Abstract:
An optical transceiver includes a transceiver housing configured to receive an optical sub-assembly insert. The optical sub-assembly insert includes duplex cavities configured to hold a transmit optical sub-assembly front end and a receive optical sub-assembly front end in a fixed spatial orientation for a given optical connector interface. The optical sub-assembly insert is configurable to fit inside a transceiver housing with a relatively wide range of X and Y dimensional tolerance. In one implementation, the X-Y position of the optical sub-assembly insert is dictated by the position of the transmit optical-sub assembly front end after its corresponding back end has been mounted to a heat dissipation element. Any gaps that form between the optical sub-assembly insert and the inside surface of the transceiver housing as a result of the transmit optical sub-assembly position can be accommodated with filler material.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   The present invention claims the benefit of priority to U.S. Provisional Patent Application No. 60/533,307, filed on Dec. 30, 2003, entitled “Optical Transceiver with Variably Positioned Nose Piece”, the entire contents of which are incorporated herein by reference. 

   BACKGROUND OF THE INVENTION 
   1. The Field of the Invention 
   The present invention relates generally to optical transceiver modules employed in optical communications networks. More specifically, the present invention relates to an adjustable optical transceiver design that maximizes thermal dissipation from heat-sensitive transceiver components. 
   2. Background and Relevant Art 
   Fiber optic technology is increasingly employed as a method by which information can be reliably transmitted via a communications network. Networks employing fiber optic technology are known as optical communications networks, and are marked by high bandwidth and reliable, high-speed data transmission. 
   Optical communications networks employ optical transceivers in transmitting information via the network from a transmission node to a reception node.  FIGS. 1A ,  1 B, and  2 A through  2 B illustrate conventional configurations of an optical transceiver  100 , which includes a frame, a housing  110 , and an optical sub assembly (e.g., Transmit Optical Sub-Assembly  150 ) used to transmit or receive optical information. In particular, a Transmit Optical Sub-Assembly (“TOSA”)  150  at the transmission node of an optical network receives an electrical signal from an electronic device, such as a computer, and converts the electrical signal into a corresponding optical signal. The TOSA  150  then transmits the optical signal over a fiber optic cable to a reception node of the network. 
   The transceiver  100  can also serve as a reception node on the optical network. In particular, the conventional transceiver  100  includes a Receive Optical Sub-Assembly (“ROSA”) component  155  ( FIG. 2A ), which receives the optical signal over the optical fiber, and uses, for example, a photodetector to convert the optical signal into corresponding electrical signals. The electrical signals are then forwarded to a host device, such as a computer, for processing. 
   Generally, a conventional “OSA”, a generic term for the TOSA  150  or ROSA  155 , includes a main body  183 , a nose piece  170 , and, in some cases, an alignment ridge  180  that aids the OSA physical alignment within the transceiver module  100 . A conventional transceiver  100  includes an outer housing  110  having inner walls  130 ,  140 , and an alignment ridge  120  that can be used to position the OSAs via, for example, portion  180 . The conventional transceiver walls  130 ,  140  surround one or more internal cavities, which serve as one or more fiber optic receptacles for conventional “LC” or “SC” optical connector ends. Mounted inside an assembled transceiver module  100  generally, therefore, are the TOSA  150 , ROSA  155 , and a transceiver substrate (e.g., a printed circuit board)  125 . The TOSA  150  and ROSA  155  are connected to the transceiver substrate  125  via any number of connectors, such as the illustrated flex connectors  165 . 
   Since OSA performance, in particular TOSA performance, can be affected adversely by excessive temperatures, it is important in some cases to provide adequate, reliable means to remove the heat from the TOSA and from the transceiver, generally. One way in which this is typically done with cylindrical TOSAs (e.g.,  150 ) is with a thermally conductive extension  160 , which conducts heat from the inner core of the TOSA  150  onto a separate heat dissipating element  105 . The heat dissipating element  105  in turn distributes the heat outside of the transceiver module  100 . In contrast with cylindrical TOSAs  150 , a box-shaped OSAs (not shown) disperses heat directly to the transceiver housing  110  due to surface-to-surface contact, and hence without a separate heat dispersion tongue  160 . 
   Unfortunately, some challenges arise in providing adequate TOSA heat dissipation, based at least in part on alignment procedures inherent in the manufacturing process. For example, the TOSA front end  170  (as well as the ROSA front end) is typically aligned as a separate component to the TOSA body  183 , prior to mounting the TOSA  150  to a transceiver package. Any variability, however slight, that is introduced when aligning the TOSA front end  170  to the back end  183  can make it difficult to both conduct heat out of the TOSA and at the same time ensure that the TOSA  150  and ROSA  155  are both properly aligned for a given optical cable connector interface. 
   In particular, this variability between a TOSA and ROSA in the transceiver module can pose a particular challenge for using conventional heat dissipating components (e.g.,  105 ). Generally speaking, if heat dissipating components were composed of substantially flexible materials, there would be less difficulty in aligning and fitting a given TOSA in a transceiver assembly in n appropriate position relative to the ROSA. In particular, a flexible heat dissipating component could be made somewhat larger than required, and then compressed to the appropriate fit, to ensure the TOSA and ROSA front ends are aligned with similar X and Y positioning inside the transceiver housing. Flexible materials, however, are not good thermal conductors, and therefore poor heat dissipaters. 
   On the other hand, rigid heat dissipating elements create other difficulties related to whether the TOSA and ROSA in a transceiver can be coupled with a conventional optical fiber connector interface. In short, when aligning the relevant OSA (TOSA or ROSA) front end to its respective back end, the OSA front end is often slightly offset relative to its respective OSA body by a measure of thousandths of an inch. With conventional OSAs that do not require heat dissipation, this is not ordinarily a very big problem since the front ends of each OSA are still secured (e.g., by alignment ridge  120  on the transceiver frame, and alignment ridge  180  on the OSA) in a uniform spatial position in the transceiver housing  110 . In particular, transceivers that do not require heat dissipation also allow the respective back ends of the TOSA and ROSA to vary with respect to each other. For example, the respective back ends of the TOSA and ROSA are typically connected to the transceiver substrate  125  with some sort of flexible connector, such as the illustrated flex circuit  165 , which accommodates the back end variation. 
   Unfortunately, when using a rigid heat dissipation element (e.g.,  105 ), the TOSA  150  back end can not be allowed to float freely. In particular, the TOSA  150  that implements heat dissipation also has its back end (e.g.,  183 , and conductive tongue  160 ) secured to the rigid heat dissipation element  105 . This securing of the OSA back end can cause a corresponding, slightly-offset spatial position of the TOSA front end  170  relative to the ROSA  155  front end  175  position inside the transceiver housing  110 , due to the previously described OSA alignment variations. 
   In many cases, this offset spatial position of the TOSA front end  170  is different enough from the spatial position of the ROSA front end  175  inside the transceiver housing  110  that the TOSA front end  170  and ROSA front end  175  do not adequately align with a conventional optical fiber connector. In particular, differences of thousandths of an inch in OSA alignment can cause significant stress on the transceiver when trying to get rigidly mounted parts to fit in a defined optical connector space. Such seemingly miniscule differences, which are amplified in small form factor components, can also cause failure of the optical cable to connect to the transceiver in the first instance. 
   Accordingly, an advantage in the art can be realized with optical transceivers that can dissipate heat more reliably in systems such as small form factor systems. In particular, an advantage can be realized with heat dispersion systems that dissipate heat efficiently in an optical transceiver, without significantly complicating important positioning between a TOSA and ROSA, such that the TOSA and ROSA can still readily connect to a standardized optical fiber connector. 
   BRIEF SUMMARY OF THE INVENTION 
   The present invention solves one or more of the foregoing problems in the art with an optical transceiver package that allows for efficient thermal conductivity, as well as acceptable OSA alignment within the optical transceiver receptacles. In particular, an optical transceiver in accordance with the present invention holds the TOSA and ROSA front ends in an appropriate position for an optical fiber connector, and also allows the TOSA to be secured to a rigid heat dissipating element. 
   For example, in one implementation of the present invention, an optical transceiver includes a heat dissipating element. The optical transceiver also includes an OSA insert having two OSA cavities formed therein, the cavities being configured to fit snugly about a corresponding TOSA and ROSA. The OSA insert is positioned inside the optical transceiver housing with one or more degrees of freedom, so that the OSA insert moves as the TOSA back end is moved when being mounted to the heat dissipating element. Since the OSA insert moves when the TOSA front end moves with the TOSA back end, the OSA insert preserves the ROSA front end position relative to the TOSA front end position inside the transceiver housing. This allows for effective heat dissipation in an optical transceiver without complicating important ROSA and TOSA spatial orientations for a given optical fiber connector. 
   Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by the practice of the invention. The features and advantages of the invention may be realized and obtained by means of the instruments and combinations particularly pointed out in the appended claims. These and other features of the present invention will become more fully apparent from the following description and appended claims, or may be learned by the practice of the invention as set forth hereinafter. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In order to describe the manner in which the above-recited and other advantages and features of the invention cam be obtained, a more particular description of the invention briefly described above will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings. Understanding that these drawings depict only typical embodiments of the invention and are not therefore to be considered to be limiting of its scope, the invention will be described and explained with additional specificity and detail through the use of the accompanying drawings in which: 
       FIG. 1A  illustrates a conventional optical transceiver frame and housing; 
       FIG. 1B  illustrates a conventional cylindrical OSA that is used in conjunction with the conventional optical transceiver frame and housing shown in  FIG. 1A ; 
       FIG. 2A  illustrates a perspective view of a conventional optical transceiver, having a TOSA and ROSA mounted inside the transceiver frame shown in  FIG. 1A ; 
       FIG. 2B  illustrates a side view of a conventional TOSA shown in  FIGS. 1B and 2A  when coupled to a heat dissipating element; 
       FIG. 3A  illustrates a perspective view of an optical transceiver in accordance with an implementation of the present invention, in which a TOSA and ROSA are mounted inside an optical transceiver frame and housing via an OSA insert; 
       FIG. 3B  illustrates a perspective view of the TOSA and ROSA when mounted inside the OSA insert, but removed from the transceiver frame and housing; 
       FIG. 3C  illustrates a facing view of the TOSA and ROSA shown in  FIG. 3B ; 
       FIG. 4A  illustrates a side view of the optical transceiver shown in  FIG. 3A , in which a TOSA that is assembled with one alignment variation is mounted to a heat dissipating element; and 
       FIG. 4B  illustrates a side view of the optical transceiver shown in  FIG. 4A , in which a TOSA assembled with another alignment variation is mounted to the heat dissipating element. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The present invention extends to an optical transceiver package that allows for efficient thermal conductivity, as well as acceptable OSA alignment within the optical transceiver receptacles. In particular, an optical transceiver in accordance with the present invention holds the TOSA and ROSA front ends in an appropriate position for an optical fiber connector, and also allows the TOSA to be secured to a rigid heat dissipating element. 
   For example,  FIG. 3A  illustrates an implementation of the present invention in which an optical transceiver  200  comprises a duplex OSA insert  235  positioned within a transceiver housing  210 . In general, the OSA insert  235  can be formed from any number of materials, including metal, metal alloys, plastic, and or ceramic materials. In one implementation, for example, the OSA insert  235  comprises a plastic material, which is configured with several mils of tolerance in any X or Y orientation inside optical transceiver housing  210 . The OSA may also be surrounded by one or more joints, shims, ribs, or the like, which are easily configured to fit the OSA insert  235  inside the transceiver housing  210 . In one implementation, the joints, shim, ribs, or the like are also thermally conductive. 
   In one implementation, an optical transceiver housing  210  includes housing walls that are about 20 mils thick (1 “mil” is about 1 thousandth of an inch), and that form a gap of about 10 mils between the OSA insert  235  ( FIG. 3B ) walls, which are also about 20 mils thick. An approximately 10 mil gap such as this can allow the OSA insert  235  to be variably positioned inside the optical transceiver housing  210 . 
     FIG. 3A  also shows that the OSA insert  235  is formed with cavities  243  and  245 , as well as corresponding mounting gaps  232 , which accommodate a conventional optical LC fiber connector. One will appreciate, however, that the LC connector is only one type of connector that can be used in accordance with the present invention, and that the OSA insert  235  can also be configured for other types of optical fiber connection interfaces, such as an SC, or other similar optical connector interface. The illustrated LC connector configuration, therefore, is shown primarily for purposes of convenience. In any event,  FIGS. 3A and 3B  show that the optical connector interface is formed primarily in the OSA insert  235  cavities  243 ,  245 , rather than necessarily in the transceiver housing  210 . 
     FIGS. 3A ,  3 B, and  3 C show that the optical transceiver  200  also includes a TOSA  250  having at least a portion (e.g., front end  270 ) of the TOSA being inserted snugly inside cavity  243  of the OSA insert  235 , and a ROSA  255 , which has at least a portion (e.g., front end  275 ) of the ROSA  255  inserted snugly inside cavity  245 . These illustrated snug fits accomplish one or more of any number of ends. For example, the cavities  243  and  245  are configured to help define an X-Y spatial orientation of the TOSA  250  front end  270  relative to the ROSA  255  front end  275 , so that the respective TOSA and ROSA front ends are suitably positioned to interface with a given optical connector. Furthermore, the snug fit of the OSA insert  235  around the TOSA  250  front end  270  and ROSA  255  front end  275  provides that movement of one of the OSA back ends (e.g.,  260 ) results in a corresponding movement of the other of the OSAs, thereby preserving the TOSA to ROSA front end orientation in a number of positions of the OSA insert  235 . 
   As shown in  FIGS. 3A through 3C , for example, the OSA insert  235  comprises one or more ribs  237  that help position the OSA insert  235  within varying degrees of tolerance inside the transceiver housing  210 . In one implementation, the illustrated ribs  237  not only provide a degree of alignment tolerance inside the transceiver housing  210 , but can also provide one or more thermal contact points between the OSA insert  235  and the inside surface of the transceiver housing  210 . Thus, the OSA insert  235  can comprise materials and conformations that make one or more implementations of the OSA insert  235  ideal for dissipating an amount of heat. 
   In addition, since the OSA insert  235  can be positioned with varying degrees of freedom along the X and Y axis inside the transceiver housing  210 , the TOSA  250  can be mounted to rigid heat dissipating elements  205  without adversely affecting front end alignment. In particular, the configurable OSA insert  235  can be particularly useful where variations between the TOSA front end  270  are fairly distinct relative to the back end  283 . For example, a TOSA  250  front end  270  alignment that varies by, for example, 2 mils, relative to the TOSA  250  back end  283  will have a different spatial position at the front end  270  inside the transceiver housing  210  compared with a TOSA  250  that has a front end  270  that varies by more or less than this with respect to its back end  283 . Thus, the variation in alignment of a specific TOSA&#39;s front end  270  with respect the TOSA&#39;s back end  283  at least partly drives the position of the relevant OSA insert  235 , and hence the corresponding ROSA  255  front end  275  position inside the transceiver housing  210 . 
   The heat dissipating elements  205  described herein can comprise any number of thermally-conductive materials, including thermally-conductive metals such as copper or aluminum. There are, of course, a wide range of thermally-conductive elements that may be useful for heat dissipating element  205 , including thermally conductive plastics and ceramics, although copper and aluminum are generally more available. Furthermore, appropriate heat dissipation can be produced in materials that not only conduct heat, but also provide different degrees of electrical conduction (or lack thereof). Of course, metals such as copper and aluminum are typically good conductors of both heat and electricity. Some other materials, however, such as an aluminum nitrite ceramic may be a good conductor of heat, but a poor conductor of electricity. Accordingly, a manufacturer can adjust the materials used as the heat dissipating element  205  for a wide variety of implementations. 
   The apparatus described herein, therefore, provide a degree of flexibility in assembling an optical transceiver  200 . For example, in one implementation of an optical transceiver  200  assembly, the front ends  270  and  275  of the respectively assembled TOSA  250  and ROSA  255  are each inserted in a corresponding cavity  243  and  245  of an OSA insert  235 . The OSA insert  235  is then configured or adjusted to fit inside the transceiver housing  210  within a few mils of alignment tolerance. For example, the manufacturer can shave off one or more ribs  237  so that the thermally-conductive TOSA tongue  260  is able to abut the heat dissipation element  205  directly. The manufacturer can then position the OSA insert  235  inside the optical transceiver housing  210 . 
   In another implementation, the OSA insert  235  is already fitted inside the transceiver housing  210  within an acceptable degree of tolerance, and the respective front ends  270  and  275  of the TOSA  250  and ROSA  255  are then inserted into the appropriate cavity. In any event, the manufacturer then mounts the TOSA  250  to the heat dissipating element  205 . In one implementation, for example, the manufacture mounts the TOSA  250  by positioning a thermally-conductive tongue  260  of the TOSA  250  about the heat dissipation element  205 . The manufacturer can then secure the tongue  260  to the heat dissipating element  205  using a chemical bond (e.g., an adhesive between the tongue  260  and the element  205 ), or using a mechanical bond (e.g., a clamp and screw about the tongue  260  and the element  205 ), and/or any combination thereof. The type of chemical or mechanical bonding means can be chosen based on any number of properties, such as bonding strength, as well as thermal conductivity properties. 
   The positioning of the tongue  260  about the heat dissipating element  205  may cause the manufacturer to further adjust the OSA insert  235  position inside the transceiver housing  200  to accommodate some other variability. In any case, this and/or any prior X/Y adjustments can cause a fairly significant gap between at least one side of the OSA insert  235  and an inside surface of the transceiver housing  210 . Accordingly, in one implementation, the manufacturer can further insert filler materials (e.g.,  FIG. 4B , filler  280 ) to substantially close any gap between the OSA insert  235  and the corresponding inside surface of the transceiver housing  210 . In one implementation, appropriate filter materials  280  include shims or adhesives, although any number or type of filler materials  280  may be consistent with the principles described herein. 
   Once the OSA insert  235  is appropriately positioned, the TOSA  250  and ROSA  255  can be electrically coupled to a corresponding transceiver substrate  225 , which includes one or more circuitry components for driving the TOSA or ROSA, and passing signals to and from an electronic device. The TOSA  250  and ROSA  255  can be electrically coupled to the transceiver substrate  225  using any number of coupling means, including, for example, use of a flex circuit, or a plug connector. In one implementation, the ROSA  255  is electrically coupled to the transceiver substrate  225  using a flex circuit, while the TOSA  250  is electrically coupled to the transceiver substrate  225  via circuit traces on the tongue  260 , which are, in turn, coupled to circuitry on the transceiver substrate. Any number and/or combination of electrical coupling methods, however, can be appropriate in accordance with the concepts presented herein. 
     FIGS. 4A and 4B  show alternate side views of the transceiver  200 , in which the TOSA  250  with one alignment variation between the TOSA front end  270  and back end  283  is mounted to a heat dissipation element  205 . In particular,  FIGS. 4A and 4B  show alignment variations in which the TOSA front end  270  is offset in one or more vertical positions relative to the vertical position of the TOSA back end  283 . One will appreciate, however, that horizontal alignment variations (not shown), as well as other alignment variations in the X/Y plane may also be possible, which ultimately effect the positioning of the OSA insert  235  inside the transceiver housing  210 . As such, the alignment variations of  FIGS. 4A and 4B  are merely exemplary. In any event,  FIG. 4A  shows that when the TOSA  250  tongue  260  is mounted to a heat dissipation element  205 , the corresponding front end  270  shifts the OSA insert  235  inside the transceiver housing  210  in one direction. Accordingly, significant gaps that form between the transceiver housing  210  and the OSA insert  235  are filled with filler materials  280 . 
     FIG. 4B  shows that another TOSA  250  having a different alignment variation, compared with the TOSA in  FIG. 4A , is mounted to heat dissipating element  205 . The mounting of the tongue  260  in  FIG. 4B  causes a certain positioning of the TOSA front end  270 , which causes a different positioning of the OSA insert  235  relative to the transceiver housing  210 . In particular,  FIG. 4B  shows that the ribs  237  on the bottom of the OSA insert are shaved away (e.g., using a jig, or other appropriate tool), such that the OSA insert  237  is closer to one inside surface of the transceiver housing  210 . This adjustment of the OSA insert  237  allows the TOSA tongue  260  to abut the heat dissipation element  205  in a substantially flush fashion. As previously described, the resulting gap between the upper end of the OSA insert  235  and the inside surface of the transceiver housing  210  can be filled with a filler material  280 , in order to accommodate the closer proximity of the lower end of the OSA insert  235  relative to the transceiver housing  210 . 
   Accordingly, implementations of the OSA insert  235  accommodate spatial variations that occur due to alignment variations between an OSA front end and back end. In particular, implementations of the present invention can accommodate several mils of front end  270  spatial variation, and at the same time ensure that the ROSA  255  and TOSA  250  are still aligned appropriately for the given optical connection interface. 
   The apparatus described herein has also been described primarily as a means for enabling the thermal coupling of a TOSA  250  to a heat dissipation element  205 . One will appreciate, however, that the OSA insert  235  has a number of advantages by itself, such as that the OSA insert  235  can be shaped, adjusted, or modified in any number of ways, and still maintain an appropriate TOSA  250  and ROSA  255  alignment for any given optical connector interface. In particular, since the OSA insert  235  can be manufactured from a variety of thermally-conductive materials, a manufacturer may simply avoid the heat dissipation element  205  altogether in certain transceiver modules in lieu of the thermal-conductivity properties of the OSA insert  235 . Accordingly, the transceiver apparatus and components in accordance with the present invention provide a wide variety of manufacturing options and advantages pursuant to creating thermally-efficient optical transceivers. 
   The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.