阅读说明：本技术 用于一次模块壳体的一光输入/输出端口及设置于其中的一阵列波导光栅(awg)装置之间的间接光学耦合的技术 (Techniques for indirect optical coupling between optical input/output ports of sub-module housings and Arrayed Waveguide Grating (AWG) devices disposed therein ) 是由 何宜龙 彭罗汉 林恺声 马伦特斯·艾尔西 于 2018-06-05 设计创作，主要内容包括：本申请公开了一种用于弹性地耦接于光收发器壳体的光耦合插座/端口及位于其中的光学元件之间的技术。在一实施例中,光收发器壳体包括中间光纤,且中间光纤包括光学地耦接于光耦合端口的第一端及光学地耦接于多工器/解多工器装置,例如为阵列波导光栅(AWG)装置、PLC分光器等等,的第二端。中间光纤可以弯曲的半径被最佳化的方式绕设于收发器壳体以降低光纤弯曲损失。上述的技术同样地可应用于ROSA及光发射次组件模块且可用来达成用于多频道收发器装置的弹性耦合。(In embodiments, the optical transceiver housing includes an intermediate fiber that includes a end optically coupled to the optical coupling port and a second end optically coupled to a multiplexer/demultiplexer device, such as an Arrayed Waveguide Grating (AWG) device, a PLC splitter, etc. the intermediate fiber may be routed around the transceiver housing in a bend radius optimized manner to reduce fiber bend loss.)

1, an optical transceiver comprising:

a housing comprising a plurality of sidewalls extending along a long axis from an th end to a second end, wherein the sidewalls define a cavity having a long axis centerline of ;

an optical multiplexing device at least partially disposed in the cavity and having an input port with an th optical centerline;

an th optical coupling port at the th end of the housing, the optical coupling port having a second optical centerline;

an th optical fiber having a th end optically coupled to the optical coupling port and a second end optically coupled to the multiplexing device, and

wherein the th optical centerline of the input of the multiplexing device is laterally offset from the second optical centerline of the optical coupling port by a distance D.

2. The optical transceiver of claim 1, wherein the optical multiplexing device abuts against a distal wall of the housing opposite the optical coupling port.

3. The optical transceiver of claim 1, wherein the housing comprises a Transmitter Optical Subassembly (TOSA) module, and wherein the optical multiplexing device comprises a Planar Lightwave Circuit (PLC) splitter.

4. The optical transceiver of claim 3, wherein the optical multiplexing device comprises a reverse Planar Lightwave Circuit (PLC) splitter, and the reverse planar lightwave circuit splitter comprises a plurality of input ports for receiving a plurality of channel wavelengths from a plurality of associated laser components, and an output port for outputting a signal having the plurality of channel wavelengths, and wherein the th fiber is optically coupled to the output port.

5. The optical transceiver of claim 4, further comprising a plurality of laser assemblies disposed in the housing, each laser assembly configured to output a different channel wavelength, and wherein each laser assembly is optically coupled to a corresponding port of the input port via an optical fiber.

6. The optical transceiver of claim 1, wherein the optical multiplexing device comprises an Arrayed Waveguide Grating (AWG) device.

7. The optical transceiver of claim 1, wherein the th optical fiber includes or more bends to route the th optical fiber between the th optical coupling port and the optical multiplexing device.

8. The optical transceiver of claim 1, wherein the lateral offset D is at least 2 millimeters.

9. The optical transceiver of claim 1, wherein the transceiver is a small form-factor pluggable (SFP) transceiver module.

10, a multi-channel optical transceiver, comprising:

an emitter housing;

a plurality of Transmitter Optical Subassembly (TOSA) modules in the transmitter housing for transmitting a plurality of optical signals at different respective channel wavelengths;

a light output port disposed at an end of the transmitter housing for optically coupling to an external optical fiber; and

an optical multiplexer at a distal end of the transmitter housing and optically coupled to the tosas for multiplexing the optical signals into multiplexed optical signals including different channel wavelengths, wherein the optical multiplexer includes a plurality of multiplexing input ports optically coupled to the respective tosas and a multiplexing output port optically coupled to the optical output port, and the multiplexing input port has a plurality of output fibers for receiving respective optical signals,

wherein the multiplexed output port is optically coupled to the optical output port by an intermediate optical fiber.

11. The multi-channel optical transceiver of claim 11 wherein the optical output port has an th optical centerline and the multiplexed output port has a second optical centerline, and wherein the th optical centerline is not coaxially aligned with the second optical centerline.

12. The multi-channel optical transceiver of claim 11, the optical multiplexer comprising a Planar Lightwave Circuit (PLC) splitter.

13. The multi-channel optical transceiver of claim 11 wherein the intermediate optical fiber includes or more bends to wrap the th optical fiber between the th optical coupling port and the optical multiplexing device.

14. The multi-channel optical transceiver of claim 11 wherein the transceiver is a small form-factor pluggable (SFP) transceiver module.

Technical Field

The present invention relates to optical transmitters and transceivers, and more particularly to techniques for optically coupling an output/input port of a sub-module housing to an optical element located therein using a single optical fiber to allow for elastic positioning of the output/input port relative to the optical element.

Background

Optical transceivers may be used to send and receive optical signals for a variety of applications including, but not limited to, network data centers (internet data centers), cable TV broadband (cable TV broadband), and Fiber To The Home (FTTH). For example, transmission with an optical transceiver may provide higher speed over longer distances and bandwidths than transmission with copper cables. To provide higher speed in smaller optical transceiver modules at lower cost, challenges such as maintaining optical efficiency, thermal management, insertion loss, and yield are encountered.

Optical transceivers can include or more Transmitter Optical Subassembly (TOSA) and Receiver Optical Subassembly (ROSA) for transmitting and receiving optical signals, as channel density has grown to be an important aspect of optical transceivers, the ability to maintain nominal transceiver performance with reduced size has created several non-negligible challenges.

Drawings

The accompanying drawings, which are incorporated herein and constitute part of the specification, are included to provide a further understanding of the application, part of the application, illustrate embodiments of the application and together with the description serve to explain the application and not to limit the application.

Fig. 1 is a schematic diagram of a multi-channel optical transceiver including a multi-channel optical transmit subassembly and a multi-channel optical receive subassembly according to an embodiment of the present invention.

Fig. 2 is a perspective view of an optical transceiver having a multi-channel optical transmit subassembly and a multi-channel optical receive subassembly directly coupled to an optical coupling portion for coupling to an external transmitting fiber.

Fig. 3A is a top view of an embodiment in accordance with the present invention showing the transmitting portion of a multi-channel transceiver including an optical output port indirectly coupled to an optical fiber array of a multiplexing device through an intermediate optical fiber.

FIG. 3B is a top view of the optical multiplexer of FIG. 3A optically coupled to the input optical fiber and the output optical fiber according to the present invention.

Fig. 3C is a side view of the optical multiplexer of fig. 3A according to an embodiment of the present invention.

Fig. 4 is a top view of an embodiment of a receiver portion of a multi-channel transceiver according to the present invention, wherein the multi-channel transceiver includes an optical input port indirectly coupled to a demultiplexing device via an intermediate optical fiber.

Fig. 5 is a perspective view of the transmitting and receiving parts respectively shown in fig. 3A and 4, and the transmitting and receiving parts together form an optical transceiver according to an embodiment of the present invention.

Detailed Description

The optical transceiver device generally includes a housing having various optical components for transmitting and receiving channel wavelengths, such as an optical receive sub-assembly module and an optical transmit sub-assembly module, and an optical input/output port for optically coupling the optical components to external transmit and/or receive optical fibers, the specific location of the input/output port may be governed by a specific standard, for example, as shown in FIG. 2, the optical transceiver 200 implements a Small Form Factor Pluggable (SFFP) architecture including pairs of optical connection ports 210, and the optical connection ports 210 are LC connection ports disposed at the end of the housing 202. the specific location of the optical connection ports 210 limits the location of the multi-channel optical transmit sub-assembly 206 and the multi-channel optical receive sub-assembly 208, wherein the multi-channel optical transmit sub-assembly 206 and the multi-channel optical receive sub-assembly 208 are disposed at different portions of the housing 202. for example, assuming the spatial limitations of the optical connection of the housing 202, the optical transmit sub-assembly 206 and the optical receive sub-assembly 208 are disposed directly adjacent to the connection ports 208 and each include optical input/receive sub-assembly 213, and the optical components 213 are disposed directly adjacent to the optical centerline of the optical connection ports 206, 213, and the optical transceiver 202, 213, and the optical transceiver 210, the optical connection ports 213, the optical receive sub-optical connection ports, the optical connection ports, and the optical connection ports, and the optical transceiver's, and the optical connection ports, and optical transceiver's, such as.

, the optical transceiver housing includes an intermediate fiber having th end and a second end, wherein th end is optically coupled to the optical coupling port, and the second end is optically coupled to a multiplexer/demultiplexer such as an Arrayed Waveguide Grating (AWG) device, a PLC splitter (splitter), etc. the intermediate fiber may be routed in a transceiver housing by introducing or more bends, and the radius of the bend (also referred to as the bend radius) may be optimized to reduce fiber bend loss.

In a specific exemplary embodiment , the optical transceiver device includes a tosa housing portion and a tosa housing portion, each tosa and tosa housing portion being adapted to be coupled to collectively form the transceiver device, each tosa and tosa housing portion being associated with an optically coupled receptacle/port to optically couple each tosa and tosa module to an associated optical coupling port.

For example, optical components such as laser assemblies, multiplexing devices, demultiplexing devices, etc. may be disposed in the optical transceiver housing at various locations independent of the various optical coupling ports of the optical transceiver housing.

As used herein, "channel wavelength" refers to wavelengths associated with an optical channel and may include a particular band of wavelengths near a center wavelength in the example, channel wavelengths may be defined by International Telecommunications (ITU) standards, such as ITU-T Low Density wavelength division multiplexing (CWDM) or Dense Wavelength Division Multiplexing (DWDM) grid ("mount" as used herein refers to physically joining two structures, such as by soldering or using epoxy or other substances or means for joining.

Referring to fig. 1, fig. 1 presents and describes an optical transceiver 100 in accordance with an embodiment of the present invention. In the present embodiment, the optical transceiver 100 uses four different channel wavelengths (λ)₁、λ₂,λ₃,λ₄) Four channels are transmitted and received and may be used for low density wavelength division multiplexing (CWDM), but other numbers of channels are also within the scope of the invention, in the example, the channel wavelength λ₁、λ₂、λ₃、λ₄May be approximately 1270 nanometers (nm), 1290nm, 1310nm, and 1330nm, respectively. Optical transceiver 100 can have a transmission speed of at least about 25Gbps per channel. The optical transceiver 100 can also be used for short range transmissions such as tens of meters to distances of 2 kilometers or more. The optical transceiver 100 may be used, for example, for network data center applications (internet data centers) or Fiber To The Home (FTTH) applications.

In , the optical Transceiver 100 is implemented as a QSFP (Quad Small Form-Factor plug) Transceiver, for example, the optical Transceiver 100 may be implemented in a QSFP receiver compliant with the SFF Committee configuration SFF-8665for QSFP +28Gb/s 4X plug adaptor Solution (QSFP28) published at 10.5.2013.

The optical transceiver 100 includes a wavelength converter for converting an optical signal at a channel wavelength (e.g., λ)₁、λ₂、λ₃、λ₄) Multi-channel optical transmitter-receiver module for transmitting optical signals and method for transmitting optical signals at channel wavelengths (e.g., λ)₁、λ₂、λ₃、λ₄) An optical receive sub-assembly 130 that receives the optical signal. A multi-channel tosa 120 and a multi-channel rosa 130 are located in transceiver housing 102. In the housing 102, the transmitter connecting circuit 104 and the receiver connecting circuit 108 are electrically connected to the multi-channel transmitter subassembly 120 and the multi-channel receiver subassembly 130, respectively. The transmit connection 104 is electrically connected to the electronics (e.g., lasers, monitoring photodiodes, etc.) in the multi-channel tosa 120, and the receive connection 108 is electrically connected to the electronics (e.g., photodiodes, TIA, etc.) in the multi-channel tosa 130. The transmit connection circuitry 104 and the receive connection circuitry 108 include at least conductive paths (conductive paths) to provide electrical connections, and may also include additional circuitry. The transmitting connection circuit 104 and the receiving connection circuit 108 can communicate with an external system through a data bus, and the data bus is, for example, a 38-pin connector conforming to the physical connector QSFP standard and data communication protocols (data communication protocols).

In the present embodiment, the tosa 120 includes a plurality of tosa modules 124-1 to 124-4 optically coupled to the multiplexer 122, wherein the multiplexer 122 has the mux-inputs 126-1 to 126-4 and the mux-output 128 on the same side, an example of an wdm having the mux-inputs and the mux-outputs on the same side is described in more detail in U.S. patent application publication No. 2018 and 0017745 (application No. 15/210,193), which is incorporated herein by reference.

The OSA modules 124-1 to 124-4 may be coupled to the multiplexer input ports 122-1 to 122-4 of the optical multiplexer 122 using optical fibers, the optical multiplexer 122 may be an arrayed waveguide grating or an inverse PLC splitter, an example of for an inverse PLC splitter used as an optical multiplexer is described in more detail in U.S. patent application publication No. 2017-0359126 (application No. 15/176,404), which is hereby incorporated by reference, another advantage of a PLC splitter is wavelength independent and thus less susceptible to wavelength shifts (e.g., due to temperature changes).

Although the optical multiplexer 122 is shown adjacent to the tosas 124-1-124-4 in this illustration, the optical multiplexer 122 may be located remotely from the tosas 124-1-124-4 in the transceiver housing 102, as described in more detail below. The tosas 124-1-124-4 operate at different respective channel wavelengths (e.g., λ)₁、λ₂、λ₃、λ₄) Optical signals are generated and optical multiplexer 122 combines or multiplexes those optical signals to provide a multiplexed optical signal to a multiplexed output port 128 coupled to output fiber 115. The output optical fiber 115 is coupled to an output optical connector 116 such as an LC connector.

Each of the tosa modules 124-1 through 124-4 may have an on-axis pattern such that the end of the tosa module is electrically connected to a conductive path on the tx connection circuit 104 and the end is optically coupled each tosa module 124-1 through 124-4 may be indirectly aligned with the output optical connector 116, such as off-axis (off-axis), and optically coupled thereto by an intermediate optical fiber as described in further below, which allows the tosa modules 124-1 through 124-4 to be disposed in various positions in the housing 102 without being directly aligned with the output optical connector 116.

Each of the tosa modules 124-1 through 124-4 may then include a laser for generating laser light at the designated channel wavelength and an optical structure for optically coupling the laser light into the respective multiplexed input port of the multiplexer 122. the lasers in the tosa modules 124-1 through 124-4 may thus convert the electrical data signals (TX _ D1 through TX _ D4) received through the TX connection circuit 104 into modulated optical signals that are coupled into the multiplexer 122. the lasers may include, for example, Distributed Feedback (DFB) lasers with diffraction gratings. each of the tosa modules 124-1 through 124-4 may also include a monitor photodiode (laser diode) for monitoring light emitted by the laser. each of the tosa modules 124-1 through 124-4 may further include a temperature control device or a plurality of temperature control devices, such as a resistive heater and/or a thermoelectric cooler (TEC), for controlling the temperature of the laser light, for example, to control the wavelength of the laser light.

In the present embodiment, the multi-channel light receiving sub-assembly 130 includes an optical demultiplexer 132 coupled to an optical sensor array 134, wherein the optical sensor array 134 includes, for example, a photodiode. The optical demultiplexer 132 demultiplexes or separates the optical signals received and multiplexed on the input fiber 117 to provide the received optical signals at different channel wavelengths, which can be detected by each of the optical sensors in the optical sensor array 134. The input optical fiber 117 is coupled to an input optical connector 118, such as an LC connector. The multi-channel rosa 130 also includes a multi-channel transimpedance amplifier 136 electrically connected to the photosensor array 134. The optical sensor array 134 and the transimpedance amplifier 136 detect the optical signal received from the optical demultiplexer 132 and convert the optical signal into an electrical data signal (RX _ D1-RX _ D4) output via the receive connection circuit 108.

Although an example of multi-channel light receiving subassembly 130 is described, optical transceiver 100 may include other types or embodiments of light receiving subassemblies in other embodiments, a multi-channel optical transmitter may include transmit circuitry 104, multi-channel light transmitting subassembly 120, and output optical connector 116 (i.e., a transmit section) without receive circuitry 108, multi-channel light receiving subassembly 130, and input optical connector 118 (i.e., a receive section). the multi-channel light receiving subassembly 130 may be indirectly aligned with, e.g., off-axis, and optically coupled to input optical connector 118 via an intermediate optical fiber, as described in further below, which may allow multi-channel light receiving subassembly 130 to be positioned in various locations in housing 102 without being directly aligned to input optical connector 118.

Referring to fig. 3A-3C, the transmitter of the embodiment of the multi-channel optical transceiver 300 is described in detail and presented, the optical transceiver 300 includes a transceiver housing 302 that houses optical sub-assembly components and optical sub-assembly components (not shown), in this embodiment, the optical output port 316, such as an LC connector, extends substantially parallel to the long axis 350 of the housing 302, the optical sub-assembly modules 324-1 to 324-4 and the optical multiplexer 322 may also extend substantially parallel to the long axis 350, but the invention is not limited thereto.

In addition, an optical multiplexer 322 having multiplexed input and output ports on side is located at the distal end 302a of the optical transceiver housing 302. in the illustrated embodiment, the optical multiplexer 322 abuts (abut) against the distal wall 301 of the transceiver housing 302. in other embodiments, the optical multiplexer 322 may be adjacent to the distal wall 301 but need not abut against the distal wall 301. the optical multiplexer 322 may be secured between a plurality of structures 303 extending from the housing 302.

Referring next to FIG. 3A, the optical output port 316, or optical output receptacle 316, includes an optical centerline (shown schematically as extending along the major axis 351) that is offset laterally from the optical center of each of the tosas 324-1-324-4 (and more specifically the tosa optical coupling modules 340-1-340-4) by a distance D. for example, the optical center of the tosa module 324-1 includes an offset 355 relative to the optical centerline of the optical output port 316. in some cases, each offset is at least 2 millimeters (millimeter). further, the optical centerline of the optical output port 316 may be offset laterally relative to the optical centerline 355 of the mux output port 353 of the optical multiplexer 322. similarly, each optical centerline of the tosas 324-1-324-4 may be offset relative to the optical centerline of each corresponding mux input port, shown schematically as 354.

With continued reference to FIG. 3A, the optical fiber 327 includes an th end and a second end, wherein the th end is optically coupled to the optical output port 316 and the second end is optically coupled to the multiplexed output port 353 of the optical multiplexer 322 in the housing 302. similarly, the optical fibers 325-1 through 325-4 include a th end and a second end, the th end is optically coupled to each of the optical sub-assembly modules 324-1 through 324-4 and the second end is optically coupled to each of the multiplexed input ports, represented by 355. the optical output port 316 may thus be accurately described as being indirectly coupled to the multiplexer device 322. this advantageously allows the optical output port 316 to be elastically coupled to the optical fiber array of the multiplexer device 322, such as the optical fibers 325-1 through 325-3, without regard to the exact location of the optical output port 316 relative to the optical multiplexer device 322 and/or the optical sub-assembly modules 324-1 through 324-4.

With continued reference to FIG. 3A, the optical multiplexer 322 includes a plurality of multiplexed input ports 354 and multiplexed output ports 354, wherein the plurality of multiplexed input ports 354 are respectively represented at 326-1 through 326-4 in FIG. 3B, and the multiplexed output ports 354 are all located at the same side 321 (referred to herein as the optical coupling side). As shown in FIG. 3A, the distal side 323 of the optical multiplexer 322 (e.g., relative to the optical coupling side 321) is adjacent or abutting the distal wall 301 of the transceiver housing 302, and the optical coupling side 321 is directed toward (directed) other optical sub-assembly components in the transceiver housing 302. this arrangement facilitates the use of the optical fibers 325-1 through 325-4 for coupling without bending the optical fibers, thereby advantageously reducing fiber bending losses.

The optical multiplexer 322 may be an arrayed waveguide grating having an input port and an output port, and the input port and the output port are located on the same side of or on a crystal plane (face) of the arrayed waveguide grating chip, the optical multiplexer 322 may also be a Planar Lightwave Circuit (PLC) splitter having an optical splitter input port (used as a multiplexing output port) and an optical splitter output port (used as a multiplexing input port), and the optical splitter input port and the optical splitter output port are located on the same side of or on a crystal plane of the PLC splitter chip.

As shown in detail in fig. 3B and 3C, with additional reference to fig. 3A, fiber array positioner 356 is configured to maintain input fibers 325-1 to 325-4 and output fibers 327 in alignment, and is configured to optically couple input fibers 325-1 to 325-4 and fibers 327 to respective multiplexed input ports 326-1 to 326-4 and multiplexed output ports 353 located at optical coupling side 321 of optical multiplexer 322. in this embodiment, fiber array positioner 356 includes a base portion 352 and a top portion 357, wherein base portion 352 includes a V-groove 359 to receive respective fibers, and top portion 357 secures fibers in V-groove 354. optical coupling side 321 may have an angle of degrees α with a line segment orthogonal to the top and/or bottom multiplexers of optical multiplexer 322. fiber array positioner 356 has a corresponding angled coupling surface to enable the angled fiber ends to couple to the angled multiplexed input ports, which reduces back side reflection (back reflection) and increases coupling efficiency. in the example, optical 322 with fiber array positioner 356 may have a length that is shorter than 15 mm, more specifically about 12.2 mm, and more specifically may be about 4 mm and less than 222 mm.

The multiplexed input fibers 325-1 through 325-4 are optically coupled to the plurality of tosa modules 324-1 through 324-4 using the tosa optical coupling assemblies 340-1 through 340-4, the tosa modules 324-1 through 324-4 are located at another portion of the housing 302 such that the optical multiplexer 322 is spaced apart from the tosa modules 324-1 through 324-4 to reduce thermal effects (thermal effects) from heat generated by the tosa modules 324-1 through 324-4. the tosa optical coupling assemblies 340-1 through 340-4 may include or a plurality of optical coupling sleeves 342-1 through 342-4 (fig. 3B), the optical coupling sleeves-1 through 342-4 are inserted into coupling receptacles extending from the tosa modules 324-1 through 324-4 to provide optical alignment and coupling.

Referring to fig. 4, a receiver portion of a embodiment of a multi-channel optical transceiver 400 is shown and described in detail, in this embodiment, an optical output port 418, such as an LC connector, extends substantially parallel to a long axis 450 of a housing 402. a de-multiplexing device 432 is disposed in the housing 402 adjacent to a distal side 423 of the housing 402. as shown in the figure, an optical fiber 427 is disposed in the housing 402 and includes a th end and a second end, wherein the th end is coupled to the optical input port 418 and the second end is optically coupled to an optical coupling receptacle/component 442 of the de-multiplexing device 432. in the de-multiplexing device 432 to the distal end of the optical coupling receptacle 442, the multiplexing device may be coupled to associated circuitry, such as an optical diode array, a transimpedance amplifier (TIA), a receiver circuit, etc.

As shown in the drawing, the optical fiber 427 is wound with a relatively large bending radius to advantageously reduce bending loss. This increase in bend radius may be achieved, at least in part, by the location of the multiplexing device 432 in the housing 402. Additional examples of multiplexing devices 432 and associated final bend radii for optical fibers are described in more detail in U.S. patent application No. _____________ (application No. 15/242,005), which is hereby incorporated by reference.

With continued reference to FIG. 4, the optical coupling receptacle 442 is shown indirectly and optically coupled to the demultiplexing device 432 via the optical fiber 427. in particular, the optical centerline 451 of the optical coupling receptacle 442 is horizontally offset by a distance D, which may be measured between 2 mm and 10 mm, although other offsets are within the scope of the present invention.

Referring again to FIG. 5, an optical transceiver module 500 having a segmented housing is presented in accordance with an embodiment, as shown in the drawing, the housing 302 of the multi-channel transceiver 300 is coupled to the housing 402 of the multi-channel ROSA 400 and collectively forms the optical transceiver 500. an example of the segmented optical transceiver housing is described in greater detail in U.S. patent application publication No. _____________ (application No. 15/242,017), which is hereby incorporated by reference.

A optical transceiver is disclosed according to an embodiment of the invention the optical transceiver includes a housing, an optical multiplexing device, a 0 optical coupling port and a 1 th optical fiber, the housing includes a plurality of sidewalls extending along a long axis from a th end to a second end, wherein the sidewalls define a cavity having a th long axis centerline, the optical multiplexing device is at least partially disposed in the cavity and has an input port, and the input port has a th optical centerline, a th optical coupling port is located at this th end of the housing, the optical coupling port has a second optical centerline, a th optical fiber has a th end optically coupled to the optical coupling port and a second end optically coupled to the multiplexing device, the th optical centerline of the input of the multiplexing device is horizontally offset from the second optical centerline of the optical coupling port by a distance D.

Another embodiment of the present invention discloses a multi-channel optical transceiver, comprising a transmitter housing, a plurality of Transmitter Optical Subassembly (TOSA) modules positioned in the transmitter housing for transmitting a plurality of optical signals at different respective channel wavelengths, an optical output port disposed at a end of the transmitter housing for optically coupling to an external optical fiber, and an optical multiplexer positioned at a distal end of the transmitter housing and optically coupled to the TOSA modules for multiplexing the plurality of optical signals into a multiplexed optical signal including the different channel wavelengths.

While the principles of the invention have been described herein, it will be understood by those skilled in the art that these descriptions are made only by way of example and not as a limitation on the scope of the invention.