Abstract:
An optical module includes: an optical plug that supports one end of an optical fiber; a receptacle unit having an optical element and a mounting surface to be abutted against the optical plug for optically coupling the optical plug and the optical element; and a holder having a leaf spring that forces the optical plug to the mounting surface of the receptacle unit, a window section for passing the optical fiber, and a fiber support section disposed at a position near the window section for affixing the optical fiber thereto, wherein the holder is engaged with the receptacle unit to connect the receptacle unit and the optical plug in one piece.

Description:
The entire disclosure of Japanese Patent Application No. 2006-018724, filed Jan. 27, 2006 is expressly incorporated by reference herein. 
   BACKGROUND 
   1. Technical Field 
   The present invention relates to optical modules that are used for optical communications. 
   2. Related Art 
   As a typical example of an optical module that is used for optical communications optical module, an optical module described in Japanese laid-open patent application JP-A-2003-207694 (patent document 1) is known. The optical module described in the above document uses a structure in which an optical fiber connector with an array of optical fibers being bonded thereto is pushed toward a package by a clamp thereby affixing the optical fiber connector to the package. 
   However, in the optical module described above, the optical fiber connector, the clamp and the package are composed as separate and independent members, such that the work in assembling these members is complex. Also, when an external force (such as, a force to pull up) is applied to the optical fibers, positions between the optical fiber connector, the clamp and the package would likely be shifted from one another, which may lower the optical coupling efficiency. 
   SUMMARY 
   In accordance with an advantage of some aspects of the present invention, it is possible to provide an optical module that can be readily assembled, and suppress a reduction in the optical coupling efficiency due to positional shifts among components of the optical module. 
   An optical module in accordance with an embodiment of the invention includes: an optical plug that supports one end of an optical fiber; a receptacle unit having an optical element and a mounting surface to be abutted against the optical plug for optically coupling the optical plug and the optical element; and a holder having a leaf spring that forces the optical plug to the mounting surface of the receptacle unit, a window section for passing the optical fiber, and a fiber support section disposed at a position near the window section for affixing the optical fiber thereto, wherein the holder is engaged with the receptacle unit to connect the receptacle unit and the optical plug in one piece. 
   By the structure described above, as the optical fiber is affixed by the fiber support member, the optical plug and the holder secure some degree of freedom in mutual positioning, and can be handled together. Accordingly, the work in assembling the optical plug and the receptacle unit by the holder becomes easier. Also, as the optical fiber is affixed to the holder, the optical plug that supports one end of the optical fiber would not be substantially shifted. Therefore, a reduction in the optical coupling efficiency due to positional shift between the optical plug and the receptacle unit can be suppressed. 
   Preferably, the fiber support member may include a plate section and adhesive that bonds the plate section and the optical fiber. 
   By this, the optical fiber can be more securely affixed to the holder. 
   Preferably, the plate section of the fiber support section may be disposed in contact with a side of the window section. 
   As a result, the optical fiber can be affixed at a position close to the window section. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is an exploded perspective view of the overall structure of an optical module in accordance with an embodiment of the invention. 
       FIG. 2  is an exploded perspective view of the structure of the optical module showing a plug unit and a receptacle unit separated from each other. 
       FIG. 3  is a cross-sectional view of the optical module taken along a direction in which the optical fiber extends. 
   

   DESCRIPTION OF EXEMPLARY EMBODIMENTS 
   Preferred embodiments of the invention are described below with reference to the accompanying drawings. 
     FIG. 1  is an exploded perspective view of the overall structure of an optical module in accordance with an embodiment of the invention.  FIG. 2  is an exploded perspective view of the structure of the optical module showing a plug unit and a receptacle unit separated from each other.  FIG. 3  is a cross-sectional view of the optical module taken along a direction in which the optical fiber extends. The optical module in accordance with the present embodiment shown in  FIGS. 1-3  is an optical module that is disposed on a substrate (circuit substrate) equipped with, for example, an electrical circuit, and is formed from an optical plug  1 , a clamp (holder)  2 , a ceramic package  3 , a resin package  4 , and an optical block  5 . The optical plug  1  and the clamp  2  jointly form a plug unit; and the ceramic package  3 , the resin package  4  and the optical block  5  jointly form a receptacle unit. 
   The optical plug  1  supports one end of the optical fiber  6 . The optical plug  1  may be formed by, for example, resin injection molding. The optical plug  1  has V-letter shaped grooves and a plate member that covers the grooves. One ends of the optical fibers  6  are disposed in the V-letter shaped grooves, and the ends of the optical fibers are pressed by the plate member, thereby supporting the optical fibers  6 . Also, the optical plug  1  has a focusing lens  11  disposed on an optical axis of the optical fiber  6 . In the example shown in the figure, a plurality of focusing lenses  11  are provided at one end side of the optical plug  1  in its longitudinal direction. 
   The clamp  2  is disposed in a manner to surround the entire body of the receptacle unit, thereby join the optical plug  1  and the receptacle unit in one piece. The clamp  2  may be formed, for example, from a metal plate that is punched out and bent by a press machine. The clamp  2  is equipped with generally J-letter shaped hooks  21  on its side surfaces, leaf springs  22 , engagement holes  24 , a fiber support member  25  and a window section  26 . The clamp  2  is engaged with the receptacle unit, thereby joining the receptacle unit and the optical plug  1  together in one piece. 
   The hooks  21  engage with latch sections  44  of the resin package  4 . By this, the receptacle unit and the plug unit are joined together in one piece. 
   The leaf spring  22  may be formed through cutting an upper portion of the clamp  2  in a generally H-letter shape. The leaf springs  22  force end sections of the optical plug  1  in its longitudinal direction toward a mounting surface  42  of the resin package  4 . By this, the optical plug  1  is brought in tight contact with the resin package  4 . 
   A light shield section  23  is disposed at a tip end side of the clamp  2 , in a manner to intersect the optical axis of the optical fiber  6 . The light shield section  23  is a plate portion formed by bending a portion of the clamp  2  as illustrated. The light shield section  23  prevents laser light emitted from the optical plug  1  from leaking outside, when the plug unit is not coupled with the receptacle unit. 
   The engagement holes  24  are provided in a plate portion that is formed by bending a portion of the clamp  2  at its rear end side. Two engagement holes  24  are provided in the present example. The engagement holes  24  function to retain the receptacle unit and the plug unit in one piece by engaging with engaging pins (protruded sections)  41  provided on the resin package  4 , respectively. 
   The fiber support section  25  is formed by bending a portion of the plate portion of the clamp  2  at its rear end side. The fiber support section  25  in the present example is interposed between the two engagement holes  24  generally at the center of the read end side of the clamp  2 . When the optical plug  1  is covered by the clamp  2 , the optical fiber  6  is disposed at the fiber support section  25 . The fiber support section  25  in accordance with the present embodiment includes a plate section  25   a  disposed in contact with one side of the window section  26 , and adhesive  25   b  that bonds the plate section  25   a  and a portion of the optical fiber  6 , as shown in the figure. 
   The window section  26  is formed by cutting a portion of a plate section that is formed by bending a portion of the clamp  2  on its end side. The window section  24  of the present example is interposed between the engagement holes  24 . It is noted that the window section  26  of the present example has one side (at a lower end side) that is open, but this side may be closed. When one side of the window is open, the optical fiber  6  can be more readily disposed in the fiber support section  25 , when the optical plug  1  and the clamp  2  are joined together. 
   The ceramic package  3  stores the optical element  31  (see  FIG. 3 ), and has an electrode  32  that is electrically connected to the optical element  31 . More specifically, the ceramic package  3  is formed with ceramics material, and is equipped with a box shaped member  34  having a recessed section for disposing the optical element  31 , the circuit chip  33  and the like, and a transparent plate (a glass plate)  35  disposed on the upper side of the box shaped member  34  in a manner to cover the aforementioned recessed section. The box shaped member  34  and the transparent plate  35  seal up the optical element  31  and the circuit chip  33 . 
   The optical element  31  is a light emission element (for example, a VCSEL) that outputs optical signals, or a photodetecting element that receives optical signals. The optical element  31  is disposed with its optical axis being generally perpendicular to the transparent plate  35 , and outputs optical signals through the transparent plate  35  or receives optical signals. 
   The circuit chip  33  may be a driver that drives the optical element  31 , when the optical element  31  is a light emission element; and may be an amplifier that amplifies electrical signals outputted from the optical element  31 , when the optical element  31  is a photodetecting element. In the present example, the optical element  31  and the circuit chip  33  are connected by wire bonding. 
   The electrode  32  is formed in a manner that a part thereof is exposed outside, and is connected to the optical element  31  and the circuit chip  33  through wirings that pass through the box shaped member  34 . The electrode  32  shall be described in greater detail below. 
   The resin package  4  functions to support and position the optical plug  1 , and is disposed along the optical axis direction of the optical fiber  6 , juxtaposed with the ceramic package  3 . The resin package  4  is equipped with the engaging pins  41  described above, the guide surfaces  42  and  43 , the latch sections  44  and a plurality of lead electrodes  45 . The resin package  4  can be fabricated by, for example, transfer molding with thermosetting type resin such as epoxy resin. When an epoxy resin material mixed with glass fine particles or fibers is used, the dimensional accuracy can be increased, and precise guide surfaces can be formed. 
   The optical plug  1  is mounted on the guide surface (i.e., the mounting surface)  42 . In the present embodiment, the guide surface  42  is formed to be generally in parallel with the surface of the circuit substrate  100  when the optical module is disposed on the circuit substrate  100 . 
   The guide surface  43  is formed such that the guide surface  43  is disposed generally orthogonal to the guide surface  42 . The guide surface  43  contacts the side surface of the optical module. The optical module is positioned by the guide surface  43 , the guide surface  42 , the leaf spring  22 , and the optical block  5 . 
   The plural lead electrodes  45  are provided with a part thereof enclosed by the resin package, and in a manner to protrude toward the lower surface (second surface)  46  that is to be opposed to the circuit substrate  100  of the resin package  4 . In the present embodiment, four lead electrodes  45  are provided on each of the sides of the resin package  4  along its longitudinal direction. Also, in accordance with the present embodiment, the lead electrodes  45  are not used for securing electrical connection, but instead used for joining and affixing the resin package  4  onto the circuit substrate  100 . It is noted however that the lead electrodes  45  may also be used to secure electrical connection. 
   The optical block  5  has a light reflection surface  51  that is disposed at an intersection between the optical axis of the optical element  31  and the optical axis of the optical fiber  6 , The optical block  5  is disposed on the guide surface  42  of the resin package  4 . Also, the optical block  5  is composed of light transmissive resin, and has a sloped surface by cutting a portion of the resin, wherein the sloped surface functions as a light reflection surface  5 . More concretely, optical signals outputted from the optical element  31  are focused by the focusing lens formed at the lower surface of the optical block  5 , reflected by the light reflection surface  51 , and enter one end of the optical fiber  6 . Also, optical signals outputted from the optical fiber  6  are reflected by the light reflection surface  51 , focused by the focusing lens described above, and reach the optical element  31 . 
   Next, a state in which the optical module is mounted on the circuit substrate  100  is described in detail. 
   The electrode  32  provided at the ceramic package  3  has, as shown in  FIG. 3 , an exposed portion  32   a  provided on the side surface of the ceramic package  3 , and a pad section  32   b  provided on the lower surface of the ceramic package  3 . In the present embodiment, each of the electrodes  32  is provided in a plane orthogonal to an extending direction of the optical fiber  6  mounted on the optical module of the ceramic package  3  (i.e., in a plane in parallel with YZ plane). Also, the electrodes  32  are electrically connected and mechanically affixed to connection pads or the like on the circuit substrate  100  through solder  37 . More specifically, as shown in  FIG. 3 , each of the electrodes  32  is bonded to the circuit substrate  100  in a manner that both of the exposed portion  32   a  and the pad section  32   b  are in contact with the solder  37 . It is noted that either the exposed portion  32   a  or the pad section  32   b  alone may be in contact with the solder. 
   Each of the lead electrodes  45  of the resin package  4  is formed in a generally L-letter shape as shown in  FIG. 1 , and provided along the side surface  47  and the lower surface (second surface)  46  of the resin package  4 . Also, as shown in  FIG. 2  in broken lines, a portion of the lead electrode  45  is included in the resin package  4 . As shown in  FIG. 3 , each of the lead electrodes  45  is mechanically affixed to a connection pad or the like on the circuit substrate  100  through solder  48  at the portion of the lead electrode protruding on the lower surface  46  of the resin package  4 . 
   According to the embodiment described above, as the optical fiber is affixed by the fiber support member, the optical plug and the holder secure some degree of freedom in mutual positioning, and can be handled together. Accordingly, the work in assembling the optical plug and the receptacle unit by the holder becomes easier. Also, as the optical fiber is affixed to the holder, the optical plug that supports one end of the optical fiber would not be substantially shifted. Therefore, a reduction in the optical coupling efficiency due to positional shift between the optical plug and the receptacle unit can be suppressed. 
   It is noted that the invention is not limited to the details of the embodiment described above, and many changes can be made and implemented within the scope of the subject matter of the invention.