Abstract:
In an optical module, a package includes an array of first optical elements and at least one first positioning member. A microlens array plate including microlenses is fixed to the package, so that each of the microlenses corresponds to one of the first optical elements. An optical array connector mounts second optical elements thereon. The optical array connector has a light path bending portion for bending light paths of the second optical elements and at least one second positioning member. The optical array connector abuts against the package by aligning the second positioning member to the first positioning member so that each of the first optical elements corresponds to one of the second optical elements, A clamping member clamps the optical, array connector to the package.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to an optical module formed by a package for receiving and emitting light and an optical connector, and more particularly, to the improvement of a coupling structure between the package and the optical connector and its manufacturing method. 
   2. Description of the Related Art 
   Optical interconnection of the LSI packages with each other by optical fibers or optical waveguides is attractive in order to enhance thee operation speed in a computer system where large scale integrated circuit (LSI) packages such as a central processing unit (CPU) and memories are mounted on a board. 
   Connecting the LSI packages with each other by using optical interconnection modules is one of possible way to establish inter-LSI package optical interconnection. In this configuration, however, the redundant portions of the optical fibers would need to be processed. Because the most of optical interconnection module have pig-tailed optical fibers of normalized length and these fibers are not detachable from the module. To avoid the optical fiber occupation on the board, it is preferable that the optical fibers are removable from the optical module. By this, optical modules are connected each other by optical fibers of preferable lengths. 
   Optical modules without pig-tailed optical fibers have been suggested. That is, optical fibers are removable from LSI packages, In this case, if the optical fibers are moved in the horizontal direction to couple with the LSI packages, dead space due to the horizontal motion of the optical fibers may be created on a board, so that the mounting density of LSI packages on the board is decreased. Therefore, it is preferable that the optical fibers be moved in the vertical direction to couple with the LSI packages. 
   In a first prior art optical module (see: JP-A-4-308804), an array of optical fibers adhered to a microlens array is moved down to couple with an LSI package, so that the above-mentioned dead space on a board is decreased to increase the mounting density of LSI packages on the board. This will be explained later in details 
   In the above-described first prior art optical module, however, if the alignment of the optical fibers to the LSI package fluctuates, the coupling efficiency therebetween deteriorates. 
   In a second prior art optical module (see: JP-A-10-115732), an optical fiber with a mirror and a half mirror is moved down to couple with a package. This also will be explained later in detail. 
   In the above-described second prior art optical module, however, since the mirror and the half mirror are protruded from the bottom surface of the optical fiber, the coupling between the optical fiber and the package is carried out by a transparent adhesive layer, so that it is impossible to remove the optical fiber from the package. Thus, the optical fiber is not removable. If the optical fiber is forcibly removed from the package and is again fixed to the package or another package, the coupling loss fluctuates. 
   SUMMARY OF THE INVENTION 
   It is an object of the present invention to provide an optical module capable of improving the coupling efficiency and suppressing the fluctuation of the coupling loss. 
   Another object is to provide a method for manufacturing such an optical module. 
   According to the present invention, in an optical module, a package includes an array of first optical elements and at least one first positioning member. A microlens array plate including microlenses is fixed to the package, so that each of the microlenses corresponds to one of the first optical elements. An optical array connector mounts second optical elements thereon. The optical array connector has a light path bending portion for bending light paths of the second optical elements and at least one second positioning member. The optical array connector abuts against the package by aligning the second positioning member to the first positioning member so that each of the first optical elements corresponds to one of the second optical elements. A clamping member clamps the optical array connector to the package. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will be more clearly understood from the description set forth below, as compared with the prior art, with reference to the accompanying drawings, wherein: 
       FIG. 1  is an exploded, perspective view illustrating a first prior art optical module; 
       FIG. 2  is a view of an assembled state of the optical module of  FIG. 1 ; 
       FIG. 3  is a diagram illustrating a second prior art optical module; 
       FIG. 4  is an exploded, perspective view illustrating a first embodiment of the optical module according to the present invention; 
       FIG. 5  is a cross-sectional view of the fiber array connector of  FIG. 4 ; 
       FIGS. 6A ,  6 B,  6 C and  6 D are cross-sectional views for explaining an assembling operation of the optical nodule of  FIG. 4 ; 
       FIG. 7  is an exploded, perspective view illustrating a first modification of the optical module of  FIG. 4 ; 
       FIG. 8  is an exploded, perspective view illustrating a second modification of the optical nodule of  FIG. 4 ; 
       FIG. 9  is an exploded, perspective view illustrating a second embodiment of the optical module according to the present invention; and 
       FIG. 10  is an exploded, perspective view illustrating a third embodiment of the optical module according to the present invention., 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Before the description of the preferred embodiments, prior art optical modules will be explained with reference to  FIGS. 1 ,  2  and  3 . 
   In  FIG. 1 , which illustrates a first prior art optical module (see: JP-A-4-308804), an LSI package  101  includes LSI chips (not shown) and optical elements  101   a  such as surface-emitting laser diodes and surface-receiving PIN photodiodes electrically connected to the LSI chips. Also, an array of optical fibers  102  are provided to correspond to the optical elements  101   a . In this case, each of the optical fibers  102  is constructed by a core layer  102   a  and a clad layer  102   b  surrounding the core layer  102   a.  The facets of the optical fibers  102  are oblique, i.e., at 45° to the optical axes thereof, and a plane portion  102   c  is formed at the clad layer  102   b  of each of the optical fibers  102 . Further, a microlens array  103  is provided. 
   After a surface of the microlens array  103  is adhered to the plane portions  102   c  of the optical fibers  102 , the optical fibers  102  are moved down so that the other surface of the microlens array  103  is adhered to the LSI package  101 . 
   Thus, as illustrated in  FIG. 2 , light emitted from of the optical elements  101   a  is transmitted through the microlens array  103  and is reflected by the facet of one of the optical fibers  102  to pass through the core layer  102   a  thereof. On the other hand, light emitted from the core layer  102   a  of one of the optical fibers  102  is reflected by the facet of one of the optical fibers  102  and is transmitted through the microlens array  103  to reach a respective one of the optical elements  101   a.    
   If the array of the optical fibers  102  adhered to the microlens array  103  are removable from the LSI package  101 , the alignment of the optical fibers  102  to the LSI package  101 must be accurate. For example, if the diameter of the optical element  110   a  is less than 30 μm, the error of the alignment of the optical fibers  102  to the LSI package  101  must be less than 5 μm. Therefore, if the alignment of the optical fibers  102  to the LSI package  101  fluctuates as indicated by dotted lines in  FIG. 2 , the coupling efficiency thereof deteriorates. 
   In  FIG. 3 , which illustrates a second prior art optical module (see: JP-A-10-115732), a silicon substrate  202  is adhered to a package  201 , and a surface-emitting laser diode  203  and a surface-receiving PIN photodiode  204  are adhered to the silicon substrate  202 . Also, a ceramic plate  205  for fixing microlenses  206  and  207  is placed on the package  201 . 
   Also, an optical fiber  208  supported by a precision capillary  209  is buried in a groove of a fiber burying substrate  210  which has an oblique end face for mounting a mirror  211  and a groove for mounting a half mirror  212 . 
   The fiber burying substrate  210  having the optical fiber  208 , the mirror  211  and the half mirror  212  is moved down, so that the fiber burying substrate  210  is fixed by a transparent adhesive layer  213  to the ceramic plate  205 . 
   Thus, light emitted from the laser diode  203  is transmitted through the microlens  206  and is reflected by the mirror  211  to pass through the half mirror  212 . On the other hand, light from the optical fiber  208  is reflected by the half mirror  212  and is transmitted through the microlens  207  to reach the PIN photodiode  204 . 
   In the optical module of  FIG. 3 , however, since the mirror  211  and the half mirror  212  are protruded from the bottom surface of the optical fiber  208  buried in the fiber burying substrate  210 , use is made of the transparent adhesive layer  213  in order to fix the optical fiber  208  to the package  201 , i.e., the ceramic plate  205  with the microlenses  206  and  207 , which would make it impossible for the optical fiber  208  to remove from the package  201 . Thus, the optical fiber  208  is not removable. If the optical fiber  208  is forcibly removed from the package  201  and the optical fiber  208  is again fixed to the package  201  or another package, the coupling loss fluctuates. 
   In  FIG. 4 , which illustrates a first embodiment of the optical module according to the present invention, an LSI package  1  includes LSI chips (not shown), and surface-emitting laser diodes  11  and surface-receiving PIN photodiodes  12  electrically connected to the LSI chips. For example, the pitch of the laser diodes  11  and the pitch of the PIN photodiodes  12  are 250 μm. The laser diodes  11  and the PIN photodiodes  12  are exposed by a rectangular opening  13  on the upper side of the LSI package  1 . Also, guide recesses  14 - 1  and  14 - 2  are perforated on the upper side of the LSI package  1 . Further, recesses  15 - 1  and  15 - 2  are perforated on the sides of the LSI package  1 . 
   A microlens array plate  2  includes microlenses  21  corresponding to the laser diodes  12  and the PIN photodiodes  13 . In this case, the microlens array plate  2  can be fitted into the rectangular opening  13  of the LSI package  1 , and the pitch of the microlenses  21  is 250 μm, for example. 
   An optical array connector, i.e., a fiber array connector  3  has V-shaped grooves  31  on its bottom side for receiving optical fibers  4 . Also, as illustrated in  FIG. 5 , a vertical stopper face  32  for stopping the optical fibers  4  and an oblique face  33  having an approximate angle of 45°, and a vertical stopper face  34  for stopping a glass plate  5  are provided in the fiber array connector  3 . Note that a mirror  33   a  made of an Au layer is deposited by an evaporation process on the oblique face  33 . Also, guide recesses  35 - 1  and  35 - 2  corresponding to the guide recesses  14 - 1  and  14 - 2  of the LSI package  1  are perforated on the bottom side of the fiber array connector  3 . 
   Guide pins  6 - 1  and  6 - 2  are used for aligning the fiber array connector  3  to the LSI package  1 . 
   A clamping member  7  is used for clamping (fixing) the fiber array connector  3  to the LSI package  1 . The clamping member  7  is made of adiabatic material and has two nails  71 - 1  and  71 - 2  corresponding to the recesses  15 - 1  and  15 - 2  of the LSI package  1 . 
   The assembling operation of the optical module of  FIG. 4  is explained below. 
   First, as indicated by {circle around (1)}, the microlens array plate  2  is fitted into the opening  13  of the LSI package  1 , so that the optical axes of the microlenses  21  are in alignment with these of the laser diodes  11  and the PIN diodes  12 , as illustrated in FIG.  6 A. 
   Next, as indicated by {circle around (2)}, the optical fibers  4  are fitted into the V-shaped grooves  31  of the fiber array connector  3 , so that the facet of the optical fibers  4  abuts against the vertical stopper face  32  of the fiber array connector  3 , as illustrated in FIG.  6 B. In  FIG. 6B , note that each of the optical fibers  4  is constructed by a core layer  41  and a clad layer  42 . 
   Next, as indicated-by {circle around (3)}, the glass plate  5  is adhered to the optical fibers  4  after a transparent resin layer  8  is fitted into a spacing between the optical fibers  4  and the mirror  33   a , as illustrated in FIG.  6 C. In this case, the glass plate  5  abuts against the vertical stopper face  34  of the fiber array connector  3 . As a result, the optical fibers  4  are securely fitted into the V-shaped grooves  31  of the fiber array connector  3 . Note that the transparent resin layer  8  is made of ultraviolet thermosetting adhesives. Therefore, when such adhesives are coated on the upper and lower faces of the optical fibers  4 , the glass plate  5  is surely adhered to the optical fibers  4 . Also, the transparent resin layer  8  serves as a refractive index matching element between the LSI package  1  and the optical fibers  4 , to suppress the spread of light reflected from the mirror  33   a , light from the optical fibers  4  and light to the optical fibers  4 . 
   Next, as indicated by {circle around (4)}, the fiber array connector  3  with the optical fibers  4  and the glass plate  5  is moved down while the guide pin  6 - 1  is fitted into the guide recesses  14 - 1  and  35 - 1  and the guide pin  6 - 2  is fitted into the guide recesses  14 - 2  and  35 - 2 . Thus, the optical fibers  4  are surely in alignment with the laser diodes  11  and the PIN photodiodes  12 . 
   Finally, as indicated by {circle around (5)}, the clamping member  7  clamps the fiber array connector  3  to the LSI package  1  by inserting the nails  71 - 1  and  71 - 2  into the recesses  15 - 1  and  15 - 2  of the LSI package  1 . As a result, the fiber array connector  3  couples with the LSI package  1 , as illustrated in FIG.  6 D. 
   In  FIG. 6D , light emitted from the laser diodes  11  is transmitted through the microlenses  21  and the glass substrate  5 , and is reflected by the mirror  33   a  to reach the optical fibers  4 . On the other hand, light emitted from the optical fibers  4  is reflected by the mirror  33   a , and is transmitted through the glass plate  5  and the microlenses  21  to reach the PIN diodes  12 . 
   The disassembling operation of the assembled optical module of  FIG. 5  is carried out just by removing the clamping member  7  therefrom. As a result, the fiber array connector  3  with the optical fibers  4  and the glass plate  5  can be easily separated from the LSI package  1 . 
   Thus, in the,first embodiment, since the optical fibers  4  are securely adhered to the LSI package  1 , the coupling efficiency therebetween can be improved. Also, since the fiber array connector  3  with the optical fibers  4  is completely removable from the LSI package  1 , the fluctuation of coupling loss can be suppressed. 
   In  FIG. 7 , which illustrates a first modification of the optical module of  FIG. 4 , balls  14 ′- 1  and  14 ′- 2  adhered to the upper face of the LSI package  1  are provided instead of the guide recesses  14 - 1  and  14 - 2  of  FIG. 4 , and recesses  35 ′- 1  and  35 ′- 2  are provided instead of the guide recesses  35 - 1  and  35 - 2  of FIG.  4 . In this case, the guide pins  6 - 1  and  6 - 2  of  FIG. 4  are not provided. As a result, as indicated by {circle around (4)}, the fiber array connector  3  with the optical fibers  4  and the glass plate  5  is moved down while the balls  14 - 1  and  14 - 2  are fitted into the recesses  35 ′- 1  and  35 ′- 2 . Thus, the optical fibers  4  are also surely in alignment with the laser diodes  11  and the PIN photodiodes  12 . 
   In the modification as illustrated in  FIG. 7 , the balls  14 ′- 1  and  14 ′- 2  can be provided on the lower face of the fiber array connector  3  and the recesses  35 ′- 1  and  35 ′- 2  can be provided on the upper face of the LSI package  1 . 
   In  FIG. 7 , since the guide pins  6 - 1  and  6 - 2  of  FIG. 4  are not provided, the optical module of  FIG. 7  can be thinner as compared with that of FIG.  4 . 
   In  FIG. 8 , which illustrates a second modification of the optical module of  FIG. 4 , pyramid-shaped protrusions  14 ″- 1  and  14 ″- 2  adhered to the upper face of the LSI package  1  are provided instead of the guide holes  14 - 1  and  14 - 2  of  FIG. 4 , and pyramid-shaped recesses  35 ″- 1  and  35 ″- 2  are provided instead of the guide recesses  35 - 1  and  35 - 2  of FIG.  4 . In this case, the guide pins  6 - 1  and  6 - 2  of  FIG. 4  are not provided. As a result, as indicated by {circle around (4)}, the fiber array connector  3  with the optical fibers  4  and the glass plate  5  is moved down while the protrusions  14 ″- 1  and  14 ″- 2  are fitted into the recesses  35 ″- 1  and  35 ″- 2 . Thus, the optical fibers  4  are also surely in alignment with the laser diodes  11  and the PIN photodiodes  12 . 
   In the modification as illustrated in  FIG. 8 , the protrusions  14 ″- 1  and  14 ″- 2  can be provided on the lower face of the fiber array connector  3  and the recesses  35 ″- 1  and  35 ″- 2  can be provided on the upper face of-the LSI package  1 . However, if the fiber array connector  3  is made of monocrystalline silicon, the recesses  35 ″- 1  and  35 ″- 2  can be easily formed by an anisotropy etching process. 
   Even in  FIG. 8 , since the guide pins  6 - 1  and  6 - 1  of  FIG. 4  are not provided, the optical module of  FIG. 8  can be thinner as compared with that of FIG.  4 . 
   In  FIG. 9 , which illustrates a second embodiment of the optical nodule according to the present invention, an optical waveguide, array  4 ′ is provided instead of the optical fibers  4  of  FIG. 4 , and a recess  31 ′ is provided instead of the V-shaped grooves  31  of  FIG. 4  in an optical array connector  3 ′. Assembling and disassembling operation of the optical module of  FIG. 9  can be carried out in a similar way as in the optical module of FIG.  4 . Also, the modifications of  FIGS. 7 and 8  can be applied to the optical module of FIG.  9 . 
   In  FIG. 10 , which illustrates a third embodiment of the optical module according to the present invention, a capillary  31 ″ is provided instead of the V-shaped grooves  31  of  FIG. 4 , Assembling and disassembling operation of the optical module of  FIG. 10  can be carried out in a similar way as in the optical module of FIG.  4 . Also, the modifications of  FIGS. 7 and 8  can be applied to the optical module of FIG.  10 . 
   In the above-described embodiments, the package  1  is manufactured by a transfer molding process using resin, so that the guide holes  14 - 1  and  14 - 2  (the balls  14 ′- 1  and  14 ′- 2  the protrusions  14 ″- 1  and  14 ″- 2 ) and the recesses  15 - 1  and  15 - 2  can be simultaneously formed. On the other hand, the fiber array connector  3  (optical array connector  3 ′) is manufactured by a transfer molding processing resin, so that the V-shaped grooves  31 , vertical stopper face  32 , the oblique face  33  and the vertical stopper face  33 , the guide recesses  35 - 1  and  35 - 2  (the recesses  35 ′- 1 ,  35 ′- 2 ,  35 ″- 1  and  35 ″- 2 ) can be simultaneously formed, 
   As explained hereinabove, according to the present invention, since the alignment of an optical array connector (fiber array connector) to a package does not fluctuate, the coupling efficiency can be improved. Also, since the optical array connector is completely removable from the package, the fluctuation of the coupling loss can be suppressed.