Abstract:
In an optical transmission module having a communication module which is freely movable in a case, when a tensile force is generated on an optical cable after connection of an optical transmission module, optical coupling surface and an optical axis center follow each other and thus stable optical transmission can be constantly performed.

Description:
CLAIM OF PRIORITY  
       [0001]     The present application claims priority from Japanese patent application serial no. 2005-358808, filed on Dec. 13, 2005, the content of which is hereby incorporated by reference into this application.  
       BACKGROUND OF THE INVENTION  
       [0002]     The present invention relates to an optical transmission module, and particularly to a receptacle-type optical transmission module having an optical transmitter module or an optical receiver module.  
         [0003]     A receptacle-type optical transmission module is configured such that a coaxial can package or box-type package in which a light emitting element or a light receiving element is stored and sealed and a circuit substrate in which electronic components are implemented (a transmission control circuit of a peripheral circuit of the light emitting element or the light receiving element) are stored in one case. The receptacle-type optical transmission module also has a receptacle-type optical connector integrally formed with the case so as to connect an optical transmission plug to the coaxial can package or box-type package from the outside. The optical transmitter module or optical receiver module of the coaxial can package or box-type package is fixed to the case. Such a receptacle-type optical transmission module is described in Patent References 1 to 3. Here, Patent Reference 1 is the US counterpart of Patent References 2 and 3.  
         [0004]     Patent References 4 and 5 describe an optical semiconductor module having a movable ferrule. Further, Patent References 6 to 9 describe an optical connector which is characterized in the configuration of a hook.  
         [0005]     Incidentally, in the present specification, the optical transmitter module and the optical receiver module are collectively referred to as an optical communication module.  
         [0006]      FIG. 1  is a partial cross-sectional view of an optical transmission module case storing an optical communication module. In  FIG. 1 , an optical communication module  300  is stored in an optical transmission module case  15  having a receptacle part  5  for connecting an optical transmission plug from the outside of the optical transmission module. The optical communication module  300  is provided inside with optical coupling surface  700  for optical coupling with a ferrule end of the optical transmission plug that is connected from the outside of the optical transmission module. In the case of a receptacle for an SC connector, the optical transmission module case  15  has a hook part  15   a  for holding the SC connector. An inner position of the hook part  15   a  is referred to as a mechanical reference surface. Further, the optical coupling surface through which light can be coupled and transmitted when the optical transmission plug and the optical communication module  300  are connected is referred to as an optical reference surface. The distance between the mechanical reference surface and the optical reference surface is 7.0±0.1 mm. This distance is referred to as E dimension. Although the optical transmission plug is not shown in  FIG. 1  for ease of illustration, the real E dimension is the distance between the inner position of the hook and the optical coupling surface of the optical communication module when the optical transmission plug is inserted into the optical transmission module. This is common to the whole description in this specification.  
         [0007]      FIG. 2  is a partial cross-sectional view of an optical transmission module case storing the optical communication module and a hook part. In  FIG. 2 , the optical communication module  300  is stored in an optical transmission module case  16 , together with the receptacle part  5  for connecting the optical transmission plug from the outside of the optical transmission module and a hook part  30  for holding the optical transmission plug. The difference between the optical transmission module of  FIG. 2  and the optical transmission module of  FIG. 1  is that the hook part is separate from the optical transmission module case or integrally formed therewith. The dimensional relationship in  FIG. 2  is the same as in  FIG. 1 .  
         [0008]      FIG. 3  is a partial cross-sectional view of an optical transmission module case storing an optical communication module for LC connector. In  FIG. 3 , an LC connector-type optical communication module  350  is stored in an optical transmission module case  17  having a receptacle part  7  for connecting an optical transmission plug from the outside of the optical transmission module. The optical communication module  350  is provided inside with optical coupling surface  750  for optical coupling with a ferrule end of the optical transmission plug that is connected from the outside of the optical transmission module. The LC connector has a hook mechanism for holding the optical transmission plug. The held position of the hook mechanism is referred to as the mechanical reference surface. Further, the optical coupling surface through which light can be coupled and transmitted when the optical transmission plug and the optical communication module  350  are connected is referred to as the optical reference surface. The distance between the mechanical reference surface and the optical reference surface is 9.95±0.05 mm. This distance is referred to as B dimension. 
    [Patent Reference 1] U.S. Pat. No. 6,071,016.     [Patent Reference 2] Japanese Patent Application Publication No. Hei 10-247740.     [Patent Reference 3] Japanese Patent Application Publication No. Hei 10-247742.     [Patent Reference 4] Japanese Patent Application Publication No. Hei 10-246839.     [Patent Reference 5] Japanese Patent Application Publication No. Hei 11-337770.     [Patent Reference 6] Japanese Patent Application Publication No. 2005-309028.     [Patent Reference 7] Japanese Patent Application Publication No. Hei 10-170759.     [Patent Reference 8] Japanese Patent Application Publication No. Hei 10-160966.     [Patent Reference 9] Japanese Patent Application Publication No. HEI 10-170763.      
         [0018]     The optical transmitter module or optical receiver module described in the above Patent References 1 to 3 is fixed to a case of the optical transmission module. Further, the optical transmission plug connected to the optical transmission module has an optical fiber at the back. In a device with the optical transmission module mounted thereon, a tensile force may be applied to the optical fiber in order to bundle many optical fibers. Because of the tensile force, stress is applied to the ferrule of the optical transmission plug, which is likely to prevent the light from being coupled or likely to cause damage of the optical transmitter module or optical receiver module.  
       SUMMARY OF THE INVENTION  
       [0019]     The present invention provides a receptacle-type optical transmission module that reduces the external influence of a tensile force on the optical fiber and maintains the optical coupling of the optical transmitter module or optical receiver module.  
         [0020]     The solution of the above described problems is achieved by an optical transmission module including: a communication module part for converting an electrical signal to an optical signal or converting an optical signal to an electrical signal; and a case for movably holding the communication module and having a hook part for positioning an optical plug that is connected to the communication module, wherein the distance in an optical axis direction between the hook part and an light coupling surface of the communication module part is in a predetermined range when the optical plug is connected to the optical communication module part.  
         [0021]     Further, it is achieved by an optical transmission module including: a transmission module part for converting an electrical signal to an optical signal or converting an optical signal to an electrical signal; and a case for holding the transmission module, wherein when an optical plug is connected to the communication module part and stress is applied to the optical plug, the communication module moves while maintaining optical coupling with the optical plug.  
         [0022]     Further, it is achieved by an optical transmission module including: a communication module part for converting an electrical signal to an optical signal or converting an optical signal to an electrical signal; and a case for movably holding the communication module, wherein when an optical plug is connected to the communication module part, the communication module is positioned by the optical plug. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0023]     Preferred embodiments of the present invention will now be described in conjunction with the accompanying drawings, in which;  
         [0024]      FIG. 1  is a partial cross-sectional view of an optical transmission module case storing an optical communication module;  
         [0025]      FIG. 2  is a partial cross-sectional view of an optical transmission module case storing the optical communication module and a hook part;  
         [0026]      FIG. 3  is a partial cross-sectional view of an optical transmission module case storing an optical communication module for LC connector;  
         [0027]      FIG. 4  is a perspective view illustrating the configuration of an optical transmission module;  
         [0028]      FIG. 5  is a partial cross-sectional view of the optical transmission module case storing the optical communication module movable in an optical axis direction;  
         [0029]      FIG. 6  is a partial cross-sectional view of the optical transmission module case storing the optical communication module movable in the optical axis direction and the hook part;  
         [0030]      FIG. 7  is a partial cross-sectional view of the optical transmission module case storing the optical transmission module which is movable in the X, Y, Z and θxy directions;  
         [0031]      FIG. 8  is a partial cross-sectional view of the optical transmission module case storing the optical communication module movable in the X, Y, Z and θxy directions and the hook part;  
         [0032]      FIG. 9  is a partial cross-sectional view illustrating the state where an optical transmission plug is connected to the optical transmission module case storing the optical communication module;  
         [0033]      FIG. 10  is a partial cross-sectional view showing that the optical transmission plug is connected to the optical transmission module case storing the optical communication module and the hook part;  
         [0034]      FIG. 11  is a partial cross-sectional view of an optical transmission module case storing the LC connector-type optical communication module which is movable in the Z direction;  
         [0035]      FIG. 12  is a partial cross-sectional view of the optical transmission module case storing the LC connector-type optical communication module which is movable in the X, Y, Z, and θxy directions;  
         [0036]      FIG. 13  is a partial cross-sectional view showing that an optical transmission plug is connected to the optical transmission module case storing the optical communication module for LC connector; and  
         [0037]      FIG. 14  is a partial cross-sectional view of the optical transmission plug to which a tensile force is applied and the optical transmission module. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0038]     Hereinafter, a mode for carrying out the invention will be described by way of embodiments with reference to the drawings. Incidentally, same parts are given same reference numbers and their description will not be repeated.  
       Embodiment 1  
       [0039]      FIG. 4  is a perspective view illustrating the configuration of an optical transmission module. In  FIG. 4 , an optical transmission module  1000  is configured to have an optical transmitter module  100 , an optical receiver module  200 , a printed board  50  in which control circuits for the respective modules  100 ,  200  are implemented, a receptacle part  5  for connecting an optical transmission plug not shown from the outside of the optical transmission module  1000 , and a hook part  30  for holding an optical transmission plug, all of which are stored between an upper case  10  and a lower case  20 .  
         [0040]      FIG. 5  is a partial cross-sectional view of the optical communication module case storing the optical communication module which is movable in an optical axis direction. In  FIG. 5 , the optical communication module  300  is stored in an optical transmission module case  15  having the receptacle part  5  for connecting the optical transmission plug from the outside of the optical transmission module. The optical communication module  300  and the optical transmission module case  15  have a distance DX therebetween parallel to the Z-axis, as well as “φA&lt;φR” and “φB&lt;φS” within the X-Y surface as the relations between the outer diameters of the optical communication module  300  and between the inner diameters of the transmission module case  15 . As a result, the optical communication module  300  can move backward and forward along the Z-axis which is the optical axis direction. In the case where the distance between the optical communication module  300  and the optical transmission module case  15  is “DX”, the distance between the mechanical reference surface and optical coupling surface  700  of the optical communication module  300  is “E-DX”.  
         [0041]      FIG. 6  is a partial cross-sectional view of the optical transmission module case storing the optical communication module movable in the optical axis direction and the hook part. In  FIG. 6 , the optical communication module  300  is stored in the optical transmission module case  16 , together with the receptacle part  5  for connecting the optical transmission plug from the outside of the optical transmission module and the hook part  30 . The difference between the optical transmission module of  FIG. 6  and the optical transmission module of  FIG. 5  is that the hook part is separate from the optical transmission module case or integrally formed therewith. The dimensional relationship and the movable direction in  FIG. 6  are the same as in  FIG. 5 .  
         [0042]     According to the present embodiment, it is possible to maintain the optical coupling of the optical transmission module as long as the amount of Z-direction deformation of the hook is equal to or less than DX, even if a tensile force to deform the hook in the −Z direction is applied in the state where the optical transmission plug is inserted therein. Thus it is possible to obtain a receptacle-type optical transmission module that reduces the external influence of a tensile force on the optical fiber in the −Z direction and maintains the coupling of light.  
       Embodiment 2  
       [0043]      FIG. 7  is a partial cross-sectional view of the optical transmission module case storing the optical transmission module which is movable in the X, Y, Z and θxy directions. In  FIG. 7 , the optical communication module  300  is stored in the optical transmission module case  15  having the receptacle part  5  for connecting the optical transmission plug from the outside of the optical transmission module. The optical communication module  300  and the optical transmission module case  15  have a distance therebetween. Compared with Embodiment 1, the value of the distance DX parallel to the Z-axis is increased and the values of “φR−φA” and “φS−φB” are also increased. As a result, the optical communication module  300  can move in the X and Y directions that are orthogonal to the Z-axis as the optical axis direction, in the Z direction as the optical axis direction and in the θxy direction as the rotation direction. These moving directions of the communication module are closer to the connector direction than a surface perpendicular to the optical axis.  
         [0044]      FIG. 8  is a partial cross-sectional view of the optical transmission module case storing the optical communication module movable in the X, Y, Z and θxy directions and the hook part. In  FIG. 8 , the optical communication module  300  is stored in the optical transmission module case  16 , together with the receptacle part  5  for connecting the optical transmission plug from the outside of the optical transmission module and the hook part  30  for holding the optical transmission plug. The difference between the optical transmission module of  FIG. 8  and the optical transmission module of  FIG. 7  is that the hook part is separate from the optical transmission module case or integrally formed therewith. The dimensional relationship and the moving direction in  FIG. 8  are the same as in  FIG. 7 .  
         [0045]      FIG. 9  is a partial cross-sectional view illustrating the state where an optical transmission plug is connected to the optical transmission module case storing the optical communication module. In  FIG. 9 , the optical communication module  300  movable in the X, Y, Z and θxy directions is stored in the optical transmission module case  15  having the receptacle part  5  for connecting an optical transmission plug from the outside of the optical transmission module. The optical communication module  300  and the optical transmission module case  15  have the distance “DX”. When an optical transmission plug  500  is connected through which light can be transmitted, the distance “DX” between the optical communication module  300  and the optical transmission module case  15  is zero. More specifically, “E-DX” is 7.0±0.1 mm. In the case where the outer shape accuracy of the optical transmission plug  500  or receptacle part  5  is fluctuated, the optical axis Z is corrected before the optical transmission plug  500  is completely inserted therein, so that a ferrule part  505  of the optical transmission plug  500  and the optical axis of the optical coupling surface  700  of the optical communication module  300  are aligned with each other.  
         [0046]      FIG. 10  is a partial cross-sectional view showing that the optical transmission plug is connected to the optical transmission module case storing the optical communication module and the hook part. In  FIG. 10 , the optical communication module  300  movable in the X, Y, Z and θxy directions is stored in the optical transmission module case  15  having the receptacle part  5  for connecting the optical transmission plug from the outside of the optical transmission module and the hook part  30  for holding the optical transmission plug. The optical communication module  300  and the hook part  30  have the distance “DX”. When the optical transmission plug  500  is connected through which light can be transmitted, the distance “DX” between the optical communication module  300  and the optical transmission module case  15  is zero. More specifically, “E-DX” is 7.0 mm±0.1 mm. In the case where the outer shape accuracy of the optical transmission plug  500  or receptacle part  5  is fluctuated, the optical axis Z is corrected before the optical transmission plug  500  is completely inserted therein, so that the ferrule part  505  of the optical transmission plug  500  and the optical axis of the optical coupling surface  700  of the optical communication module  300  are aligned with each other.  
         [0047]     According to the present embodiment, it is possible to maintain the optical coupling of the optical transmission module as long as the deformation amount of the hook is equal to or less than the amount with which the optical communication module and the case are in contact with each other, even if a tensile force to deform the hook is applied in the state where the optical transmission plug is inserted therein. Thus it is possible to obtain a receptacle-type optical transmission module that reduces the external influence of a tensile force on the optical fiber and maintains the coupling of light.  
       Embodiment 3  
       [0048]      FIG. 11  is a partial cross-sectional view of the optical transmission module case storing the LC connector-type optical communication module which is movable in the Z direction. In  FIG. 11 , the optical communication module  350  is stored in the optical transmission module case  17  having the receptacle part  7  for connecting the optical transmission plug from the outside of the optical transmission module. The optical communication module  350  and the optical transmission module case  17  have the distance “DX” in parallel to the Z-axis, as well as “φJ&lt;φM” and “φK&lt;φN” within the X-Y surface as the relations between the outer diameters of the optical communication module  350  and between the inner diameters of the transmission module case  17 . As a result, the optical communication module  350  can move backward and forward along the Z-axis which is the optical axis direction. When the distance between the optical communication module  350  and the optical transmission module case  17  is “DX”, the distance between the mechanical reference surface and optical coupling surface  750  is “B-DX”.  
         [0049]     According to the present embodiment, it is possible to maintain the optical coupling of the optical transmission module as long as the amount of Z-direction deformation of the hook is equal to or less than DX, even if a tensile force to deform the hook in the −Z direction is applied in the state where the optical transmission plug is inserted therein. Thus it is possible to obtain a receptacle-type optical transmission module that reduces the external influence of a tensile force on the optical fiber in the Z-direction and maintains the coupling of light.  
       Embodiment 4  
       [0050]      FIG. 12  is a partial cross-sectional view of the optical transmission module case storing the LC connector-type optical transmission module which is movable in the X, Y, Z and θxy directions. In  FIG. 12 , the optical communication module  350  is stored in the optical transmission module case  17  having the receptacle part  7  for connecting the optical transmission plug from the outside of the optical transmission module. The optical communication module  350  and the optical transmission module case  17  have a distance. Compared with Embodiment 3, the value of the distance DX parallel to the Z-axis is increased and the values of “φM−φJ” and “φN−φK” are also increased. As a result, the optical communication module  350  can move in the X, Y directions that are orthogonal to the Z-axis as the optical axis, in the Z direction as the optical axis, and in the θxy direction as the rotation direction. These moving directions of the communication module are the connector direction than a surface perpendicular to the optical axis.  
         [0051]      FIG. 13  is a partial cross-sectional view showing that an optical transmission plug is connected to the optical transmission module case storing the LC connector-type optical transmission module. In  FIG. 13 , the optical communication module  350  movable in the X, Y, Z and θxy directions is stored in the optical transmission module case  17  having the receptacle  7  for connecting the optical transmission plug from the outside of the optical transmission module. The optical communication module  350  and the optical transmission module case  17  have the distance “DX”. However, when an optical transmission plug  550  is connected through which light can be transmitted, the distance “DX” between the optical communication module  350  and the optical transmission module case  17  is zero. More specifically, “B-DX” is 9.95±0.05 mm. In the case where the outer shape accuracy of the optical transmission plug  550  or receptacle part  7  is fluctuated, the optical axis Z is corrected before the optical transmission plug  550  is completely inserted therein, so that a ferrule part  507  of the optical transmission plug  550  and the optical axis of the optical coupling surface  750  of the optical communication module  350  are aligned with each other.  
         [0052]      FIG. 14  is a partial cross-sectional view of the optical transmission plug to which a tensile force is applied and the optical transmission module. In  FIG. 14 , the optical communication module  350  movable in the Z, X, Y and θxy directions is stored in the optical transmission module case  17  having the receptacle part  7  for connecting the optical transmission plug from the outside of the optical transmission module. The optical communication module  350  and the optical transmission module case  17  have a distance. When the tensile force is applied to the optical transmission plug  550  connected to the optical communication module  350 , the ferrule  505  that is embedded in the optical transmission plug  550  or in the plug is inclined at the distance between the receptacle part  7  and the optical transmission plug  550 . The optical communication module  350  freely movable in the X, Y, Z, and θxy directions follows the optical transmission plug  550 . In this way the optical coupling surface  750  is maintained and thus the power for the optical transmission is maintained.  
         [0053]     According to the present embodiment, it is possible to maintain the optical coupling of the optical transmission module as long as the deformation amount of the hook is equal to or less than the amount with which the optical communication module and the case are in contact with each other, even if a tensile force to deform the hook is applied in the state where the optical transmission plug is inserted therein. Thus it is possible to obtain a receptacle-type optical transmission module that reduces the external influence of a tensile force on the optical fiber and maintains the coupling of light.  
         [0054]     According to the present invention, it is possible to provide a receptacle-type optical transmission module that reduces the external influence of a tensile force on the optical fiber and maintains the coupling of light of the optical transmitter module or optical receiver module.