Abstract:
An optical connector plug inserted into a receptacle of an optical communication module, having: an optical fiber; a ferrule having a tubular form, the optical fiber being provided in an inner hole of the ferrule; and a housing which is fitted into the receptacle, the optical fiber and the ferrule passing through the interior of the housing, wherein either one of at least a part of the housing and at least a part of the ferrule is made of an electromagnetic wave absorption material.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]     This application claims priority to Provisional Application filed on Jul. 28, 2005 by the same Applicant, which is hereby incorporated by reference in its entirety. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to an optical connector plug.  
         [0004]     2. Related Background Art  
         [0005]     An optical communication module comprises an optical transmission sub-assembly, an optical reception sub-assembly, a circuit board, a receptacle, and a casing. The optical transmission sub-assembly comprises a light-emitting element for generating light. The optical reception sub-assembly comprises a light-receiving element for receiving light. The circuit board carries a driver IC and so on, and is electrically connected to the light-emitting element and light-receiving element. The casing is provided to cover the optical transmission sub-assembly, optical reception sub-assembly, and circuit board. The receptacle comprises opening portions for optically coupling optical fibers to each of the light-emitting element and light-receiving element. An optical connector plug holding an optical fiber is inserted into the opening portion in the receptacle. A metallic casing is used in this type of optical communication module to prevent the emission of electromagnetic waves to the outside. This technology is disclosed in Japanese Unexamined Patent Application Publication No. 2004-212709, for example.  
       SUMMARY OF THE INVENTION  
       [0006]     However, with the optical communication module described above, electromagnetic waves are emitted to the outside through the opening portion in the receptacle and so on. Moreover, when the optical connector plug is inserted into the receptacle, faint electromagnetic waves may be subjected to stimulated emission from the interior of the optical communication module by the metallic components in the interior of the optical connector plug.  
         [0007]     An object of the present invention is to provide an optical connector plug and an optical connector device which are capable of suppressing electromagnetic wave emission from an optical communication module.  
         [0008]     An optical connector plug of the present invention is inserted into a receptacle of an optical communication module. The optical connector plug comprises an optical fiber, a ferrule, and a housing. The ferrule has a tubular form, and the optical fiber is provided in an inner hole thereof. The optical fiber and ferrule pass through the interior of the housing, and the housing is fitted into the receptacle. In this optical connector plug, at least a part of the housing or at least a part of the ferrule is comprised of an electromagnetic wave absorption material.  
         [0009]     An optical connector device of the present invention comprises: the first optical connector plug of the present invention; the second optical connector plug of the present invention; and an adapter connecting and holding the first optical connector plug and the second optical connector plug, wherein the adapter is comprised of an electromagnetic wave absorption material. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]      FIG. 1  is a perspective view of an optical connector plug according to an embodiment of the present invention.  
         [0011]      FIG. 2  is an exploded perspective view of the optical connector plug according to the embodiment of the present invention.  
         [0012]      FIG. 3  is a sectional view along a line III-III indicated by the arrow in  FIG. 1 .  
         [0013]      FIG. 4  is a sectional view showing a state in which the optical connector plug shown in  FIG. 3  is fitted into an optical communication module.  
         [0014]      FIG. 5  is a perspective view of an optical connector device according to an embodiment of the present invention.  
         [0015]      FIG. 6  is an exploded perspective view of the optical connector device according to the embodiment of the present invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0016]     A preferred embodiment of the present invention will be described in detail below with reference to the drawings. Note that identical reference symbols have been allocated to identical or corresponding parts in each of the drawings.  
         [0017]      FIG. 1  is a perspective view of an optical connector plug according to an embodiment of the present invention. In  FIG. 1 , an optical communication module is illustrated together with the optical connector plug. An optical connector plug  10  shown in  FIG. 1  is used to transmit an optical signal from an optical communication module  100  or to transmit an optical signal from the outside to the optical communication module  100 . Note that the optical connector plug according to this embodiment is an SC type optical connector plug, but the present invention is not limited to an SC type optical connector plug, and may be applied similarly to an MU type or LC type optical connector plug.  
         [0018]     The optical communication module  100  comprises an optical transmission sub-assembly  102 , an optical reception sub-assembly  104 , and a receptacle  106 . The optical transmission sub-assembly  102  is a device for outputting an optical signal, and comprises a light-emitting element such as a semiconductor laser. The optical reception sub-assembly  104  is a device for receiving an optical signal, and comprises a light-receiving element such as a photodiode.  
         [0019]     The optical communication module  100  further comprises a circuit board carrying a driver IC and the like for driving the light-emitting element. Hence, the optical communication module  100  generates electromagnetic waves from the internal elements thereof or from wiring and so on. To reduce the emission of these electromagnetic waves to the outside, the optical communication module  100  uses a metallic material which blocks electromagnetic waves for a casing or the like constituting the outer shell thereof.  
         [0020]     The receptacle  106  comprises an outer wall defining two holes. The optical transmission sub-assembly  102  and optical reception sub-assembly  104  are housed respectively in the two holes. The optical connector plug  10  is fitted into these holes in the receptacle  106 . As a result, an optical fiber of the optical connector plug  10  is optically coupled to the light-emitting element of the optical transmission sub-assembly  102  or the light-receiving element of the optical reception sub-assembly  104 .  
         [0021]     The optical connector plug  10  according to this embodiment will now be described in further detail.  FIG. 2  is an exploded perspective view of the optical connector plug according to this embodiment of the present invention.  FIG. 3  is a sectional view along a line III-III indicated by the arrow in  FIG. 1 .  FIG. 4  is a sectional view showing a state in which the optical connector plug shown in  FIG. 3  is fitted into an optical communication module.  
         [0022]     As shown in FIGS.  1  to  4 , the optical connector plug  10  comprises an optical fiber core wire  12 , a ferrule  14 , and a housing  16 .  
         [0023]     The optical fiber core wire  12  covers an optical fiber  12   a  (see  FIG. 3 ). The optical fiber core wire  12  is held by the ferrule  14 .  
         [0024]     The ferrule  14  comprises a ferrule core  14   a  and a flange portion  14   b.  The ferrule core  14   a  is a substantially cylindrical member. The optical fiber  12   a  passes through the inner hole in the ferrule core  14   a.  The ferrule core  14   a  of this embodiment is made of nickel(Ni). Note that the ferrule core  14   a  may be comprised of a ceramic such as zirconia.  
         [0025]     The flange portion  14   b  has a substantially cylindrical form. The flange portion  14   b  may be a metallic or resin member, but is preferably made of a resin having an electromagnetic wave absorption function. This resin material will be described in further detail below.  
         [0026]     The flange portion  14   b  is provided co-axially with the ferrule core  14   a.  The flange portion  14   b  comprises at one end side thereof a flange  14   c  having a larger diameter than the other part. The flange portion  14   b  holds a base end portion of the ferrule core  14   a  which is inserted into an inner hole in the end side of the flange portion  14   b.  The optical fiber core wire  12  passes through the inner hole in the flange portion  14   b  and extends from an opening in the other end of the flange portion  14   b.    
         [0027]     The housing  16  covers the optical fiber core wire  12  and ferrule  14 . The housing  16  comprises a plug frame  20 , a stop ring  22 , a first ring  24 , a second ring  26 , a boot  28 , and a cover  30 .  
         [0028]     The plug frame  20  is a tubular member. The plug frame  20  comprises a pair of side faces  20   a.  Each of the pair of side faces  20   a  includes a protruding portion  20   b.  The protruding portion  20   b  extends in a vertical direction in relation to the axis of the plug frame  20 . The side face  20   a  also includes an opposing surface  20   e  which opposes one surface of the protruding portion  20   b.    
         [0029]     The plug frame  20  further comprises an annular portion  20   c  which defines a hole having a smaller diameter than the other parts thereof in the axial direction of the plug flame  20 . In other words, the annular portion  20   c  extends inside in annular form toward the axis.  
         [0030]     The ferrule core  14   a  passes through an inner hole extending from the annular portion  20   c  to one end of the plug frame  20 . The flange portion  14   b  passes through an inner hole extending from the annular portion  20   c  to the other end of the plug frame  20 . A groove  20   d  is formed on an inner wall surface of the plug frame  20  defining the inner hole on the other end side. One end side of the stop ring  22  is inserted into the inner hole on the other end side of the plug frame  20 .  
         [0031]     The stop ring  22  is a substantially cylindrical member. The stop ring  22  is provided co-axially with the plug frame  20 . The stop ring  22  comprises a collar-shaped portion  22   a.  The collar-shaped portion  22   a  extends outside in annular form around the stop ring  22 . The collar-shaped portion  22   a  is inserted into the groove  20   d  of the plug frame  20 . Thus the stop ring  22  is latched to the plug frame  20 .  
         [0032]     A groove  22   b  is formed in an outer wall surface of the stop ring  22  further toward the other end side than the collar-shaped portion  22   a.  The stop ring  22  further comprises a large diameter inner hole and a small diameter inner hole in the axial direction thereof. A stepped surface  22   c  positioned at the boundary between the large diameter inner hole and the small diameter inner hole opposes one surface of the annular portion  20   c  of the plug frame  20 . The flange  14   c  and a spring  32  are provided between this surface of the annular portion  20   c  and the stepped surface  22   c.    
         [0033]     The spring  32  is a metallic coil spring. The flange portion  14   b  passes through the inside of the spring  32 . One end of the spring  32  abuts against the stepped surface  22   c.  The other end of the spring  32  abuts against the flange  14   c.  The urging force generated by the spring  32  causes the flange  14   c  to abut against one surface of the annular portion  20   c.    
         [0034]     The first ring  24  is attached to the other end side of the stop ring  22 . The first ring  24  is a substantially cylindrical member provided co-axially with the stop ring  22 . The first ring  24  is metallic, and may be formed from an aluminum alloy, for example.  
         [0035]     The first ring  24  comprises a large diameter portion  24   a  and a small diameter portion  24   b  sequentially in the axial direction of the first ring  24 . The other end side of the stop ring  22  is fitted into an inner hole in the large diameter portion  24   a.    
         [0036]     The optical fiber core wire  12  covered by a tube  34  passes through the inner hole in the first ring  24 . The small diameter portion  24   b  of the first ring  24  tightens the tube  34  to the optical fiber core wire  12 .  
         [0037]     The second ring  26  is provided so as to cover the small diameter portion  24   b  of the first ring  24 . The second ring  26  is a cylindrical member provided co-axially with the small diameter portion  24   b  of the first ring  24 . The second ring  26  is metallic, and may be formed from a copper alloy, for example.  
         [0038]     The boot  28  is provided so as to cover the first ring  24  and the second ring  26 . The optical fiber core wire  12  covered by the tube  34  passes through the inside of the boot  28 .  
         [0039]     A claw  28   a  is provided at the end of the boot  28 . The claw  28   a  is inserted into the groove  22   b  of the stop ring  22  such that the boot  28  is latched to the stop ring  22 .  
         [0040]     The cover  30  is a tubular member provided so as to cover the plug frame  20 , stop ring  22 , first ring  24 , second ring  26 , and a part of the boot  28 .  
         [0041]     The cover  30  comprises a pair of side walls  30   a,  an upper wall  30   b  which extends along a plane that intersects the side walls  30   a,  and a lower wall which opposes the upper wall  30   b.  A protrusion  30   d  is provided on the upper wall  30   b.  When the optical connector plug  10  is inserted into the receptacle  106 , the protrusion  30   d  is guided along a groove  106   a  in the receptacle  106  (see  FIG. 1 ). Note that the groove  106   a  is provided in the outer wall of the receptacle  106  at a predetermined length from the open end.  
         [0042]     The side walls  30   a  of the cover  30  are each provided with a groove  30   e.  The protruding portion  20   b  of the plug frame  20  is inserted into the groove  30   e.    
         [0043]     Of the housing  16  comprised as described above, in this embodiment the plug frame  20 , stop ring  22 , and cover  30  are comprised of a material having an electromagnetic wave absorption function. The flange portion  14   b  is also comprised of a material having an electromagnetic wave absorption function. Note that the boot  28  and tube  34  may also be comprised of a material having an electromagnetic wave absorption function.  
         [0044]     A material containing resin as a main raw material and an additive having electromagnetic wave absorbency may be used as a material having electromagnetic wave absorbency. Examples of the resin include nylon resin, PBT resin, PPS resin, LCP resin, PEEK resin, and epoxy resin.  
         [0045]     As the additive, a fine powder of iron, a fine powder of aluminum, a fine powder of cobalt, a fine powder of silicon, a fine powder of iron oxide, a fine powder of carbon, or a fine powder of stainless steel may be used. Alternatively, a fine powder of an alloy containing two or more materials selected from iron, aluminum, cobalt, and silicon may be used as the additive. These additives are capable of absorbing electromagnetic waves by converting the electromagnetic waves into heat.  
         [0046]     The optical connector plug  10  is capable of suppressing electromagnetic waves generated by the optical communication module  100 . The structure of the receptacle  106  of the optical communication module  100  to which the optical connector plug  10  is attached will now be described in detail.  
         [0047]     As illustrated in  FIGS. 3 and 4 , the receptacle  106  comprises an outer wall  110  which defines the hole for inserting the optical connector plug  10 . The outer wall  110  is made of metal or resin having a metal film formed on its surface.  
         [0048]     A pair of latching members  112  extending in the axial direction of the receptacle  106  are provided in the interior of the receptacle  106 . A claw  112   a  is provided at the tip end of each latching member  112 . When the optical connector plug  10  is inserted into the receptacle  106 , the claw  112   a  is inserted between one surface of the protruding portion  20   b  and the opposing surface  20   e  of the plug frame  20 , and thereby latches the optical connector plug  10 .  
         [0049]     In the receptacle  106 , a sleeve assembly  114  of one of the optical transmission sub-assembly  102  and the optical reception sub-assembly  104  is inserted into one of the openings in the outer wall  110 . The sleeve assembly  114  seals one of the openings in the outer wall  110 .  
         [0050]     The sleeve assembly  114  comprises a first sleeve  116 , a bush  118 , a stub  120 , and a second sleeve  122 . The first sleeve  116  is a cylindrical member possessing elasticity in the diametrical direction. The first sleeve  116  is formed from a ceramic. The ferrule core  14   a  is inserted into an inner hole in the first sleeve  116 .  
         [0051]     The bush  118  is a cylindrical member, and a base end portion of the first sleeve  116  is fitted into an inner hole of the bush  118 . A part of the stub  120  is inserted into the base end portion of the first sleeve  116 . The bush  118  also holds a base end portion of the stub  120 . The stub  120  holds an optical fiber.  
         [0052]     The second sleeve  122  is a cylindrical member covering the first sleeve  116  and a part of the bush  118 . The second sleeve  122  and bush  118  are metallic members which seal one of the openings in the outer wall  110 .  
         [0053]     When the optical connector plug  10  is inserted into the hole in the receptacle  106  structured described above, the ferrule core  14   a  is fitted into the first sleeve  116 . As a result, the optical fiber of the stub  120  is optically coupled to the optical fiber  12   a  held in the ferrule core  14   a.    
         [0054]     Simultaneously, the opening in the receptacle  106  is sealed by the housing  16 . The plug frame  20 , stop ring  22 , and cover  30  of the housing  16  have an electromagnetic wave absorption function, and hence the opening in the receptacle  106  is also sealed electromagnetically. Thus the emission of electromagnetic waves from the receptacle  106  is suppressed.  
         [0055]     Further, a metallic component of the optical connector plug  10  such as the spring  32  is covered by the plug frame  20 , stop ring  22 , and cover  30  which have an electromagnetic wave absorption function. Hence, stimulated emission of electromagnetic waves by the metallic component of the optical connector plug  10  is suppressed.  
         [0056]      FIG. 5  is a perspective view of an optical connector device according to an embodiment of the present invention.  FIG. 6  is an exploded perspective view of the optical connector device according to the embodiment of the present invention. In  FIGS. 5 and 6 , an optical connector device is illustrated. An optical connector device  50  shown in  FIGS. 5 and 6  is used to transmit an optical signal from an optical communication module  100  shown in  FIG. 1  or to transmit an optical signal from the outside to the optical communication module  100 .  
         [0057]     The optical connector device  50  comprises the first optical connector plug  10 , the second optical connector plug  10  and an adapter  60  connecting and holding the first optical connector plug  10  and the second optical connector plug  10 . The adapter  60  is comprised of an electromagnetic wave absorption material. The adapter  60  has a first holding part  60   a  to hold the first optical connector plug  10  and a second holding part  60   b  to hold the second optical connector plug  10 .  
         [0058]     Since the first optical connector plug  10  and the second optical connector plug  10  are held by the adapter  60 , it is easy to insert and remove the optical connector device  50  from the optical communication module  100 .  
         [0059]     Note that the present invention is not limited to the embodiment described above, and may be subjected to various modifications. For example, in the embodiment described above, the plug frame  20 , stop ring  22 , and cover  30  have an electromagnetic wave absorption function, but any one of these components, or a part or all of the other components constituting the housing, may possess an electromagnetic wave absorption function.  
         [0060]     As described above, when the optical connector plug is inserted into the receptacle, an opening in the receptacle is electromagnetically sealed by the housing, which includes an electromagnetic wave absorbent. As a result, the emission of electromagnetic waves from the opening in the receptacle is suppressed. Furthermore, since the electromagnetic waves emitted from the optical communication module are absorbed into the housing, stimulated electromagnetic wave emission is suppressed even when the interior of the optical connector plug comprises a metallic component.  
         [0061]     The electromagnetic wave absorption material is preferably comprised of a resin containing an additive that has electromagnetic wave absorbency. By adding an additive to a malleable resin, a housing having an electromagnetic wave absorption function can be provided at low cost.  
         [0062]     The additive may be a fine powder of iron, iron oxide, carbon, or stainless steel, or a fine powder of two or more materials selected from iron, aluminum, cobalt, and silicon. Note that the additive may be a fine powder of aluminum, cobalt, or silicon.  
         [0063]     The ferrule is preferably comprised of a material containing nickel(Ni) as a main component. With this constitution, the nickel ferrule reflects electromagnetic waves into the interior of the optical communication module, and hence the emission of electromagnetic waves from the opening in the receptacle can be further suppressed.  
         [0064]     According to the present invention, an optical connector plug which is capable of suppressing electromagnetic wave emission from an optical communication module is provided.