Patent Publication Number: US-2023161122-A1

Title: Silicon photonics optical transceiver device

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority of Taiwanese Invention Patent Application No. 110143331, filed on Nov. 22, 2021, the contents of which are incorporated herein by reference in its entirety. 
     FIELD 
     The disclosure relates to an optical transceiver device, and more particularly to a silicon photonics optical transceiver device. 
     BACKGROUND 
     Referring to  FIG.  1   , U.S. Patent Application Publication No. 2017/0059796 A1 discloses a conventional optical transceiver device  200  that is operable to convert electric signals into optical signals, to convert optical signals into electric signals, and to transmit optical signals and electrical signals. The conventional optical transceiver device  200  includes a processor  202  and multiple hermetic optical transmitter components  203  that are all mounted to a first surface of a substrate  201 , and an optical receiver component  204  that is mounted to a second surface of the substrate  201 . The optical transmitter components  203  and the optical receiver component  204  are electrically connected to the processor  202 . The optical transmitter components  203  have hermeticity satisfying an airtightness requirement for industrial transmitter optical sub-assemblies (TOSAs), and are closely arranged side by side on the substrate  201 . 
     During operation of the light emitter (e.g., a photoelectric chip; not shown) of each optical transmitter component  203 , an input current cannot be fully converted into photoelectrons, and part of the input current will become energy loss in the form of heat. However, installation of cooling components for heat dissipation is hardly possible, especially for a miniaturized package, since the optical transmitter components  203  in the conventional optical transceiver device  200  are closely arranged side by side. Further, more heat may be generated when the processor  202  utilizes relatively complex 4-level pulse amplitude modulation (PAM4) to perform signal modulation at higher optical communication rates, such as 400 Gbps. If a large amount of heat continues to accumulate in the conventional optical transceiver device  200  and cannot be removed in time, there may be many adverse impacts on the performance of the conventional optical transceiver device  200 . For example, the service life of components may be reduced, the performance may be deteriorated, materials may be aged or deformed. In the worst case, the components may be damaged or malfunction. 
     SUMMARY 
     Therefore, an object of the disclosure is to provide a silicon photonics optical transceiver that is adapted for high-speed optical fiber communication and that has good heat dissipation capability. 
     According to the disclosure, the silicon photonics optical transceiver device includes a silicon photonics optical module and a heat conducting housing. The silicon photonics optical module includes a substrate, a plurality of transmitter optical sub-assemblies (TOSAs), a digital signal processor and a silicon optical sub-assembly (SOSA). The substrate has an installation surface, is formed with a plurality of conductive traces, extending in an extending direction, and has a first end and a second end that are opposite to each other in the extending direction. The TOSAs are disposed on the first end of the substrate and extend away from the substrate in the extending direction. Each of the TOSAs is electrically connected to a corresponding part of the conductive traces, and has an optical port. The digital signal processor is mounted to the installation surface of the substrate and is spaced apart from the TOSAs. The SOSA is mounted to the installation surface of the substrate, and includes a photonic integrated circuit, a laser diode driver, a transimpedance amplifier, a polarization-maintaining optical fiber (PMF) component and a transmission optical fiber component. The photonic integrated circuit is fixedly mounted to the installation surface of the substrate, includes at least a beam splitter, a modulator and a photodiode, and has a first optical port segment and a second optical port segment, each having a plurality of optical ports. The laser diode driver and the transimpedance amplifier are electrically connected to and integrated with the photonic integrated circuit. Each of the laser diode driver and the transimpedance amplifier is electrically connected to the digital signal processor through a corresponding part of the conductive traces. The PMF component includes a first optical coupler seat which is coupled to the first optical port segment of the photonic integrated circuit, a plurality of connectors which are respectively coupled to the optical ports of the TOSAs, and a plurality of PMFs each of which is coupled between the first optical coupler seat and a respective one of the connectors. Each of the PMFs has an end portion optically coupled to a corresponding one of the optical ports of the first optical port segment of the photonic integrated circuit through the first optical coupler seat. The transmission optical fiber component includes a second optical coupler seat which is coupled to the second optical port segment of the photonic integrated circuit, an optical fiber connector, and a plurality of optical-fiber cables which are coupled between the second optical coupler seat and the optical fiber connector. Each of the optical-fiber cables includes a plurality of optical fibers, each having an end portion optically coupled to a corresponding one of the optical ports of the second optical port segment of the photonic integrated circuit through the second optical coupler seat. The heat conducting housing is formed with an inner accommodating space, a first opening, a second opening opposite to the first opening, and an inner surface defining the inner accommodating space. The inner accommodating space is for fittingly and firmly accommodating the silicon photonics optical module therein. The first opening is in spatial communication with the inner accommodating space for exposing the optical fiber connector. The inner surface has a first heat dissipation portion and a second heat dissipation portion. The first heat dissipation portion wraps around and is in contact with the TOSAs to realize thermal conduction, and the second heat dissipation portion is in contact with a surface of the digital signal processor, so as to transfer heat generated during operation of the TOSAs and the digital signal processor outside of the heat conducting housing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other features and advantages of the disclosure will become apparent in the following detailed description of the embodiment(s) with reference to the accompanying drawings, of which: 
         FIG.  1    is an exploded perspective view illustrating a conventional optical transceiver device; 
         FIG.  2    is a perspective view illustrating an embodiment of a silicon photonics optical transceiver device according to the disclosure; 
         FIG.  3    is an exploded perspective view illustrating the embodiment; 
         FIG.  4    is another exploded perspective view illustrating the embodiment; 
         FIG.  5    is a perspective view illustrating a silicon optical sub-assembly of the embodiment; 
         FIG.  6    is a perspective view illustrating a transmitter optical sub-assembly of the embodiment; and 
         FIG.  7    is a block diagram illustrating a photonic integrated circuit of the embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Before the disclosure is described in greater detail, it should be noted that where considered appropriate, reference numerals or terminal portions of reference numerals have been repeated among the figures to indicate corresponding or analogous elements, which may optionally have similar characteristics. 
     Referring to  FIGS.  2  to  4   , an embodiment of a silicon photonics optical transceiver device  100  is adapted for receiving optical signals provided by an external optical transmitter (not shown), and/or for transmitting optical signals to an external optical receiver (not shown). The silicon photonics optical transceiver device  100  includes a silicon photonics optical module  3  and a heat conducting housing  1 . 
     In this embodiment, the silicon photonics optical module  3  includes a substrate  31 , multiple (not limited to two) transmitter optical sub-assemblies (TOSAs)  32 , a silicon optical sub-assembly (SOSA)  33 , a digital signal processor (DSP)  34 , a microcontroller (MC)  35  and a driver controller  36 , but this disclosure is not limited in this respect. 
     The substrate  31  is, for example, a printed circuit board (PCB), has a first end and a second end that are opposite to each other in a direction (referred to as extending direction hereinafter) that the substrate  31  extends in, and an installation surface  311 , and is formed with a plurality of conductive traces. In some embodiments, the second end of the substrate  31  is a connecting end formed with gold fingers. 
     Referring to  FIGS.  3  and  6   , the TOSAs  32  are disposed at the first end of the substrate  31  and extend away from the substrate  31  in the extending direction. Each of the TOSAs  32  may have, for example, a high-power laser diode built therein and an optical port  321 , and is configured to generate a to-be-transmitted optical signal based on a driving signal. In this embodiment, each of the TOSAs  32  includes a flexible printed circuit (FPC)  322  that is soldered onto the installation surface  311  of the substrate  31  for electric connection to a corresponding part of the conductive traces, so as to receive, through the corresponding part of the conductive traces and the FPC  322 , the driving signal from the substrate  31 . 
     The DSP  34  is disposed on the installation surface  311  of the substrate  31  and is spaced far apart from the TOSAs  32  to minimize potential adverse effects arising from heat generated by the TOSAs  32 . In some embodiments, the DSP  34  is spaced apart from the TOSAs  32  by a distance that is greater than, for example but not limited to, 20 mm. 
     Referring to  FIGS.  3  and  5   , the SOSA  33  is mounted to the installation surface  311  of the substrate  31 , and includes, for example, a photonic integrated circuit (PIC)  331 , a laser diode driver (LDD)  332 , a transimpedance amplifier (TIA)  333 , a polarization-maintaining optical fiber (PMF) component  334 , and a transmission optical fiber component  335 . 
     Further referring to  FIG.  7   , the PIC  331  is produced using a silicon photonics manufacturing process, includes, for example, a beam splitter, a modulator and a photodiode, and has a first optical port segment  3311  and a second optical port segment  3312 , each having a plurality of optical ports. In this embodiment, the PIC  331  is electrically connected to a corresponding part of the conductive traces of the substrate  31  using, for example, wire bonding, and is electrically connected to the DSP  334  and the FPCs  322  of the TOSAs  32  through the corresponding part of the conductive traces. In this embodiment, a strengthening substrate may be added to a bottom of the PIC  331 , to be fixed onto the installation surface  311  of the substrate  31  through thermal glue, so as to enhance structural strength of the assembled SOSA  33 . 
     In this embodiment, the LDD  332  and the TIA  333  are integrated/combined with the PIC  331 , and are electrically connected to the PIC  331 . As an example, the LDD  332  and the TIA  333  may be stacked on and electrically connected to the PIC  331  by flip chip, so the LDD  332  and the TIA  333  are electrically connected to the DSP  34  through the wire bonded between the PIC  331  and the part of the conductive trances that corresponds to the PIC  331 , but this disclosure is not limited in this respect. In other embodiments, it may be possible that the LDD  332  and the TIA  333  are not stacked on the PIC  311 , and are instead mounted onto the installation surface  311  through wire bonding. In such a configuration, the LDD  332  would be electrically connected to the DSP  34  and the PIC  331  through corresponding conductive traces, and the TIA  333  may be electrically connected to the photodiode of the PIC  331  through corresponding conductive traces. 
     The driver controller  36  is mounted to the installation surface  311  of the substrate  31 , is electrically connected to the PIC  331  through a corresponding part of the conductive traces, and is operable to generate a direct current (DC) driver signal that is related to the TOSAs  32 , wherein the DC driver signal may be a voltage signal or a current signal. The LDD  332  is operable to generate a radio frequency (RF) signal that is related to the TOSAs  32  and to modulation performed by the modulator of the PIC  331 . With respect to each of the TOSAs  32 , the PIC  331  generates and outputs the driving signal to the TOSA  32  based on the DC driver signal and the RF signal that are received from the driver controller  36  and the LDD  332 , respectively. In some embodiments, the driver controller  36  and the LDD  332  may be integrated into a single chip. 
     Referring to  FIGS.  3 ,  5  and  6   , the PMF component  334  includes a first optical coupler seat  3341 , multiple connectors  3342 , and multiple PMFs  3343 . The first optical coupler seat  3341  is coupled to the first optical port segment  3311  of the PIC  331 . The connectors  3342  are respectively coupled to the optical ports  321  of the TOSAs  32 . Each of the PMFs  3343  is coupled between the first optical coupler seat  3341  and a respective one of the connectors  3342 , and has an end portion optically coupled to a corresponding one of the optical ports of the first optical port segment  3311  of the PIC  331  through the first optical coupler seat  3341 . In this embodiment, the first optical coupler seat  3341  is glued to the first optical port segment  3311  of the PIC  331  in order to ensure reliability in terms of transmission of optical signals. 
     The transmission optical fiber component  335  includes a second optical coupler seat  3351 , an optical fiber connector  3352 , and multiple optical-fiber cables  3353 . The second optical coupler seat  3351  is coupled to the second optical port segment  3312  of the PIC  331 . The optical fiber connector  3352  is configured for connection with an external fiber connector (not shown). The optical-fiber cables  3353  are coupled between the second optical coupler seat  3351  and the optical fiber connector  3352 . Each of the optical-fiber cables  3353  includes a plurality of optical fibers, each having an end portion optically coupled to a corresponding one of the optical ports of the second optical port segment  3312  of the PIC  331  through the second optical coupler seat  3351 . In this embodiment, the second optical coupler seat  3351  is glued to the second optical port segment  3312  of the PIC  331 . 
     The microcontroller  35  is mounted to the installation surface  311  of the substrate  31 , and is configured to provide firmware control related to the silicon photonics optical module  3 . 
     Referring to  FIGS.  2  through  4   , the heat conducting housing  1  (e.g., made of, for example but not limited to, zinc alloy, copper, tungsten-copper alloy, aluminum, etc.) is formed with an inner accommodating space for fittingly and firmly accommodating the silicon photonics optical module  3  therein, and has a first opening  13  and a second opening  14  that are opposite to each other in the extending direction. The first opening  13  is in spatial communication with the inner accommodating space for exposing the optical fiber connector  3352 , and the second opening  14  is in spatial communication with the inner accommodating space for exposing the second end (i.e., the connecting end) of the substrate  31 . The heat conducting housing  1  has an inner surface that defines the inner accommodating space, and that has a first heat dissipation portion and a second heat dissipation portion, wherein the first heat dissipation portion is configured to be in contact with the TOSAs  32  to realize thermal conduction, and the second heat dissipation portion is configured to be in contact with the DSP  34  to realize thermal conduction. In this embodiment, the heat conducting housing  1  includes a seat body  11  that is configured for holding the silicon photonics optical module  3 , and a cover body  12  that covers the installation surface  311  of the substrate  31 . The cover body  12  has an inner surface (which is a part of the inner surface of the heat conducting housing  1 ) formed with a heat dissipation bump  121  and a first heat sink  122 . The heat dissipation bump  121  serves as the second heat dissipation portion, corresponds in position to the DSP  34 , and fittingly contacts a surface of the DSP  34 . The first heat sink  122  corresponds in position to the TOSAs  32 , and covers part of the TOSAs  32 . In this embodiment, the first heat sink  122  has a plurality of first concave (arc-shaped and curved inward) surfaces  1221 , each of which fittingly contacts a respective one of the TOSAs  32 . The seat body  11  has an inner surface (which is the remaining part of the inner surface of the heat conducting housing  1 ) formed with a second heat sink  111  that corresponds in position to the TOSAs  32  and that covers part of the TOSAs  32 . In this embodiment, the second heat sink  111  has a plurality of second concave surfaces  1111 , each of which fittingly contacts a respective one of the TOSAs  32 . As a result, each of the second concave surfaces  1111  of the second heat sink  111  cooperates with a corresponding one of the first concave surfaces  1221  of the first heat sink  122  to wrap around the respective one of the TOSAs  32 , and the first heat sink  122  and the second heat sink  111  cooperatively constitute the first heat dissipation portion that wraps around and is in contact with the TOSAs  32  to realize thermal conduction. Therefore, the heat generated during operation of the TOSAs  32  and the DSP  34  may be transferred to the cover body  12  and the seat body  11  through the first and second heat dissipation portions, and is then released to the outside of the heat conducting housing  1 . In this embodiment, an outer surface of the cover body  12  is formed with a plurality of cooling fins  123  (see  FIG.  3   ) that correspond in position to the first heat sink  122 , so as to release the heat to the environment more rapidly. 
     During operation, when the silicon photonics optical transceiver device  100  receives an external optical signal through the transmission optical fiber component  335 , the photodiode of the PIC  331  would convert the optical signal into a current signal, and the TIA  333  would convert the current signal into a voltage signal, and transmit the voltage signal to the DSP  34  for subsequent processing. When the silicon photonics optical transceiver device  100  is used to output an optical signal, the DSP  34  outputs a control signal that is related to the optical signal to the LDD  332 , and the LDD  332  generates an RF signal based on the control signal. Then, the PIC  331  provides a driving signal to each of the TOSAs  32  based on a DC driver signal received from the driver controller  36  and the RF signal received from the LDD  332 , and the TOSAs  32  emit a two-way optical signal to the PIC  331  through the PMF component  334 . After modulation and split-beam processing, the two-way optical signal is converted into, for example, a four-way optical signal that is subsequently transmitted outside of the silicon photonics optical transceiver device  100  through the transmission optical fiber component  335 . 
     In summary, the embodiment of the silicon photonics optical transceiver device  100  according to this disclosure may have the following advantages: 
     1. The PIC  331  integrates the beam splitter, the modulator and the photodiode therein, and has the LDD  332  and the TIA  333  staked thereon, so an area of the substrate  31 , which is a PCB in the embodiment, can be reduced, thereby favoring reduction of overall dimensions of the silicon photonics optical transceiver device  100 . Furthermore, the use of the beam splitter may reduce a number of the TOSAs  32  to be used in the silicon photonics optical transceiver device  100 . 
     2. The first heat dissipation portion can effectively transfer the heat generated by the TOSAs  32  outside of the heat conducting housing  1 , so high-power laser diodes that do not need impedance matching can be used in the TOSAs  32 , thereby avoiding electric reflection noises from poor impedance matching. 
     3. The first optical coupler seat  3341  and the second optical coupler seat  3351  are respectively coupled to the first and second optical port segments  3311 ,  3312  using glue, thereby promoting reliability in terms of transmission of optical signals. 
     4. The first and second heat dissipation portions are respectively in contact with the TOSAs  32  and the DSP  34  to realize thermal conduction, so the heat generated by the TOSAs and the DSP  34  can be effectively and rapidly transferred to the outside of the heat conducting housing  1  through the first and second heat dissipation portions and the cooling fins  123 . 
     In the description above, for the purposes of explanation, numerous specific details have been set forth in order to provide a thorough understanding of the embodiment(s). It will be apparent, however, to one skilled in the art, that one or more other embodiments may be practiced without some of these specific details. It should also be appreciated that reference throughout this specification to “one embodiment,” “an embodiment,” an embodiment with an indication of an ordinal number and so forth means that a particular feature, structure, or characteristic may be included in the practice of the disclosure. It should be further appreciated that in the description, various features are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of various inventive aspects, and that one or more features or specific details from one embodiment may be practiced together with one or more features or specific details from another embodiment, where appropriate, in the practice of the disclosure. 
     While the disclosure has been described in connection with what is (are) considered the exemplary embodiment(s), it is understood that this disclosure is not limited to the disclosed embodiment(s) but is intended to cover various arrangements included within the spirit and scope of the broadest interpretation so as to encompass all such modifications and equivalent arrangements.