Abstract:
An optical transceiver that provides an inner metal cover in addition to a metal cover and a frame is disclosed. The inner cover includes a ceiling, a front skirt bent downward at a front edge of the ceiling, sides bent downward at both side edges of the ceiling, and a pair of arms extending rearward from respective side ends of the ceiling. The ceiling makes an obtuse angle with respect to the front skirt when the arms are not assembled with the frame, and shapes in convex protruding outward when the metal cover is not assembled with frame and. Assembling the inner cover and the metal cover with the frame, the inner cover comes in securely contact with the metal cover.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to an optical transceiver, in particular, the invention relates to an optical transceiver that enhances the EMI shielding. 
         [0003]    2. Related Prior Art 
         [0004]    One type of the optical transceiver is well known and called as the hot pluggable optical transceiver, in which the transceiver is set within a cage prepared in the host system without turning off the power supply of the system. Such an optical transceiver provides an electrical plug in the rear end thereof, which is mated with the electrical connector prepared in the deep end of the cage; thus the communication between the optical transceiver and the host system may be established. The optical transceiver also provides an optical receptacle in the front end thereof, into which an external optical connector may be inserted. The United States Patent issued as U.S. Pat. No. 7,416,353 has disclosed such optical transceiver. The EMI shielding becomes further important as the operational speed of the optical transceiver reaches and sometimes exceeds 10 GHz. 
       SUMMARY OF THE INVENTION 
       [0005]    The optical transceiver according to one aspect of the present invention comprises an optical subassembly (hereafter denoted as OSA), an optical receptacle, a frame, an inner cover, and a metal cover. The OSA includes a sleeve and a package. The optical receptacle receives an external optical connector that secures an optical fiber optically coupled with the optical subassembly. The frame provides a bottom to mount the package of the optical subassembly and side walls each rising from respective edges of the bottom. The inner cover, which is made of metal, includes a ceiling that extends between the side walls of the frame and covers the housing of the optical subassembly. The metal cover, which is assembled with the frame, covers and comes in contact to the inner cover, One feature of the optical transceiver of the present invention is that the ceiling of the inner cover shapes in convex, that is, it protrudes outward between the side walls when the metal cover is not assembled with the frame, and the metal cover is once assembled therewith, the metal cover may securely push the inner cover downward toward the bottom of the frame. 
         [0006]    The inner cover may further provide a front skirt put between the optical receptacle and the frame. The ceiling makes an obtuse angle with respect to the front skirt when only the front skirt is set between the optical receptacle and the frame and the ceiling is not set between the arms. Thus, when the inner cover is fully assembled with the frame, the front skirt may securely come in contact with the optical receptacle with leaving substantially no gaps therebetween. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    The foregoing and other purposes, aspects and advantages will be better understood from the following detailed description of a preferred embodiment of the invention with reference to the drawings, in which: 
           [0008]      FIG. 1  is a perspective view of an optical transceiver according to an embodiment of the present invention; 
           [0009]      FIG. 2  is an exploded view of the optical transceiver illustrated in  FIG. 1 ; 
           [0010]      FIG. 3  is a perspective view of a frame and an optical receptacle implemented within the optical transceiver shown in  FIG. 1 ; 
           [0011]      FIG. 4  is a cross section taken along the line IV-IV appeared in  FIG. 3 ; 
           [0012]      FIG. 5  is a perspective drawing of an inner cover viewed from the front top; 
           [0013]      FIG. 6  is a perspective drawing of the inner cover viewed from front bottom; 
           [0014]      FIG. 7  is a front view of the inner cover; 
           [0015]      FIG. 8A  shows a state when the inner cover is set between the optical receptacle and the frame but the arms thereof are not assembled with the frame, and  FIG. 8B  shows ,a state when the arms are hooked with the bulge of the side walls of the frame; 
           [0016]      FIG. 9  is a cross section taken along the ling IX-IX in  FIG. 8 ; 
           [0017]      FIG. 10  shows a metal cover according to a modified embodiment of the invention; 
           [0018]      FIG. 11  is a side view of the modified metal cover shown in  FIG. 10 ; and 
           [0019]      FIG. 12  is a perspective drawing of a modified optical receptacle to be assembled with the modified metal cover shown in  FIG. 10 . 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0020]    Next, some preferred embodiments according to the present invention will be described as referring to accompanying drawings. In the description of the drawings, the same numerals or the symbols will refer to the same elements without overlapping explanations. 
         [0021]      FIG. 1  is a perspective view of the optical transceiver according to one embodiment of the present invention; and  FIG. 2  is an exploded view thereof. The optical transceiver  10  illustrated in  FIGS. 1 and 2  has an arrangement following, what is called as the XFP transceiver whose specifications are determined by the multi source agreement. The character “X” means ten (10) in Roman numerals and the operational speed of the XFP transceiver reaches 10 Gbps in the standard. The optical transceiver  10  is implemented within the host system. Specifically, a rear part behind the optical receptacle is set within the cage of the host system as the electrical plug  24  provided in the rear end is mated with the electrical connector provided in the deep end of the cage; while, the optical receptacle in the front end thereof exposes from the port provided in the face plate of the host system to be mated with the external optical connector. 
         [0022]    The optical transceiver  10  further provides a transmitter optical subassembly (hereafter denoted as TOSA)  12 , a receiver optical subassembly (hereafter denoted as ROSA)  14 , the optical receptacle  16 , the frame  18 , an inner cover  20 , a printed circuit board (hereafter denoted as PCB)  24 , and a metal cover  22 . The description below assumes the direction of the frame  18  with respect to the optical receptacle  16  as the rear, while, the direction opposite thereto as the front. Moreover, the upper side is assumed to be a direction of the cover  22  with respect to the frame  18 , while the lower side is opposite thereto. 
         [0023]    The TOSA  12  may emit signal light by receiving an electrical signal from the circuit on the PCB  24 . The TOSA  12  may include a semiconductor laser diode (hereafter denoted as LD), a package that encloses the LD, and a cylindrical sleeve  12   a.  The sleeve  12   a  may receive the optical fiber secured in the external optical connector to couple the LD optically with the optical fiber. The sleeve  12   a  provides two flanges and a neck between flanges. 
         [0024]    The ROSA  14  may convert an optical signal provided from the optical fiber in the external optical connector into an electrical signal and transmits this electrical signal to the circuit on the PCB  24 . The ROSA  14  may include a photodiode (hereafter denoted as PD), a package to enclose the PD, and a cylindrical sleeve  14   a.  The sleeve  14   a  may receive the optical fiber secured in the external optical connector to couple the PD optically with the optical fiber. The sleeve  14   a  provides a flange  14   b  and a neck  14   c  behind the flange  14   b.  The neck  14   c  has a diameter smaller than that of the flange  14   b.    
         [0025]    The TOSA  12  and the ROSA  14  are mounted on the frame  18 .  FIG. 3  is a perspective view showing the frame  18  and the optical receptacle  16 . The optical transceiver  10 , as shown in  FIG. 3 , distinguishes the optical receptacle  16  from the frame  18 . That is, the optical receptacle  16  and the frame  18  are formed independently. However, two members,  16  and  18 , may be integrally formed. 
         [0026]    The optical receptacle  16  is a member to couple the TOSA  12  and the ROSA  14  optically with the external optical fiber. That is, the optical receptacle  16 , which may be coated in surfaces thereof with electrically conductive material, for instance, the optical receptacle  16  may be made of metal die-casting, or resin coated with meal film. The optical receptacle  16  provides two spaces that receive an end of the TOSA sleeve  12   a  and an end of the ROSA sleeve  14   a.  The external optical connected is inserted into the space from the front side and may couple optically with the TOSA sleeve  12   a  and the ROSA sleeve  14   a.    
         [0027]    The optical receptacle  16  provides a rear wall  16   a  where two openings are formed toward two spaces of the optical receptacle  16 . The end of the TOSA sleeve  12   a  and the end of the ROSA sleeve  16   a  are protruded within the spaces through these openings. The frame  18  is set in the rear of the optical receptacle  16 . The frame  18 , which is made of metal, provides an area  18   a  to mount the OSAs,  12  and  14 , and another area  18   b  in the rear of the former area  18   a  to mount the PCB  24 . The frame  18  provides two side walls  18   c  and a bottom  18   d.  The side wall  18   c,  which faces to each other, puts the bottom  18   d  therebetween. 
         [0028]    The frame  18   a  provides a front wall  18   e  in a front side of the area  18   a  to mount the OSAs. The front wall  18   e  has two saddles that mount the neck in the TOSA sleeve  12   a  and that of the ROSA sleeve  14   a.  Two flanges of the TOSA sleeve  12   a  put this saddle therebetween, while the flange  14   b  of the ROSA sleeve  14   a  is set between the front wall  18   e  of the frame  18  and the rear wall  16   a  of the optical receptacle  16 . Thus, the position of the TOSA  12  and that of the ROSA  14  with respect to the optical receptacle  16  may be automatically determined. When the two members,  16  and  18 , are integrally formed, the flange of the TOSA  12  and that of the ROSA  14  abut against the rear wall  16   a  of the receptacle to determine the positions of the OSAs automatically. 
         [0029]    The area  18   a  to mount OSAs is lowered from the area  18   b  for mounting the PCB  24 . That is, the former area  18   a  forms a hollow. The TOSA  12  has a rectangular package  12   e,  as shown in  FIG. 1 , to configure, what is called as the butterfly module. The bottom of the package  12   e  comes thermally in contact with the bottom of the area  18   a  through, for instance, a thermal sheet to secure a heat-dissipating path from the package  12   e  to the frame  18 . The side wall  18   c  rises at the each side of the area  18   a.  As described later, a top of the side wall  18   c  forms a bulge which is coupled with the inner cover  20 . The outer side of the side wall  18   c  provides a hollow  18   f  extending longitudinally that may guide the optical transceiver  10  at the insertion into the cage of the host system. 
         [0030]    The other area  18   b  to mount the PCB  24  forms a terrace. Electrical components mounted on the PCB  24  may come in thermally contact to the bottom  18   d  of the area  18   b.  The components may be in contact with the bottom  18   d  through, for instance, a thermal sheet to secure the heat dissipating path from the circuit to the frame  18 . The area  18   b  may further provide projection  18   h  extending upward, which may set the PCB  24  in the position on the frame  18 . The projection may receive stress applied to the PCB  24  when the transceiver  10  is mated with the electrical connector in the host system. 
         [0031]      FIG. 4  is a cross section taken along the ling IV-IV appeared in  FIG. 3 . The bottom  18   d  in the area  18   a  for mounting the OSAs is lowered compared to the bottom  18   d  in the area  18   b  for the PCB  24 . The optical axis of the TOSA  12  and that of the ROSA  14  may be aligned with the optical axis of the external optical connector by hollowing the bottom of the area  18   a.  Moreover, the package  12   e  of the TOSA  12 , which installs a heat-generating device such as thermo-electric controller (TEC) , may be come in thermally contact to the bottom  18   d  through the thermal sheet. 
         [0032]      FIGS. 5 and 6  are perspective views of the inner cover  20 , where  FIG. 5  vies the inner cover  20  from the front, while,  FIG. 6  views the member from the rear.  FIG. 7  is a front view of the inner cover  20 , while,  FIGS. 8A and 8B  are views where the inner cover  20  is going to be assembled with the frame  18  ( FIG. 8A ), and the member  20  is assembled with the frame  18 . 
         [0033]    The inner cover  20  is assembled with the frame  18  so as to cover the area  18   a  for the OSAs. The member  20  may be formed by a metal plate only by cutting and bending without welding or soldering, which makes the member  20  inexpensive. As shown in  FIGS. 5 to 7 , the inner cover  20  comprises a ceiling  20   a,  a pair of arms  20   b,  a pair of sides  20   c,  and a front skirt  20   d.  The ceiling  20   a  is flat. The side  20   c  may be formed by bending the side end of the ceiling  20   a  downward. The arm  20   b  extends rearward from the rear end of the ceiling  20   a.  The embodiment of the member  20  extends the arm  20   b  from the rear end of the side  20   c.  The front skirt  20   d  may be formed by bending the front end of the ceiling  20   a  downward. 
         [0034]    The cross section of the arm  20   b  is a U-shape but the direction thereof is upside down. Specifically, the arm  20   b  provides two clips,  20   g  and  20   h,  facing to the others. When the inner cover  20  is assembled with the frame  18 , these two clips,  20   g  and  20   h,  put the side wall  18   c  of the frame  18  therebetween. The side  20   c  has a shape tracing the outer clip  20   h  of the arm  20   b  and is formed by bending the ceiling  20   a  downward. The side  20   c  is further bent inward in a tip thereof to form a hook  20   e.  When the inner cover  20  is assembled with the frame  18 , the hook  20   e  may be latched with the bulge  18   i  in the top of the side wall  18   c  of the frame  18 . 
         [0035]    The front skirt  20   d  provides two arched cut  20   f  with a semicircular shape. The front skirt  20   d  is set into a gap between the front wall  18   e  of the frame and the rear wall  16   e  of the optical receptacle  16 . The optical transceiver  10  of the present embodiment provides the frame  18  with the saddles in the front wall  18   e  thereof. The saddle combined with the arched cut  20   f  of the inner cover  20  may form apertures through which the TOSA sleeve  12   a  and the ROSA sleeve  14   a  pass. The arched cur  20   f  has a diameter slightly greater than a diameter of the flange of the TOSA sleeve  12   a  and that of the ROSA sleeve  14   a;  accordingly, the front skirt  20   d  of the inner cover  20  may be free from the flange of the TOSA sleeve  12   a,  that of the ROSA sleeve  14   a,  and the saddle of the front wall  16   e.  Thus, the optical axis of the TOSA sleeve  12   a  and that of the ROSA sleeve  14   a  may be not misaligned with the optical axes of the receptacle  16 . 
         [0036]    As shown in  FIG. 8A , the front skirt  20   d  makes an obtuse angle to the ceiling  20   a  when the inner cover  20  is not fully assembled with the frame  18 .  FIG. 8A  illustrates a status when only the front skirt  20   d  is put between the rear wall  16   a  of the optical receptacle  16  and the front wall  18   e  of the frame  18 ; and the ceiling  20   a  and two arms  20   b  are free from the frame  18 . The angle between the front skirt  20   d  and the ceiling  20   a  may be, for instance, 90 to 120 degrees. 
         [0037]    As shown in  FIG. 8B , mating the arm  20   b  with the side wall  18   c  in the top thereof and latching the hook  20   e  with the bulge  18   i , the angle between the front skirt  20   d  and the ceiling  20   a  is reduced close to a right angle. Concurrently, the front skirt  20   d  pushes the rear wall  16   a  frontward, which makes the front skirt  20   d  securely in contact to the rear wall  16   a  without forming a gap therebetween. 
         [0038]      FIG. 9  is a cross section taken along the line IX-IX appeared in  FIG. 8B . The arms  20   b  have a span therebetween slightly larger than a span between the side walls  18   c  when the inner cover  20  is not assembled with the frame  18 . Assembling the inner cover  20  with he frame  18  by latching the hook  20   e  with the bulge  18   i , the ceiling  20   a  rises in a center thereof upward as shown in  FIG. 9  and the ceiling  20   a  makes a convex surface. Then, the metal cover  22  is set in the frame  18  so as to enclose the inner cover  20 . 
         [0039]    The cover  22  may be also formed by a metal sheet only by cutting and bending without welding or soldering. As illustrated in  FIG. 2 , the cover  22  includes a top  22   a,  a pair of girders  22   b , and a pair of sides  22   d.  The top  22   a  covers two areas,  18   a  and  18   b , and the inner cover  20 . The side  22   d  provides an opening  22   c  engaged with a projection  18   k  provided in the side wall  18   c  of the frame  18 , which may assembles the cover  22  with the frame  18 . The girder  22   b  is arranged outside of the side  20   c  and the outer clip  20   h  of the arm  20   b  so as to put the side wall  18   c  therebetween. 
         [0040]    Assembling the cover  22  with the frame  18 , the top  22   a  of the cover  22  pushes the ceiling  20   a  of the inner cover  20  downward, which may come the cover  22  securely in contact with the inner cover  20  without forming a gap therebetween. Moreover, the inner cover  20  pushed downward by the cover  22  causes a transverse expansion of the member  20 . However, the girders  22   b  in each side of the cover  22  may effectively prevent this transverse expansion of the inner cover  20 . 
         [0041]    Although the present invention has been fully described by the preferred embodiment thereof as referring to the accompanying drawings, it is to be understood that various changes and modifications may be apparent to those skilled in the art.  FIG. 10  is a perspective view of a modified cover  22 A,  FIG. 11  is a side view thereof, and  FIG. 12  is a perspective view of an optical receptacle  16 A assembled with the frame  18 . 
         [0042]    As illustrated in  FIGS. 10 and 11 , the modified cover  22 A includes a front portion  22   f  and a rear portion  22   r.  The former portion  22   f  is assembled with the optical receptacle  16 A, while, the latter portion  22   r  is assembled with the frame  18 . The former cover  22  provides a flat top  22   a,  while, the modified cover  22 A provides two portions,  22   f  and  22   r,  which make a substantial obtuse angle therebetween. That is, the top  22   a  in the front portion  22   f  makes an angle of, for instance 173±2° with respect to the top  22   a  in the rear portion  22   r.  The top  22   a  in the rear portion  22   r  is tilted upward by 7±2° with respect to the top  22   a  of the front portion  22   f . Additionally, the top  22   a  of the front portion  22   f  in the front edge thereof protrudes two tabs  22   p.    
         [0043]    As shown in  FIG. 12 , the modified optical receptacle  16 A also includes a front portion  16   f  and a rear portion  16   r,  and a step  16   s  between two portions,  16   f  and  16   r.  The step  16   s  provides two openings  16   h  directing the front, into which the tabs  22   p  of the cover  22 A are inserted. The cover  22 A may be assembled with the optical receptacle  16 A such that two tabs  16   p  are first inserted into the openings  16   h  and then the opening  22   c  in the front portion  22   f  of the cover  22 A is going to be mated with the projection  16   p  provided in the side of the optical receptacle  16 A. In this state, the rear portion  22   r  of the cover  22 A rises from the frame  18 . 
         [0044]    Mating the opening  22   c  in the rear portion  22   r  with the projection  18   k  of the frame  18 , the cover  22 A may be securely assembled with the frame  18  and the optical receptacle  16   a.  In these arrangements of the cover  22 A, the optical receptacle  16 A and the frame  18 ; the cover  22 A may further push the inner cover  20  downward compared to the arrangement of the cover  22  in the aforementioned embodiment. Because the tabs  22   p  of the cover  22 A are inserted into the openings  16   h,  substantially no gaps may be formed between the ceiling  20   a  and the cover  22 A even when the inner cover  20  lifts up the cover  22 A. Thus, the optical transceiver according to the present embodiment may effectively enhance the EMI shielding. The embodiment shown in  FIG. 12  provides two tabs  22   p  and two openings  16   h.  However, the number of tabs  22   p  and that of the holes  16   h  may be optional.