Patent Publication Number: US-2022221668-A1

Title: Apparatus And Method For Thermal Dissipation Of Photonic Transceiving Module

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present disclosure is a continuation of U.S. patent application Ser. No. 17/095,269, filed on Nov. 11, 2020, which is a continuation of U.S. patent application Ser. No. 16/578,090 (now U.S. Pat. No. 10,942,323), filed on Sep. 20, 2019. The entire disclosures of the applications referenced above are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     The present disclosure is related to a photonics technology, more particularly, to an apparatus and a method for efficient thermal dissipation of a photonic transceiver module. 
     As science and technology are progressing rapidly, processing speed and capacity of the computer increase correspondingly. The communication transmission or reception using the traditional cable is limited to bandwidth and transmission speed of the traditional cable, but the mass information transmission required in modern life causes the traditional communication transmission overload. To address such requirements, the optical fiber transmission system replaces the traditional communication transmission system gradually. The optical fiber transmission system does not have bandwidth limitation, and also has advantages of high-speed data transmission, long transmission distance, its material is impervious to electromagnetic waves. Therefore, the electronics industry performs research toward optical fiber transmission which will become the mainstream in the future. Said optical communication is a technology in that light waves function as signal carriers and transmitted between two nodes via the optical fiber. Field of optical communication can be divided into optical communication side and electric communication side according to transmission medium. By the optical transceiver, the received optical signal can be converted to an electrical signal capable of being processed by an IC, or the processed electrical signal can be converted to the optical signal to be transmitted via optical fiber. Therefore, objective of communication can be achieved. 
     The high-speed data transmission needs high-performance photonic transceiver which needs high efficiency heat dissipation during its operation. For example, a latest QSFP-DD transceiver module expects to multi-fold of heat dissipation function over a module package size only 20% bigger. Therefore, it is desired to have an improved apparatus for efficiently dissipating heat from a package of a photonic transceiver module. 
     BRIEF SUMMARY OF THE INVENTION 
     The present disclosure is related to a photonics technology, more particularly, to an apparatus and a method for efficiently dissipating heat away from a package of a photonic transceiver module. In certain embodiments, the invention is applied for high bandwidth optical communication, though other applications are possible. 
     In modern electrical interconnect systems, high-speed serial links have replaced parallel data buses, and serial link speed is rapidly increasing due to the evolution of CMOS technology. Internet bandwidth doubles almost every two years following Moore&#39;s Law. But Moore&#39;s Law is coming to an end in the next decade. Standard CMOS silicon transistors will stop scaling around 5 nm. And the internet bandwidth increasing due to process scaling will plateau. But Internet and mobile applications continuously demand a huge amount of bandwidth for transferring photo, video, music, and other multimedia files. This disclosure describes techniques and methods to improve the communication bandwidth beyond Moore&#39;s law. 
     Serial link performance is limited by the channel electrical bandwidth and the electronic components. In order to resolve the inter-symbol interference (ISI) problems caused by bandwidth limitations, we need to bring all electrical components as close as possible to reduce the distance or channel length among them. Stacking chips into so-called 3-D ICs promises a one-time boost in their capabilities, but it&#39;s very expensive. Another way to achieve this goal in this disclosure is to use multiple chip module technology. 
     In an example, an alternative method to increase the bandwidth is to move the optical devices close to electrical device. Silicon photonics is an important technology for moving optics closer to silicon. In this patent application, we will disclose a high-speed electrical optics multiple chip module device to achieve terabits per second speed, as well as variations thereof. Silicon photonics has led to development of compact packages of photonic transceiver modules in many pluggable specifications. Yet, the compact package of powerful photonic transceiver module needs innovated design for efficiently dissipating heat away during its operation. 
     In a specific embodiment, the present disclosure provides an apparatus for dissipating heat from a photonic transceiver module. The apparatus includes a top-plate member disposed in a length direction of a package for the photonic transceiver module. Additionally, the apparatus includes multiple fins with one length formed on the top-plate member along the length direction from a backend position near middle of the top-plate member to a frontend position except that an elongated void is formed from the backend position of the multiple fins to one backend of at least one fin with a shorter length. Furthermore, the apparatus includes a cover member disposed over the multiple fins with a horizontal sheet, two vertical side sheets, and a flange bent vertically from a middle portion of a backend of the horizontal sheet. Moreover, the apparatus includes a spring loaded in the elongated void between the flange and the one backend of the at least one fin for naturally pushing the cover member to slide backward beyond the backend position of the multiple fins until the backend of the horizontal sheet is stopped against an object. 
     In another aspect; the present disclosure provides a method of dissipating heat from a package of a photonic transceiver module. The method includes a step of setting a top-plate member disposed in a length direction of the package. Additionally, the method includes forming multiple fins of one length on the top-plate member along the length direction from a backend position near middle of the top-plate member to a frontend position except an elongated void being formed from the backend position of the multiple fins to one backend of at least one fin with a shorter length. Furthermore, the method includes disposing a cover member over the multiple fins with a horizontal sheet, two vertical side sheets, and a flange bent vertically from a middle portion of a backend of the horizontal sheet. Moreover, the method includes loading a spring in the elongated void between the flange and the one backend of the at least one fin for naturally pushing the cover member backward beyond the backend position of the multiple fins until the backend of the horizontal sheet is stopped against an object. 
     In yet another aspect, the present disclosure provides a package structure for a photonic transceiver module comprising an apparatus of claim  1  for dissipating heat up to 20 W therefrom. 
     The present invention achieves these benefits and others in the context of known technology. However, a further understanding of the nature and advantages of the present invention may be realized by reference to the latter portions of the specification and attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The following diagrams are merely examples, which should not unduly limit the scope of the claims herein. One of ordinary skill in the art would recognize many other variations, modifications, and alternatives. It is also understood that the examples and embodiments described herein are for illustrative purposes only and that various modifications or changes in light thereof will be suggested to persons skilled in the art and are to be included within the spirit and purview of this process and scope of the appended claims. 
         FIG. 1  is a side view of a photonic transceiver module with external heat sink plugged into a custom system equipment according to an embodiment of the present invention. 
         FIG. 2  shows both a top view and a side view of an external heat sink photonic transceiver package structure with lid according to the embodiment of the present invention. 
         FIG. 3  is a perspective exploded view of an external heat sink formed on a package of a photonic transceiver module according to an embodiment of the present invention. 
         FIG. 4A  is a perspective top view of a cover member of the external heat sink of  FIG. 3  according to the embodiment of the present invention. 
         FIG. 4B  is a perspective bottom view of the cover member and a loaded spring of the external heat sink of  FIG. 3  according to the embodiment of the present invention. 
         FIG. 5  is a perspective view of a photonic transceiver module having a fixed external heat sink plugged into a custom system having an internal thermal dissipation equipment according to an embodiment of the present invention. 
         FIG. 6A  is a side view of the external heat sink of  FIG. 5  with a cover member being at a position separated by an air gap from a face plate of the internal thermal dissipation equipment according to the embodiment of the present invention. 
         FIG. 6B  is a side view of the external heat sink of  FIG. 5  with a cover member being at a position with a minimized air gap from the face plate of the internal thermal dissipation equipment according to the embodiment of the present invention. 
         FIG. 6C  is a cross-section view of the external heat sink of  FIG. 6B  with a cover member being pushed by the loaded spring to the position with the minimized air gap from the face plate of the internal thermal dissipation equipment according to the embodiment of the present invention. 
         FIG. 7  is a flow chart illustrating a method of thermal dissipation for a package of a photonic transceiver module according to an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present disclosure is related to a photonics technology, more particularly, to an apparatus and a method for efficiently dissipating heat away from a package of a photonic transceiver module. In certain embodiments, the invention is applied for high bandwidth optical communication, though other applications are possible. 
     The following description is presented to enable one of ordinary skill in the art to make and use the invention and to incorporate it in the context of particular applications. Various modifications, as well as a variety of uses in different applications will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to a wide range of embodiments. Thus, the present invention is not intended to be limited to the embodiments presented, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein. 
     In the following detailed description, numerous specific details are set forth in order to provide a more thorough understanding of the present invention. However, it will be apparent to one skilled in the art that the present invention may be practiced without necessarily being limited to these specific details. In other instances, well-known structures and devices are shown in block diagram form, rather than in detail, in order to avoid obscuring the present invention. 
     The reader&#39;s attention is directed to all papers and documents which are filed concurrently with this specification and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference. All the features disclosed in this specification, (including any accompanying claims, abstract, and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features. 
     Furthermore, any element in a claim that does not explicitly state “means for” performing a specified function, or “step for” performing a specific function, is not to be interpreted as a “means” or “step” clause as specified in 35 U.S.C. Section 112, Paragraph 6. In particular, the use of “step of” or “act of” in the Claims herein is not intended to invoke the provisions of 35 U.S.C. 112, Paragraph 6. 
     Please note, if used, the labels left, right, front, back, top, bottom, horizontal, vertical, side, inner face, outer face, forward, reverse, clockwise and counter-clockwise have been used for convenience purposes only and are not intended to imply any particular fixed direction. Instead, they are used to reflect relative locations and/or directions between various portions of an object. 
       FIG. 1  is a side view of a photonic transceiver module with external heat sink plugged into a custom system equipment according to an embodiment of the present invention. The photonic transceiver module has been developed very fast in resent years to provide high data rates of 4×10 Gbit/s, 4×28 Gbit/s or higher for high-speed data communications applications. The photonic transceiver module is also characterized by its small form factor pluggable package structure. For example, As shown, the package structure is compatible with the Quad Small Form-factor Pluggable (QSFP) specification, or Quad Small Form-factor Pluggable Double-Density (QSFP-DD) specification, or latest Quad Small Form-factor Pluggable Double-Density Type II (QSFP-DD Type 2) specification. With high data rate being provided, higher laser power and higher frequency may be involved, yielding more heat during its operation. Thermal dissipation of the heat generated by the photonics transceiver modules has become a key focus for new module mechanical design. Past designs only had to dissipate 2-4 W of power, but the state-of-art modules are expected to dissipate up to 20 W in a package that is only 25% larger in size than past design. 
     Referring to  FIG. 1 , using the QSFP-DD module as an example, the package  100  (of the photonics transceiver module) usually is coupled with an internally air-cooled thermal sink  300  associated with customer network system frame for heat dissipation. Because of the higher thermal load of newer modules in the QSFP-DD specification, an external thermal sink  200  fixed to a top-plate member of the package  100  has been proposed for added cooling efficiency. The external thermal sink  200  is integrated on the top-plate member along a length direction from a first position at a frontend of the package  100  to a second position near middle region of the top-plate member. The external thermal sink  200  has a fixed cover over multiple fins, all having a length of L, to form multiple air-flow channels in gaps between neighboring fins under the cover. As the photonics transceiver module is plugged to the network system frame, the second position of the external heat sink  200  must be set just outside a bezel face plate  301  of the internally air-cooled thermal sink  300 . The bezel face plate  301  has been configured to have multiple through-holes. As air is pulled by a fan from the internally air-cooled thermal sink  300  inside a customer system frame, air is assumed to be pulled through the air-flow channels in the integrated external thermal sink  200  to help dissipate heat on the front of the photonics transceiver module. 
       FIG. 2  shows both a top view and a side view of an external heat sink photonic transceiver package structure with lid according to the embodiment of the present invention. Referring to  FIG. 1  and  FIG. 2 , the second position of the external heat sink is a backend position of the cover as well as the multiple fins of the length L. Due to mechanical tolerancing of the face plate  301  of the internally air-cooled thermal sink  300  on its thickness and position relative to system frame, the backend position of the cover of the external heat sink  200  must be limited with a nominal gap G of about 1 (or 2) mm from the customer bezel face plate  301 . Because of this gap, pulling air over the multiple fins of the external heat sink  200  is like having a hole in a straw, where the air flow will be greatly reduced to impact thermal dissipation. 
     In some implementations, referring to  FIG. 1 , the face plate design of the customer system frame includes an EMI finger  302  disposed in between. In such a configuration, a first photonics transceiver module package  100 A is plugged in at a higher position with a first external heat sink  200 A facing a face plate  301  and a second photonics transceiver module package  100 B is plugged at a lower position with a second external heat sink  200 B facing an end face of EMI finger  302 . Again, the mechanical tolerance requires a first gap G to be existed between the backend of the first external heat sink  200 A and the face plate  301  and a second gap G′ between the backend of the second external heat sink  200 B and the end face of the EMI finger  302 . For both plugged-in packages  200 A and  200 B of the photonics transceiver modules, the gap G and G′ make the air-flow channels less ideal in respective two situations. 
       FIG. 3  is a perspective exploded view of an external heat sink formed on a package of a photonic transceiver module according to an embodiment of the present invention. Referring to  FIG. 3 , the external heat sink is configured with multiple fins  201  formed vertically on the top-plate member  101  of the package  100  of the photonics transceiver module. In the embodiment, the external heat sink with the multiple fins is formed in region near front end  111  of the package  100 . Optionally, a backend region of the package  100  includes electrical connector pins pf the photonics transceiver module for connecting with network system equipment on the other side of the face plate  301  of custom system frame (see  FIG. 1 ). Optionally, the fins are equally separated by a gap distance. All except at least one ( 203 ) of the multiple fins  201  have one height above the top-plate member  101  and one length from a first position (front end  202   a ) to a second position (backend  202   b ). The at least one fin is shorter in length with its backend  207   b  in a retracted position relative to the backend  202   b  of all rest fins  201 , forming an elongated void  203   c  from the backend  202   b  of all rest fins  201  to the  203   b  of the at least one fin  203  with a width of two gap distances. Additionally, the multiple fins  201  include two out-most fins with a first fin  204  fixed at a first edge position (fully visible in  FIG. 3 ) and a last fin  205  fixed at a last edge position (partially visible in  FIG. 3 ). Each of these out-most fins is configured with two notches, e.g.,  206   a  and  206   b , on the outer face of the first fin  204 . The notches on the outer face of the last fin  205  is not directly visible in  FIG. 3 . 
       FIG. 4A  is a perspective top view of a cover member of the external heat sink of  FIG. 3  according to the embodiment of the present invention.  FIG. 4B  is a perspective bottom view of the cover member and a loaded spring of the external heat sink of  FIG. 3  according to the embodiment of the present invention. Referring to  FIG. 4A ,  FIG. 4B , as well as  FIG. 3  shown before, the external heat sink includes a cover member  210  configured to cover the entire multiple fins  201  and a spring  220  configured to be loaded under the cover member  210  into the elongated void  203   c . The cover member  210  further is characterized by a rectangular shaped horizontal sheet  211  with a front end  212   a  and a backend  212   b  along its length direction, two vertical side sheets  214  and  215  connected (along downward direction) to two length edges of the horizontal sheet  211 . Each of the two vertical side sheets is configured with two slots e.g.,  216   a  and  216   b  for side sheet  214 , positioned to fit with the two notches, e.g.,  206   a  and  206   b , on the corresponding first out-most fin  204  (or the last out-most fin  205 ) for at least partially lock the cover member  210  substantially entirely over the multiple fins. Each slot  216   a  or  216   b  is made with extra free length of a few mini-meters to allow the cover member  210  to be laterally moveable along the length direction while being partially locked with fins (particularly two out-most fins  204  and  205 ) by the notches in slots. Furthermore, the cover member  210  also includes a vertical flange  213  being set to bent from a middle part of the backend  215  of the cover member  210 . Optionally, the vertically flange is positioned corresponding to the elongated void  203   c . In the embodiment, the spring  220  is loaded in the elongated void  203   c  and stopped between the vertical flange  213  and the backend  207   b  of the at least one fin  203  in shorter length as the cover member  210  is disposed to cover the multiple fins  201 . The spring  211  naturally push the cover member  210  backward as it is slide up to the extra free space provided with the two slots ( 216   a  and  216   b ) of each (e.g.,  214 ) of two vertical side sheets respectively with two notches ( 206   a  and  206   b ) being locked therein. 
     In addition to the exploded view of the package  100  of the photonics transceiver module with a fixed external heat sink  200  (cover member  210 , spring  220 , and multiple fins  201  fixed to the package  100 ),  FIG. 5  shows a photonic transceiver module having the fixed external heat sink being plugged into an internal thermal dissipation equipment of a custom system frame according to an embodiment of the present invention. Referring to  FIG. 5 , the internal thermal dissipation equipment  400  is configured with an air-cooled heat sink coupled to an electric-power fan  420  at its backend and a face plate  410  with multiple through-holes at its front end. The fan  420  draws an air flow through air-flow channels formed between gaps between the multiple fins under the cover member to dissipate heat from the front end of the photonics transceiver module into the internal thermal dissipation equipment  400 . As the photonics transceiver module is plugged in with its backend being inserted fully inside the internal thermal dissipation equipment  400 , the backend of the external heat sink  200  is designed to be left outside but substantially close to the face plate  411  except a nominal gap for room of mechanical tolerance of the internal thermal dissipation equipment  400 . Typically, this nominal gap is limited to about 1 millimeter. As described earlier in  FIG. 3 ,  FIG. 4A , and  FIG. 4B , the cover member ( 210 ) is designed to be pushed by the loaded spring  220  to slide along the length direction relative to the fixed fins ( 201 ,  204 ,  203 ,  205 ), provided with the extra free distance of the slot (e.g.,  216   a ) relative to the size of the notch (e.g.,  206   a ). When the extra free distance is set to be at least larger than the nominal gap, the backend ( 211 ) of the cover member  210  is naturally pushed by the loaded spring  220  to touch the face plate  411 , thus closing or at least minimizing the gap. Optionally, the nominal gap is about 1 millimeter and the extra free distance of the slot versus the notch can be set to be 2 or more millimeters. 
       FIG. 6A  is a side view of the external heat sink of  FIG. 5  with a cover member being at a position separated by an air gap from a face plate of the internal thermal dissipation equipment according to the embodiment of the present invention. Referring to  FIG. 6A , this is a plugged-in configuration of the package  100  of photonics transceiver module with a fixed external heat sink  200 . This configuration is substantially same as related art where there is an air gap G&gt;0 from the backend of the cover member  210  of the external heat sink  200  to a face plate  410  of the internal thermal dissipation equipment  400 . This gap G is intentionally left by design due to manufacture tolerance of the internal thermal dissipation equipment  400 . As seen, the cover member  210  is disposed with the two notches  206   a  and  206   b  fit in the corresponding two slots  216   a  and  216   b  on the outer face of the out-most fin ( 204 ). The package  100  is in a plugged-in position in association with the internal thermal dissipation equipment  400 . The air gap G&gt;0 causes reduced efficiency in thermal dissipation of the external heat sink  200 . 
       FIG. 6B  is a side view of the external heat sink of  FIG. 5  with a cover member being at a position with minimized air gap from the face plate of the internal thermal dissipation equipment according to the embodiment of the present invention. Referring to  FIG. 6B , this is substantially the same plugged-in position associated with the external heat sink  200  versus the face plate  410  of the internal thermal dissipation equipment  400  but with an air gap G˜0. The backend ( 212   b ) of the cover member  210  slides as indicated to touch the face plate  410 , making the air gap G minimized to reduce loss of air flow and improve thermal dissipation efficiency.  FIG. 6C  shows a cross-section view of the external heat sink of  FIG. 6B . This clearly illustrates the function of the loaded spring  210  under the a cover member (stopped between the vertical flange ( 213 ) and the backend ( 207   b ) of the at least one fin ( 203 ) for naturally pushing the backend ( 212   b ) of the cover member  210  to be against the face plate  410  to minimize the air gap G (˜0). 
     As shown in  FIG. 6B  and  FIG. 6C  in the side views, the horizontal sheet of the cover member ( 211 ) is disposed on top ridges of multiple fins and has a same leveled backend with vertical side sheets. The cover member and the multiple fins together form multiple air flow channels in the gaps between neighboring fins to become effective external heat sink for pulling heat of the package through the air flow channels into the internal thermal dissipation equipment. As the backend of the cover member, for both horizontal sheet and two vertical sheets, touches the face plate of the internal thermal dissipation equipment, the nominal gap there left due to mechanical tolerance can be closed or at least minimized. The minimized air gap between the backend of the cover member and the face plate of the internal thermal dissipation equipment substantially enhance heat dissipation efficiency. Optionally, the external heat sink as formed in the embodiment described herein can effectively dissipate heat over 20 W from the front end region of the photonics transceiver module. 
     In another aspect, the present disclosure provides a package for a compact photonics transceiver module. The package includes an external heat sink described herein to pull air flow therefrom for dissipating heat up to 20 W out of the front region of the photonics transceiver module. The package is a compact and pluggable type configured to in Quad Small Form-Factor Pluggable (QSFP) specification. Alternatively, the package is a compact and pluggable type configured to in Quad Small Form-Factor Pluggable Double Density (QSFP-DD) specification. Optionally, the package is a compact and pluggable type configured to in Quad Small Form-Factor Pluggable Double Density Type II (QSFP-DD type 2) specification. 
     In yet another aspect, the present disclosure provides a method of dissipating heat out of a package of a photonic transceiver module, especially for high-power photonics transceiver module in compact form factor for high-speed data communication.  FIG. 7  shows a flow chart illustrating a method of thermal dissipation for a package of a photonic transceiver module according to an embodiment of the present invention. Referring to  FIG. 7  and further referring to  FIG. 3 ,  FIG. 6B  and  FIG. 6C , the method is implemented through an apparatus described herein for dissipating heat up to 20 W out of front region of the package of photonics transceiver module. In the embodiment, the method includes a step of setting a top-plate member disposed in a length direction. Particularly, the method employs an apparatus for dissipating heat out of the package (such as one in QSFP-DD specification) of the photonics transceiver module. 
     Additionally, the method includes a step of forming multiple fins of one length on the top-plate member along the length direction from a backend position near middle of the top-plate member to a frontend position except an elongated void being formed from the backend position of the multiple fins to one backend of at least one fin with a shorter length. The multiple fins fixed vertically on the top-plate member to become parts of an external heat sink located near front end region of the package. Optionally, all fins including the at least one fin with the shorter length has a same height and equal separation (gap) from its neighboring fins. Optionally, all fins including the at least one fin with the shorter length have a leveled front end at a first position on the top-plate member near the front end of the package. Optionally, all fins except the at least one fin with the shorter length have a leveled backend at a second position near middle region of the package. Optionally, each of the two out-most fins (the first fin and the last fin) has two notches formed on its outer face separated with a spacing in the length direction. 
     Furthermore, the method includes a step of disposing a cover member over the multiple fins with a horizontal sheet, two vertical side sheets, and a flange bent vertically from a middle portion of a backend of the horizontal sheet. In the embodiment the cover member described here is another part of the external heat sink. Optionally, the horizontal sheet of the cover member is a rectangular shape having a length at least longer than the length of the fins. Optionally, the two vertical side sheets are bent from two opposed side edges of the horizontal sheet and have a same length as that of the horizontal sheet and a same (or larger) height as (than) the height of the fins. Each of the two vertical side sheets is configured to have two slots formed in respective position for the two notches on the outer face of the out-most fin to fit in while with extra free spacing in the length direction. Optionally, the flange is substantially aligned with the elongated void to face the backend of the at least one fin with the shorter length. As the cover member is disposed in position, the horizontal sheet is in touch with top ridges of all fins and the slots on the two vertical side sheets take the notches to partially lock the cover member with the fins. Optionally, the flange is substantially aligned with the elongated void to face the backend of the at least one fin with the shorter length as the cover member is disposed in the position described above. 
     Moreover, the method including loading a spring into the elongated void while disposing the cover member into the position over the multiple fins and having the notches partially being locked by the slots. The loaded spring is stopped between the flange and the backend of the at least one fin with the shorter length. Naturally, the loaded spring pushes the cover member to be movable laterally along the length direction allowed by the extra free spacing set for the slots. The backend of the cover member is able to slide backward. Provided that the extra free spacing is larger than a designed nominal gap of about 1 mm to a system frame in which the package of the photonics transceiver module is plugged, the backend of the cover member is naturally in touch with a face plate of the system frame (in some embodiments, it is an internal thermal dissipation equipment associated with a custom network system). In other words, the step of the method naturally close or at least minimize an air gap caused by the designed nominal gap that results in leak of air flow in the multiple air flow channels of the external heat sink. As the result, the heat dissipation efficiency of the external heat sink is substantially enhanced. Optionally, the method is have the external heat sink described above to effectively dissipate heat up to 20 W away from the front end region of the photonics transceiver module. 
     While the above is a full description of the specific embodiments, various modifications, alternative constructions and equivalents may be used. Therefore, the above description and illustrations should not be taken as limiting the scope of the present invention which is defined by the appended claims.