that extend from the laser diode driver (LDD)1012to the LD1008must be lengthened to route over/around the MPD1006. Extending and routing the wire bonds1014in this fashion can result in time-of-flight (TOF) delays and impedance matching issues as well as worse RF performance. Second, increasing the overall length can increase the overall volume of the TOSA housing cavity and the complexity in the manufacture of the TOSA. In scenarios where hermetically-sealed housings are utilized, this can result in a significantly higher cost and time per unit to manufacture, which can ultimately reduce yield.

Thus, the present disclosure is generally directed to a multi-channel TOSA with vertically-mounted MPDs to reduce TOSA housing dimensions and improve RF driving signal quality. In more detail, a TOSA housing consistent with the present disclosure includes at least one vertical MPD mounting surface that extends substantially transverse relative to a LD mounting surface, with the result being that a MPD coupled to the vertical MPD mounting surface gets positioned above an associated LD coupled to the LD mounting surface. The vertically-mounted MPD thus makes regions adjacent an LD that would otherwise be utilized to mount an MPD available for patterning of conductive RF traces to provide an RF driving signal to the LD. The conductive RF traces may therefore extend below the vertically-mounted MPD to a location that is proximate the LD to allow for relatively short wire bonds therebetween.

In a specific example embodiment, the vertical MPD mounting surface may be provided at least in part by a feedthrough device of the TOSA housing. The feedthrough device can be configured to be at least partially disposed in a hermetically-sealed cavity of the TOSA housing to provide electrical connectivity to optical components therein. The feedthrough device may also provide a conductive trace mounting surface that extends substantially transverse relative to the vertical MPD mounting surface for purposes of patterning the above-discussed conductive RF traces. Accordingly, an MPD may be securely mounted to the feedthrough device prior to insertion of the feedthrough device into a TOSA housing. Likewise, the conductive RF traces and other associated circuitry (e.g., filtering capacitors, conductive direct current (DC) traces, and so on) may be patterned/disposed when the feedthrough device is outside of the TOSA housing. Thus, insertion of the feedthrough device within the TOSA housing can result in the vertically-mounted MPD being passively optically aligned with an associated LD, and the conductive RF traces being brought within a predefined distance of the LD for electrical coupling purposes via, for instance, wire bonds.

The present disclosure therefore provides numerous advantageous over other TOSA approaches. For example, manufacturing of a TOSA may be conducted in a modular fashion whereby a feedthrough device and TOSA housing may be manufactured and configured separate from each other. For instance, components such as conductive traces and MPDs may be mounted/coupled to the feedthrough device in a parallel manufacturing process to allow for the TOSA housing and associated components to be completed apart from the feedthrough device, with the net result decreasing production time, reducing errors, and ultimately increasing yield. In addition, a TOSA housing with vertically-mounted MPDs consistent with the present disclosure advantageously reduces overall housing dimensions while allowing for LDs to be disposed in close proximity of conductive traces for electrical coupling purposes. RF signal quality may therefore be enhanced via relatively short wire bonds, for example, while simultaneously reducing cost, time-per-unit, and complexity to manufacture each TOSA.

As used herein, the terms hermetic-sealed and hermetically-sealed may be used interchangeably and refer to a housing that releases a maximum of about 5*10−8 cc/sec of filler gas. The filler gas may comprise an inert gas such as nitrogen, helium, argon, krypton, xenon, or various mixtures thereof, including a nitrogen-helium mix, a neon-helium mix, a krypton-helium mix, or a xenon-helium mix.

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. This disclosure is equally applicable to coarse wavelength division multiplexing (CWDM). In one specific example embodiment, the channel wavelengths are implemented in accordance with local area network (LAN) wavelength division multiplexing (WDM), which may also be referred to as LWDM.

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. On the other hand, the term “direct optical coupling” refers to an optical coupling via an optical path between two elements that does not include such intermediate components or devices, e.g., a mirror, waveguide, and so on, or bends/turns along the optical path between two elements.

The term substantially, as generally referred to herein, refers to a degree of precision within acceptable tolerance that accounts for and reflects minor real-world variation due to material composition, material defects, and/or limitations/peculiarities in manufacturing processes. Such variation may therefore be said to achieve largely, but not necessarily wholly, the stated characteristic. To provide one non-limiting numerical example to quantify “substantially,” minor variation may cause a deviation of up to and including ±5% from a particular stated quality/characteristic unless otherwise provided by the present disclosure.

Referring to the Figures,FIG. 1, an optical transceiver100, consistent with embodiments of the present disclosure, is shown and described. In this embodiment, the optical transceiver100includes a multi-channel TOSA arrangement and a multi-channel ROSA arrangement106coupled to a substrate102, which may also be referred to as an optical module substrate. The substrate102may comprise, for example, a printed circuit board (PCB) or PCB assembly (PCBA). The substrate102may be configured to be “pluggable” for insertion into an optional transceiver cage109.

In the embodiment shown, the optical transceiver100transmits and receives four (4) channels using four different channel wavelengths (λ1, λ2, λ3, λ4) via the multi-channel TOSA arrangement104and the multi-channel ROSA arrangement106, respectively, and may be capable of transmission rates of at least about 25 Gbps per channel. In one example, the channel wavelengths λ1, λ2, λ3, λ4may be 1270 nm, 1290 nm, 1310 nm, and 1330 nm, respectively. Other channel wavelengths are within the scope of this disclosure including those associated with local area network (LAN) wavelength division multiplexing (WDM). The optical transceiver100may also be capable of transmission distances of 2 km to at least about 10 km. The optical transceiver100may be used, for example, in Internet data center applications or fiber to the home (FTTH) applications. Although the following examples and embodiments show and describe a 4-channel optical transceiver, this disclosure is not limited in this regard. For example, the present disclosure is equally applicable to 2, 6, or 8-channel configurations.

In more detail, the multi-channel TOSA arrangement104includes a TOSA housing114with a plurality of sidewalls that define an optical component cavity220, which may be referred to as simply a cavity (SeeFIG. 4). The cavity220includes a plurality of laser arrangements110disposed therein, which will be discussed in more detail below, with each laser arrangement of the plurality of laser arrangements110being configured to transmit optical signals having different associated channel wavelengths. Each laser arrangement may include passive and/or active optical components such as a laser diode (LD), monitor photodiode (MPD), laser diode driver (LDD), and so on. Additional components comprising each laser arrangement include filters, focusing lenses, filtering capacitors, and so on.

To drive the plurality of laser arrangements110, the optical transceiver100includes a transmit connecting circuit112to provide electrical connections to the plurality of laser arrangements110within the housing114. The transmit connecting circuit112may be configured to receive driving signals (e.g., TX_D1to TX_D4) from, for example, circuitry within the optical transceiver cage109. As shown, the housing114may be hermetically sealed to prevent ingress of foreign material, e.g., dust and debris. Therefore, a plurality of transit (TX) traces117(or electrically conductive paths) are patterned on at least one surface of the substrate102and are electrically coupled with a feedthrough device116of the TOSA housing114to bring the transmit connecting circuit112into electrical communication with the plurality of laser arrangements110, and thus, electrically interconnect the transmit connecting circuit112with the multi-channel TOSA arrangement104. The feedthrough device116may comprise, for instance, ceramic, metal, or any other suitable material.

In operation, the multi-channel TOSA arrangement104may then receive driving signals (e.g., TX_D1to TX_D4), and in response thereto, generates and launches multiplexed channel wavelengths on to an output waveguide120such as a transmit optical fiber. The generated multiplexed channel wavelengths may be combined based on a multiplexing device124such as an arrayed waveguide grating (AWG) that is configured to receive emitted channel wavelengths126from the plurality of laser assemblies110and output a signal carrying the multiplexed channel wavelengths on to the output waveguide120by way of optical fiber receptacle122.

Continuing on, the multi-channel ROSA arrangement106includes a demultiplexing device124, e.g., an arrayed waveguide grating (AWG), a photodiode (PD) array128, and an amplification circuitry130, e.g., a transimpedance amplifier (TIA). An input port of the demultiplexing device124may be optically coupled with a receive waveguide134, e.g., an optical fiber, by way of an optical fiber receptacle136. An output port of the demultiplexing device124may be configured to output separated channel wavelengths on to the PD array128. The PD array128may then output proportional electrical signals to the TIA130, which then may be amplified and otherwise conditioned. The PD array128and the transimpedance amplifier136detect and convert optical signals received from the receive waveguide134, e.g., an optical fiber, into electrical data signals (RX_D1to RX_D4) that are output via the receive connecting circuit108. In operation, the PD array128may then output electrical signals carrying a representation of the received channel wavelengths to a receive connecting circuit132by way of conductive traces119(which may be referred to as conductive paths).

Referring now toFIGS. 2-3, an example optical transceiver module200is shown consistent with an embodiment of the present disclosure. The optical transceiver module200may be implemented as the optical transceiver100ofFIG. 1, the discussion of which is equally applicable toFIGS. 2-3and will not be repeated for purposes of brevity. As shown, the optical transceiver module200includes a substrate202that extends from a first end252to a second end254along a longitudinal axis250. The first end252may electrically couple to a transceiver cage to receive driving signals, e.g., TX_D1to TX_D4, and therefore, may be referred to as an electrical coupling end. On the other hand, the second end254includes a multi-channel TOSA arrangement204and a multi-channel ROSA arrangement206for sending and receiving channel wavelengths, respectively, and therefore may be referred to as an optical coupling end.

In more detail, the substrate includes at least a first mounting surface256for mounting of optical components, patterning of conductive traces (e.g., conductive traces117,119). Disposed adjacent the first end252, the substrate202includes a plurality of pads/terminals for electrically communicating with, for instance, associated circuitry in a transceiver cage. The substrate202includes a multi-channel TOSA arrangement204and multi-channel ROSA arrangement206disposed adjacent the second end. The multi-channel ROSA arrangement includes amplification circuitry230, a PD array228, and a demultiplexing device224disposed thereon. An input port235of the demultiplexing device224may be coupled to an optical coupling receptacle236by way of a receive intermediate fiber268. Accordingly, the demultiplexing device224can receive a multiplexed signal264from a receive waveguide, e.g., the receive waveguide134ofFIG. 1. An output port of the demultiplexing device224may be optically aligned with the PD array228and output separated channel wavelengths thereon. Electrical signals representative of the separated channel wavelengths may then be amplified/filtered by the amplification circuitry before being passed to the receive connecting circuit132.

As shown, the TOSA housing214is defined by a plurality of sidewalls. A first end258of the TOSA housing edge mounts to, and electrically couples with, the second end258of the substrate202. A second end259of the TOSA housing214couples to an optical coupling receptacle222by way of a transmit intermediate fiber269. The first end258of the TOSA housing214may also be referred to as an electrical coupling end, and the second end259may also be referred to as an optical coupling end. In an embodiment, the TOSA housing214may be securely attached to the substrate202via one or more electrical interconnect devices as discussed and described in greater detail in co-pending U.S. patent application. Ser. No. 16/116,087 filed on Aug. 29, 2018 and entitled “Transmitter Optical Subassembly with Hermetically-Sealed Light Engine and External Arrayed Waveguide Grating”, the teaching of which are hereby incorporated in their entirety.

In an embodiment, the TOSA housing214of the multi-channel TOSA arrangement204may be hermetically sealed, although in other embodiments the housing may not necessarily be hermetically sealed. Accordingly, the multi-channel TOSA arrangement204may also be referred to as a hermetically-sealed light engine that may be particularly well suited for long-distance transmission, e.g., up to and beyond 10 km. The TOSA housing214can include a feedthrough device262at least partially disposed in a cavity of the TOSA housing214to allow for electrical interconnection between the substrate202and the multi-channel TOSA arrangement204. The housing214may include a longitudinal axis that extends substantially parallel relative to the longitudinal axis250of the substrate202. The housing214may comprise, for example, metal, plastic, ceramic, or any other suitable material. The housing214may be formed from multiple pieces, or a single piece, of material.

The housing214may further define a laser cavity220(FIG. 4) which may be filled with an inert gas to form an inert atmosphere. In one embodiment, the inert atmosphere sealed within the hermetically-sealed container comprises nitrogen, and preferably, 1 atmosphere (ATM) of nitrogen. The inert atmosphere may also be formed from nitrogen, helium, argon, krypton, xenon, or various mixtures thereof, including a nitrogen-helium mix, a neon-helium mix, a krypton-helium mix, or a xenon-helium mix. The inert gas or gas mix included within the hermetically-sealed cavity220may be selected for a particular refractive index or other optical property. Gases may also be selected based on their ability to promote thermal insulation. For instance, Helium is known to promote heat transfer may be utilized alone or in addition to others of the aforementioned gases. In any event, the terms hermetic-sealed and hermetically-sealed may be used interchangeably and refers to a housing that releases a maximum of about 5*10−8 cc/sec of filler gas.

Turning toFIGS. 4-7, an example embodiment of the TOSA housing214of the multi-channel TOSA arrangement204is shown in isolation. As shown, the housing214extends from a first end452to a second end454along a longitudinal axis450. A plurality of sidewalls214-1to214-6define the TOSA housing214and a cavity220therebetween. Note, the embodiment shown inFIG. 4omits the sidewall214-6(FIG. 2) that forms a cover portion merely for purposes of clarity.

The feedthrough device262at least partially defines the first end452of the TOSA housing214and includes a plurality of electrical interconnects464, e.g., bus bars, external to the cavity220for mounting to and electrically coupling with the substrate102. The plurality of electrical interconnects464can provide power and radio frequency (RF) driving signals to the plurality of laser arrangements210. The feedthrough device262further includes at least one mounting surface such as a vertical monitor photodiode (MPD) mounting surface, which will be discussed in greater detail below.

Following the feedthrough device262within the cavity220, a plurality of laser arrangements210are disposed on and are supported by a mounting surface provided at least in part by the sidewall214-4. A multiplexing device224is also disposed on and supported by the mounting surface provided at least by the sidewall214-4. The multiplexing device224includes a plurality of input ports456, with each input port being optically aligned with an associated laser arrangement of the plurality of laser arrangements210. The multiplexing device224further includes an output port458which is shown more clearly inFIG. 6. The output port458of the multiplexing device224is optically aligned with an aperture462defined by the sidewall214-3of the TOSA housing214. The aperture462may then transition to a fiber coupling receptacle462, with the fiber coupling receptacle462being configured to receive the intermediate optical fiber269(FIG. 2).

Thus, in operation, the multiplexing device224receives channel wavelengths466emitted by the plurality of laser assemblies along direction D1at the plurality of inputs and then outputs a multiplexed signal468having each of the emitted channel wavelengths466for transmission via an external transmit optical fiber, for example.

FIG. 7shows an enlarged perspective view of the cavity220of the housing214in accordance with an embodiment. As shown, the feedthrough device262includes a step/shoulder configuration defined by a first mounting surfacing702that extends in parallel with the longitudinal axis450of the TOSA housing214, a second mounting surface704that extends parallel with the first mounting surface, and a third mounting surface706that adjoins the first and second mounting surfaces702,704and extends substantially transverse to each of the same. Thus, the first, second and third mounting surfaces702,704and706provide a multi-tiered or multi-step mounting structure for coupling to optical components. Each of the mounting surfaces of the feedthrough device262will now be discussed in turn.

The first mounting surface702includes a first plurality of conductive traces/paths708patterned thereon. The first plurality of conductive traces708may be configured to provide power from the substrate202and to pass data signals from a plurality of MPDs712that are mounted to and supported by the third mounting surface. To this end, the first mounting surface702may also be referred to as a MPD trace mounting surface/section. The second mounting surface704includes a second plurality of conductive traces/paths711disposed thereon. The second plurality of conductive traces/paths711may be configured to provide power and data signals from the substrate202to each of the plurality of lasers arrangements210. To this end, the second mounting surface704may be referred to as a LD trace mounting surface/section.

Continuing on, the third mounting surface706extends substantially transverse relative to the first and second mounting surfaces702,704and adjoins the same, as discussed above. The third mounting surface706may be configured to mount and support a plurality of MPDs shown collectively as712and individually as712-1to712-4. Each MPD of the plurality of MPDs712may be supported by a MPD submount714, with the MPD submount714providing electrical traces for electrically interconnecting MPDs to associated conductive traces of the MPD trace mounting section708. The MPD submount714may be a single piece, e.g., a single PCB or other suitable substrate, or may be multiple pieces. One advantage of a single piece MPD submount714is that attachment and alignment of MPDs to the feedthrough device262can be simplified as each MPD may be placed on to the MPD submount714at predefined positions prior to insertion of the feedthrough device262into the cavity202of the housing214. Accordingly, coupling the MPD submount714to the feedthrough device262optically aligns each of the MPDs disposed thereon without necessarily performing additional alignment steps.

As further shown, each MPD of the plurality of MPDs712includes a light receiving region, e.g., light receiving surface716-4of MPD712-4shown inFIG. 8B, on an upper/top surface of each chip that is optically aligned with a corresponding laser arrangement of the plurality of laser arrangements210. This vertical mounting of each MPD allows for a smaller overall footprint for the feedthrough device262, and by extension, shortens the overall length of the TOSA housing214. This vertical mounting configuration achieves housing size reduction by freeing the space behind/adjacent each laser arrangement to permit the LD traces of the second mounting surface704to extend below the plurality of MPDs712and be disposed in close proximity of the plurality of laser assemblies201. This removal of the MPDs from being behind/adjacent a corresponding laser arrangement also advantageously allows for relatively short electrical interconnection via wire bonding between the LD traces of the second mounting surface704and each laser arrangement, which reduces issues such as time of flight (TOF) and impedance mismatching that can ultimately degrade RF signal quality.

Continuing on, each of the plurality of laser arrangements210includes a laser diode supported by a laser submount213and optional thermoelectric cooling (TEC) arrangement. For instance, the laser arrangement210-4associated with channel4(CH4) includes a laser diode211-4mounted to and supported by the laser diode submount213. As shown in the cross-sectional view ofFIG. 8B, the laser diode submount213is mounted to and is supported by TEC devices720. In turn, TEC devices720are mounted to and supported by a surface provided by sidewall214-4of the TOSA housing214. The laser diode submount may also support thermistors such as thermistor724-4(FIG. 7). Following the plurality of laser assemblies210, each laser arrangement can include a focusing lens e.g., focusing lens726-4, mounted to and supported by the laser diode submount713. The laser submount213may comprise a single piece, such as shown, or may be formed from multiple pieces.

Following the plurality of laser arrangements210, the multiplexing device224is mounted to and is supported by a multiplexing submount720. The input ports456of the multiplexing device224are optically aligned with the plurality of laser arrangements210. To this end, a plurality of optical paths850extend longitudinally through the cavity220, with each optical path extending from a corresponding laser diode. A portion of optical power, e.g., 2% or less, gets emitted from a surface opposite the emission face of each LD (also known as a back-side emission surface) and is registered by each MPD, e.g., converted to a proportional electrical current, to form a feedback loop to ensure optical power. Thus, each of the plurality of optical paths850also intersects with the vertically mounted MPDs712, and more particularly, a light receiving region of each corresponding vertically mounted MPDs712, e.g., light receiving region716-4.

During operation, channel wavelengths emitted by each of the plurality of laser assemblies210is launched on to a corresponding path of the plurality of optical paths850, with each of the plurality of optical paths850extending substantially parallel relative to each other. As discussed above, a portion of the optical power gets emitted from a surface opposite of the emission surface of each laser diode, which may be referred to as a back-side emission surface, thus launching a portion of optical power towards the MPDs712. Each light receiving region of the MPDs, e.g., light receiving region716-4, then registers this portion of optical power for purposes of providing a feedback loop, e.g., by converting optical power to a proportional electrical current. The emitted channel wavelengths then get received via input ports456of the multiplexing device224. The multiplexing device224then combines the received channel wavelengths into a multiplexed optical signal263(seeFIG. 2). At an output458of the multiplexing device224the multiplexed signal263is output via the aperture on to the intermediate optical fiber269(SeeFIG. 2), and then ultimately to an external transmit optical fiber (not shown).

FIG. 9shows another example embodiment of a TOSA housing204′ in accordance with aspects of the present disclosure. As shown, the TOSA housing204′ includes a plurality of sidewalls to provide a cavity therebetween, which is substantially similar to that of the TOSA housing204. However, the TOSA housing204′ does not include a multiplexing device within the cavity and instead couples to a first end of a plurality of waveguides (not shown), e.g., optical fibers, via apertures480-1to480-4. A second end of the plurality of waveguides may be optically coupled to an external multiplexing device, such as an AWG. This allows the TOSA204′ to have a relatively small overall footprint, which can significantly reduce overall costs and complexity that characterizes hermetically-sealed housing. Put simply, the lesser the volume and number of passive/optical components within the cavity of the TOSA housing204′, the less the complexity, time and cost necessary to manufacture the TOSA housing204′. The feedthrough device262′ may be configured substantially similar to that of the feedthrough device262, the description of which is equally applicable to the embodiment ofFIG. 9but will not be repeated for brevity. For instance, the vertical MPD mounting surface490allows for MPDs to be mounted thereon to advantageously reduce the overall length of the TOSA housing204′ relative to other approaches that place MPDs behind or otherwise adjacent corresponding LDs.

In accordance with an aspect of the present disclosure a transmitter optical subassembly (TOSA) module is disclosed. The TOSA module comprising a laser diode (LD) mounting surface, at least a first LD disposed on the LD mounting surface, the first LD having a back-side emission surface for emitting a portion of optical power along a first optical path, a base portion providing a vertical MPD mounting surface, and a first MPD disposed on the vertical MPD mounting surface, the first MPD having a light receiving region optically aligned with the first LD via the first optical path based at least in part on the vertical MPD mounting surface extending substantially transverse relative to the LD mounting surface such that the first optical path intersects with the light receiving region of the first MPD.

In accordance with another aspect of the present disclosure a method for optically coupling monitor photodiodes (MPDs) to corresponding laser diodes (LDs) in a multi-channel optical transceiver (TOSA) housing is disclosed. The method comprising mounting at least one MPD to a vertical MPD mounting surface provided by a feedthrough device, patterning a plurality of conductive traces on to one or more surfaces of the feedthrough device, and inserting the feedthrough device into a cavity of the TOSA housing to bring the plurality of conductive traces into close proximity with the LDs in the TOSA, wherein inserting the feedthrough device into the cavity causes each of the at least one MPDs mounted to the vertical MPD mounting surface to optically couple with a back-side emission surface of each corresponding LD.

In accordance with yet another aspect of the present disclosure a multi-channel optical transceiver module is disclosed. The multi-channel optical transceiver including a printed circuit board assembly (PCBA), a transmitter optical subassembly (TOSA) arrangement coupled to the PCBA, the TOSA arrangement comprising a laser diode (LD) mounting surface, at least a first LD disposed on the LD mounting surface, the first LD having a back-side emission surface for emitting a portion of optical power along a first optical path, a base portion providing a vertical MPD mounting surface, a first MPD disposed on the vertical MPD mounting surface, the first MPD having a light receiving region optically aligned with the first LD via the first optical path based at least in part on the vertical MPD mounting surface extending substantially transverse relative to the LD mounting surface such that the first optical path intersects with the light receiving region of the first MPD.