Abstract:
An optoelectronic transmitting and/or receiving module and an optical plug include a circuit carrier disposed at least partially in an alignment parallel to the optical axis of the module in a module housing. The circuit carrier forms a tongue-shaped region that protrudes into the continuation. A transmitting device and/or a receiving device is disposed in the continuation, where they are connected to the circuit carrier. The associated axial offsetting of the transmitting device and/or receiving device in the direction of an optical plug to be coupled on permits the provision of plug-in connections with improved protection of the devices and the fiber ends.

Description:
BACKGROUND OF THE INVENTION 
   Field of the Invention 
   The invention relates to an optoelectronic transmitting and/or receiving module. In addition, the invention relates to a circuit carrier, a module housing, and an optical plug, which is preferably used in conjunction with or as part of an optoelectronic module. A preferred application area of the invention is that of low-cost optoelectronic modules that are coupled to POF (Plastic Optical Fiber) optical waveguides. Within this preferred application area, the invention is suitable in particular for use in multimedia networks in the in-house sector and in the automotive sector. 
   German Published, Non-Prosecuted Patent Application No. DE 199 09 242 A1, which corresponds to U.S. Pat. No. 6,309,566, discloses an optoelectronic module in which a support with an optoelectronic transducer is positioned in a module housing and is encapsulated in a translucent, moldable material. Coupling in or out of light takes place via an optical fiber that is coupled to a stub of the module housing. On the support, there is also the driver device or receiving device for the optoelectronic transducer. 
   It is desirable to construct a plug-in connection between an optical plug and a transceiver in such a way that on the one hand the greatest possible degree of electromagnetic shielding is provided and on the other hand the fiber end face is not soiled and is reliably protected even in the event of inadvertently incorrect plugging, or what is known as “blind” plugging. Known for this purpose is the so-called “kojiri” criterion, on the basis of which the fiber is protected in the manner of a “sword sheath” (Japanese: kojiri) in such a way that the fiber can only emerge from the protective surrounding once the plug has been inserted into guiding grooves of the assigned plug housing and positions itself in front of the corresponding transducer without soiling. This has until now been realized by using a movable kojiri guard, which however entails increased expenditure. 
   SUMMARY OF THE INVENTION 
   It is accordingly an object of the invention to provide an optoelectronic transmitting and/or receiving module, a circuit carrier, a module housing, and an optical plug that overcome the hereinafore-mentioned disadvantages of the heretofore-known devices of this general type and that make it possible to provide a high degree of electromagnetic shielding and at the same time to protect the optical fiber of a plug to be coupled to the optoelectronic module reliably from soiling and damage. 
   With the foregoing and other objects in view, there is provided, in accordance with the invention, an optoelectronic transmitting and/or receiving module. The optoelectronic module includes a transmitting and/or receiving device, an electrical wiring device, a circuit carrier, and a module housing. The transmitting and/or receiving device has an optical axis. The electrical wiring device connects to the transmitting device. The circuit carrier connects to the transmitting device, supports the transmitting device and the electrical wiring device, and forms a tongue-shaped region. The module housing holds the circuit carrier at least partially parallel to the optical axis and has a continuation extending in a direction of the optical axis of the transmitting device. The continuation is configured to couple to an optical plug and has the tongue-shaped region and the transmitting device extending therein. 
   With the objects of the invention in view, there is also provided an optical plug for an optoelectronic module. The optical plug includes a plug housing, an optical fiber, and a latching device. The plug housing has an extreme end and a fixed peripheral guard wall formed at the extreme end. The optical fiber has an end face. The end face projects within the extreme end of the plug housing and is protected by the peripheral guard wall. The latching device connects the optical plug to a mating coupling part. 
   The invention is distinguished by the fact that a circuit carrier, which is disposed in a module housing and bears a transmitting device and/or a receiving device and assigned wiring devices, is disposed in an alignment parallel to the optical axis of the transmitting device or receiving device in the module housing. In this case, the circuit carrier forms a tongue-shaped region, which protrudes into a continuation of the module housing serving for the coupling on of an optical plug. The transmitting device and/or receiving device is disposed in the continuation, where it is connected to the circuit carrier, consequently is installed in the module housing such that it is offset in the axial direction. 
   The axial displacement of the transmitting device and/or receiving device into the coupling continuation of the module housing, and consequently in the direction of an optical plug to be coupled on, makes it possible to couple onto the optoelectronic module an optical plug that is provided with a fixed kojiri guard and for this purpose forms a fixed, peripheral guard wall that projects beyond the end face of the optical fiber in a protective manner. In the case of the configuration of the transceiver according to the invention, such a kojiri guard wall extends beyond the transmitting device or receiving device, in that it encloses the continuation of the module housing, with the result that a complete four-sided kojiri guard is achieved. 
   If the peripheral guard wall includes an electrically conductive material, the transmitting and/or receiving device is also additionally shielded electromagnetically by the projecting plug guard wall, so that interfering radiation emitted is reduced considerably. 
   The solution according to the invention is consequently based on the idea of disposing the transmitting or receiving device of an optoelectronic module in the continuation of the module housing serving for the coupling on of an optical plug. This is technically realized on the one hand by an alignment of the circuit carrier parallel to the optical axis of the module housing and on the other hand by a tongue-shaped region of the circuit carrier, which protrudes into the continuation, with the result that the transmitting device or receiving device in the continuation can be mounted on the circuit carrier. 
   In a preferred configuration of the invention, the continuation is cylindrically formed, although in principle other shapes such as a rectangular form are also conceivable. 
   The transmitting device and/or receiving device are preferably respectively disposed in a device housing, which preferably includes a transparent encapsulating material. In a first variant, the device is disposed on a leadframe that is cast into the device housing or transparent encapsulating material, the terminal contacts of the leadframe protruding laterally from the device housing. As an alternative, the device housing does not need a leadframe and the transmitting device and/or receiving device have electrical terminal contacts on the rear side of the device housing. In particular, a so-called TSLP (Thin Small Leadless Package) construction technology is preferably used for this purpose. 
   The circuit carrier may include a solid, non-flexible material, for example an FR-4 board. As an alternative, the circuit carrier is a flexible circuit carrier, for example a flex board. In the first case, the transmitting component preferably has a leadframe and is flattened on its contact side toward the circuit carrier, in order to permit fastening on the circuit carrier. The terminal contacts of the leadframe may in this case protrude straight out and penetrate the circuit carrier or be bent away laterally. 
   A flexible circuit carrier with a device housing with electrical terminal contacts disposed on the rear side is preferably used. The device housing in this case electrically bonds the circuit carrier with its contacts that are disposed on the rear side and are configured parallel to the optical axis. In the region in which the transmitting device or receiving device is disposed, the flexible circuit carrier is angled away by ninety (90) degrees. In the case of this variant, the device housing advantageously has the same shape as the continuation of the module housing. A lateral clearance on the device housing, as in the case of the configuration with a leadframe in conjunction with a solid board, is not required. 
   The module housing is preferably formed such that it is open on at least one side, this side being closed after mounting of the circuit carrier by at least one side part that covers over the circuit carrier. To improve the electromagnetic shielding, the module housing preferably has electrical shielding and, for this purpose, is formed in particular from an electrically conducting material, in particular an electrically conducting plastic. Furthermore, it is preferably provided that the interior of the module housing is filled with a likewise electrically conductive encapsulating material. In order to prevent electrical short-circuits, the circuit carrier is protected from the encapsulating material, at least in the region of the devices and the electrical bonding contacts, for instance by a covering. 
   The device housing is preferably formed such that it is circular or rectangular in section. A rectangular configuration is particularly preferred in the cases in which the device is produced together with the device housing on a wafer. The device housing is then prepared by sawing out with a wafer saw. 
   Preferably, both the continuation of the module housing and the device housing and/or the transmitting or receiving device have structures that permit self-adjusting mounting of the device in the continuation. This involves for example stop structures on the device housing. 
   In a further preferred configuration, it is envisaged to dispose in the continuation of the module housing an elastic deforming body. The elastic deforming body resilient mounts the device housing in the continuation. When there is pressure of an assigned optical fiber of an optical plug on the transmitting or receiving module, the latter can yield rearward, the elastic deforming body producing a restoring force, in order that a fixed contact is maintained (butt coupling) and consequently the device housing is positioned against a front stop after the plug is pulled out. In this way, it is possible to keep to a minimum the gap between the end face of an optical fiber and the device housing or light-guiding structures formed in the latter, such as a lens, in order to minimize coupling losses. 
   The module housing with the components explained is preferably disposed in a surrounding housing for the transceiver (often referred to as a header). Such a surrounding housing preferably has a first region, which receives the module housing, and a second, axially offset region, which provides a receiving opening for an optical waveguide to be coupled on of an optical plug. Preferably provided in this case in the second region of the surrounding housing is a snap mechanism that permits a latching connection of the surrounding housing to a plug to be coupled on. Furthermore, it is preferably provided that the first region and the second region of the surrounding housing are separated from each other by a dividing wall. The dividing wall has in this case an opening through which the continuation of the module housing protrudes into the second region and in a corresponding way can be coupled to an optical plug. 
   In a preferred configuration of the module housing, at least one fixing pin, which is mounted in the module housing in corresponding openings and passes through the module housing, is provided. This serves for exact positioning of the module housing in the surrounding housing and on an assigned main circuit board. The fixing pin is preferably formed in an electrically conducting, in particular metallic, manner, with the result that induced electromagnetic currents in the interior of the module housing can flow away via it. 
   The module according to the invention is preferably an optoelectronic transceiver with a transmitting device and a receiving device that are respectively disposed in continuations of the module housing that are spaced apart from each other. The circuit carrier is in this case preferably formed in a U-shaped manner and has three regions. A first bottom region is provided with terminal contacts for the electrical bonding of the circuit carrier with a main circuit board. A first side region is angled away by 90 degrees with respect to the bottom region and bears the transmitting device and the associated wiring device. A second region is likewise angled away by 90 degrees with respect to the bottom region and bears the receiving device and the associated wiring device. 
   The optical plug according to the invention is characterized by the features that a plug housing forms at the extreme end a fixed, peripheral guard wall which projects in a protective manner beyond the end face of the optical fiber. In this way, the end face of the optical fiber is reliably protected from damage and soiling even in the event of inadvertent incorrect plugging or so-called “blind” plugging, as occurs in particular in the automotive sector. When the optical plug is inserted into an electrooptical module according to claim  1 , the projecting guard wall couples with the continuation of the module housing, the projecting guard wall extending over the transmitting device or receiving device and accordingly providing in the case of a metallic configuration an additional electromagnetic shielding, in any event an additional mechanical guard. 
   Latching devices of the plug preferably have a latching edge for the latching engagement of a latching element of a mating coupling part, movable clamping elements for the securing of a latching engagement and a movable plug release, the movable plug release allowing the movable clamping elements to be actuated. The plug release, the clamping elements and the latching element of the mating coupling part in this case preferably interact in such a way that, when the plug release is actuated, first of all the clamping elements are pivoted away laterally from the latching element and subsequently the latching element is raised above the locking edge. 
   It may also be provided that the plug release on the one hand has beveled lateral edges, which interact with edges formed on the underside of the clamping lobes when the plug release is actuated, and on the other hand has trapezoidal elevations, that have the effect of raising a latching element of a mating coupling part which is to be unlatched. 
   Other features that are considered as characteristic for the invention are set forth in the appended claims. 
   Although the invention is illustrated and described herein as embodied in an optoelectronic transmitting and/or receiving module, a circuit carrier, a module housing, and an optical plug, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims. 
   The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS: 
       FIG. 1A  is a lateral sectional view showing a first embodiment of a transmitting device disposed on a leadframe and in a transparent casting compound; 
       FIG. 1B  is a plan view of the transmitting device shown in  FIG. 1A ; 
       FIG. 1C  is a perspective view of the transmitting device shown in  FIG. 1A ; 
       FIG. 2  is a side view showing a module housing with a cylindrical continuation, the module housing being represented in a laterally open form and containing a circuit carrier and the transmitting device according to  FIG. 1 ; 
       FIG. 3  is a circuit diagram showing an opened representation of a circuit carrier with two side regions, which respectively form a tongue-shaped region connected to a transmitting device or a receiving device; 
       FIG. 4A  is a partial schematic and partial diagrammatic front view of a second embodiment of a transmitting device, the transmitting device being formed using TSLP technology; 
       FIG. 4B  is a partial schematic and partial diagrammatic front view of a receiving device using TSLP construction technology; 
       FIG. 5A  is a front view showing the transmitting device of  FIG. 4B  in a cylindrical continuation of a module housing; 
       FIG. 5B  is a lateral sectional view showing the receiving device of  FIG. 5A ; 
       FIG. 5C  is a front view showing the transmitting device of  FIG. 4A  in a cylindrical continuation of a module housing; 
       FIG. 5D  is a lateral sectional view showing the transmitting device of  FIG. 5C ; 
       FIG. 5E  is a sectional view showing a second embodiment of a transmitting or receiving device in a cylindrical continuation of a module housing; 
       FIG. 5F  is a lateral sectional view showing the transmitting or receiving device of the configuration of  FIG. 5   b;    
       FIG. 5G  is a front view showing the transmitting device of the configuration of  FIG. 5E ; 
       FIG. 6  is a circuit diagram a second embodiment of a circuit carrier, the circuit carrier being formed as a flex board and the tongue-shaped regions connected to a transmitting device or a receiving device being angled away by 90 degrees with respect to the plane of the figure in the connecting region; 
       FIG. 7  is a front view showing a configuration of a module housing of an optoelectronic transceiver according to FIGS.  2  and  5 A– 5 E in a surrounding housing and disposed on a main circuit board; 
       FIG. 8  is a front view showing the module housing of  FIG. 7  after attaching additional side covers and without showing the surrounding housing; 
       FIG. 9  is a rear view showing the module housing of  FIGS. 7 and 8  after mechanical fixing in the surrounding housing; 
       FIG. 10  is a sectional view through the surrounding housing of  FIGS. 7 and 9  parallel to the longitudinal axis of the surrounding housing, the surrounding housing forming a first region and a second region; 
       FIG. 11  is a bottom view showing an optical plug with two optical fibers, the end faces of which are set back from the front side of the plug; 
       FIG. 12  is a lateral sectional view showing the transceiver represented in  FIGS. 1 to 10  with an inserted plug according to  FIG. 11 ; 
       FIG. 13  is a sectional view of the plug of  FIG. 11  with a latching pawl of the surrounding housing engaging the plug; 
       FIG. 14  is a sectional view showing the plug of  FIGS. 11 to 13  without the plug release being represented; and 
       FIG. 15  is a sectional view showing a representation of the plug release of the plug of  FIGS. 11 to 14 . 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring now to the figures of the drawings in detail and first, particularly to  FIG. 1  thereof, there is shown an I/O transducer device  1 , which has a light-emitting transmitting device  2  disposed on a leadframe  3 . The transmitting device  2  is in particular a semiconductor laser or a light-emitting diode. The transmitting device is electrically bonded in the customary way via the leadframe. The transmitting device  1  and the leadframe  3  are disposed in a housing  4 , which is formed from an optically transparent encapsulating material. 
   In this case, a coupling lens  41  is disposed in the encapsulating material in the optical path of rays of the transmitting device  2 . Furthermore, the extreme end  42 , neighboring the coupling lens  41 , of the device housing  4  forms a fiber stop face for the fiber end face of an optical fiber to be coupled. 
     FIG. 1C  shows two terminal contacts  31 ,  32  of the leadframe  3 . The optical axis of the transducer device is identified by reference numeral  5 . It is pointed out that the vertex of the coupling lens  41  is slightly offset axially with respect to the fiber stop face  42 . 
   As represented in  FIGS. 1B and 1C , the device housing  4  is not formed in a completely circular manner but is flattened to its contact side  43  toward a circuit carrier. This permits the configuration in a cylindrical continuation, as represented in the following  FIG. 2 . 
   A receiving element, which is formed in particular as a monitor diode, may also be formed in a corresponding way. 
   Also represented in  FIG. 2 , in a side view, is a module housing  6 , which is also referred to as a CAI (Cavity as Interface) housing, which forms a main housing region  61  and a cylindrical continuation (which may also be referred to as an extended tube)  62 . In the module housing, there is a circuit carrier  7 , which has a tongue-shaped region  71 , which protrudes into the cylindrical continuation  62  of the module housing  6 . The tongue-shaped region  71  serves for the fastening of the transducer device  1  according to  FIG. 1 . The lateral representation of  FIG. 2  reveals the terminal contacts  31 ,  32 , by which the transducer module  2  is electrically connected to the circuit carrier  7  (i.e. a circuit board). Due to the described flattening of the transducer module  1 , it is possible in spite of the configuration of the tongue-shaped region  71  of the printed circuit board  7  for the transducer module to be disposed in the continuation  62  in such a way that its optical axis  5  lies on the optical axis of the cylindrical continuation. 
   Disposed on the circuit board  7 , in the main region  61  of the module housing  6 , are wiring devices, which represent in particular a driving circuit for the transmitting device or a receiving circuit for a receiving element. In addition, conductor tracks are formed in the customary way on the printed circuit board. 
     FIG. 3  shows a circuit carrier, which is used in an optoelectronic transceiver in which the module housing  6  has both a cylindrical continuation for a transmitting device and a cylindrical continuation for a receiving device. 
   The circuit carrier  7  is disposed in a U-shaped manner and has a bottom part  72  and two side parts  73 ,  74 . In the representation of  FIG. 3 , the three parts  72 ,  73 ,  74  are spread out flat. The bending locations  75  between the bottom part and the respective side parts are provided with a kind of perforation in order to improve the bendability. The bottom part  72  has electrical contacts  721  for the electrical bonding of a main circuit board, onto which the bottom part  72  is mounted. The two side parts  73 ,  74  respectively have a wiring device  81  for a transmitting element of an I/O transducer device  1  and a wiring device  82  for a transmitting element of an O/I transducer device  9 . 
   The two transducer modules  1 ,  9  are respectively disposed on the tongue-shaped regions  71   a ,  71   b  of the respective side part  73 ,  74  protruding into a cylindrical continuation. 
   Adjustment holes  722  made in the bottom part serve for the assembly of the transceiver and the fixing in a surrounding housing by using pins and also for the passive alignment with respect to the main circuit board, as still to be explained. 
   It is pointed out that the signaling and electrical bonding represented in  FIG. 3  are to be understood as given only by way of example. 
   It is further pointed out that the bottom part is preferably formed as a flexible foil, while the side parts  72 ,  74  are formed as solid side boards, in particular FR4 side boards. 
     FIG. 4A  shows an exemplary embodiment of an I/O transducer device  1 ′ as an alternative to that of the representation of  FIG. 1 . The transducer device is produced here using TSLP (thin smaller leadless package) technology. A transmitting device  2  is in turn encapsulated in a device housing  4  that includes a transparent encapsulating material with an integrated lens  41 . However, no leadframe is provided for the electrical bonding of the transmitting device  2 , but instead two electrical terminals  10   a ,  10   b , which are disposed on the rear side of the transducer device  1 ′. 
   The production of an I/O transducer using TSLP technology takes place in a way known per se by firstly a multiplicity of transducers being disposed on a conducting board, for example a copper plate, and bonded. The regions of the printed circuit board that are not required are then etched away, so that the contacts on the rear side are formed. Before the etching operation, encapsulation of the transducers in a transparent casting material is performed. At the end of the production process, there is individual separation. 
     FIG. 4B  shows a construction corresponding to  FIG. 4A  for an O/I transducer component  9 ′. A receiving device  11  is electrically bonded via electrical terminals  10   a ,  10   b  and is encapsulated in an encapsulating body  4  with an integrated, light-shaping element  41 . 
     FIGS. 5A–5D  shows the basic installation of a transducer device into the cylindrical continuation of a module housing, only the continuation  62  of the module housing being represented for the sake of better overall clarity. The representation shows, in parallel configuration, a first continuation  62   a , in which a receiving transducer device is disposed, and a continuation  62   b , in which a transmitting transducer device is disposed. The transducers are embodied in the TSLP type of construction according to  FIG. 4 . 
   It is pointed out here that the transducer devices are configured in a rectangular manner, as illustrated in the right-hand representation of  FIGS. 5B and 5D , which show views in the direction of the optical axis. The transducer devices are in this case individually separated after production in a simple way by using a wafer saw. The edge length of the transducer devices is dimensioned such that the transducer device is in bearing contact at its corners in the cylindrically configured continuation or extended tube  62 . This is irrespective of whether the transceiver is constructed for so-called SMI plugs (inner cylinder 25 mm) or for the automotive sector (inner cylinder 29 mm). 
   For the resilient mounting of the transducer device  1 ,  9 , an elastic deforming body is disposed between the transducer device  1 ,  9  and a stop of the cylindrical continuation. A fiber ferrule to be coupled on is inserted into the receiving region  13  of the continuation  62  and comes up against the fiber stop face  41 , described with respect to  FIG. 1 , and also a stop face  63  formed in the continuation  62 . When there is pressure of the inserted fiber ferrule on the transducer device, the latter can yield rearward because of the elastic deforming body  12 . At the same time, the elastic deforming body  12  produces a restoring force, in order that close contact is maintained (butt coupling). In this way, a high-quality coupling with low coupling losses is provided. 
     FIG. 5E  shows the installation of an alternatively configured transducer device into the cylindrical continuation  62  of a module housing  6 . The module housing is represented in full in  FIG. 5E . 
   The alternatively configured module device is represented in  FIGS. 5F and 5G . According to this, a transmitting component  2  (alternatively a receiving component) and electrical contacts  10   a ,  10   b  for the connection with a circuit board are in turn disposed in an encapsulating material  4 . Additionally provided is a passive adjusting structure  44 , which is aligned precisely with respect to the coupling lens  41  and the transmitting device  2  (or a receiving device) and serves for the exact fitting and automatic adjustment of the transducer device  1 ″ into the continuation or extended tube  62  of the module housing. Consequently,  FIG. 5E  reveals that the passive adjusting structure comes into bearing contact with a corresponding clearance  641  of a central web  64  of the continuation  62 . In this case, the central web  64  forms a fiber stop face  642 . The central web  64  has an opening, which is formed symmetrically with respect to the optical axis and through which the coupling lens  41  protrudes. The lens vertex in this case remains back from the fiber stop face  642  by about 50 μm. 
   The passive adjusting structure  44  can be aligned very precisely with respect to the lens and the transducer component  2 , since the structure is structured during the production process and for this purpose is, for example, integrated into a production mold. 
     FIG. 6  shows a circuit carrier corresponding to the circuit carrier represented in  FIG. 3 . The only differences are concerned with the fact that the circuit board  7  is completely formed as a flexible foil. The transducer devices  1 ,  9  represented are in a TSLP configuration, with the result that the terminal contacts are configured parallel to the optical axis. The transducer devices  1 ,  9  are disposed at subregions of the respective tongue-shaped region  71   a ,  71   b  which are angled away perpendicularly with respect to the plane of the drawing. The transducer components  1 ,  9  accordingly do not need to form a flattened contact side and may completely fill the interior space of the cylindrical continuation of the module housing. 
   The contacts  721  of the central or bottom part  72  are formed as SMD contacts. As an alternative, the contacts may also be realized as plug-in contacts. 
   The signaling represented is in turn only to be understood as given by way of example. 
     FIG. 7  shows the optoelectronic module described in  FIGS. 1 to 6 , disposed in a surrounding housing (also known as a header)  14 , which has a front plug receptacle, represented in  FIG. 10 . The sectional representation illustrated runs perpendicularly with respect to the optical axes of the transmitting and receiving device. It reveals well the circuit carrier  7 , represented in  FIGS. 3 and 6  and now bent in a U-shaped manner, the bottom region  72  of which is connected to a main circuit board  15 . The U-shaped installation of the circuit carrier  7  makes it possible to configure the electrical contacts by using lithography. In the exemplary embodiment represented, the electrical terminals are configured as plug-in contacts  723 . 
   Likewise revealed well in  FIG. 7  are the two wiring devices  81 ,  82 , which are disposed on the circuit board. The transducer devices  1 ,  9  are represented in a front view. The transmitting device or receiving device lies behind the plane of the drawing and cannot be seen. In the case of the configuration of  FIG. 7 , the transducer devices  1 ,  9  are formed in a way corresponding to the configuration of  FIG. 1 , i.e. with a flattening toward the contact side, which can likewise be seen. 
   Also provided is a metallic pin  16 , which is mounted in a corresponding opening  141  of the surrounding housing  14  and passes through the module housing  6  and the main circuit board  15  and fixes these elements firmly to each other. Due to the metallic form of the pin  16 , it additionally serves the purpose of leading away currents induced in the interior of the module housing  6 . In this connection, it is pointed out that the interior of the module housing  6  is filled with an electrically conductive encapsulating material  30 , in order to provide additional electromagnetic shielding of the optoelectronic module. 
     FIG. 8  shows the module housing of  FIG. 7 , but without the surrounding housing  14  and without the printed circuit board  15 . The terminal contacts  723  of the lower region of the module housing  7  are in this case formed as SMD contacts. 
   Furthermore, the module housing  6  has been completely assembled in the representation of  FIG. 6 . It includes a central part  6   a  and two side parts  6   b ,  6   c , which are fastened with the electrical devices on the central part  6   a  in accordance with the configuration of the circuit board. An exemplary form of hooking between the side parts  6   b ,  6   c  and the central part  6   a  is depicted in  FIG. 8 . The opposing force, which stabilizes the hooking, is provided by the circuit board bent in a U-shaped manner, which is hooked into both side parts  6   b ,  6   c.    
   The outer sides of the side parts  6   b ,  6   c  are provided with small beads  65 , which ensure playfree clamping of the module housing  6  in the surrounding housing  14  represented in  FIG. 7 . 
     FIG. 9  shows, in a rear view, the finished electrooptical module, installed completely in the surrounding housing  14 , with a conducting pin  16  for the mechanical fixing and clamping elements  142  of the surrounding housing for the arresting of the surrounding housing  14  on a main circuit board of the appliance. The CAI module housing  6  is closed by the side parts and accommodates the circuit carrier, bent in a U-shaped manner, with the wiring devices, the transmitting device and the receiving device. An inscription  17  serves for identification and for tracing the production operation. 
     FIG. 10  shows a sectional view of the surrounding housing  14  of  FIGS. 7 and 9 . The surrounding housing  14  has a first region  14   a , which serves for receiving the module housing  6  according to  FIGS. 7 to 9 . A second region  14   b , offset axially with respect to the first region, provides a receiving opening for an optical plug to be coupled on. The two regions are separated from each other by a dividing wall  143 . The dividing wall has in this case an opening  144 , which is aligned in a centered manner with respect to the optical axis  5  and through which the continuation  62  of the module housing  6  fitted into the region  14   a  is inserted, so that the continuation is located with the transducer device, disposed in the continuation, in the region  14   b . Also provided in the region  14   b  is a spring catch  145  for latching engagement with an optical plug and a guiding web  146  for such a plug. 
     FIG. 11  shows, in a view from below, an optical plug that can be coupled with the optoelectronic module of  FIGS. 1 to 10  and for this purpose can be inserted into the surrounding housing  14  of  FIG. 10 . Two fiber ferrules  19 , which receive an optical fiber of a POF cable  20  in each case, have been pressed into a plug housing  181 . The fiber ferrules  19  are optionally fixed in the plug housing  181  by a metal clamp  21 . 
   The fiber ferrules  19  with the POF fibers end in the front region of the plug housing  181  in each case in an opening  182  in the plug housing  181 , into which the continuation  62   a ,  62   b  of the module housing  6  of the optoelectronic transceiver enters during the coupling operation. 
   It is pointed out that the plug housing  181  forms at the extreme end a fixed, peripheral guard wall  181 ′, which projects in a protective manner beyond the end face  221  of the ferrules  19  and/or the POF fibers contained in them and consequently meets the already mentioned kojiri criterion. Due to the fixed guard wall  181 ′, the end faces  221  of the POF fibers are reliably protected from soiling and damage, in particular caused by incorrect plugging or blind plugging. 
     FIG. 12  shows the plug  18  of  FIG. 11 , inserted into the surrounding housing  14  of  FIG. 10 , the module housing  6  having been fitted with the cylindrical continuation  61  into the surrounding housing  14 . The cylindrical continuation  62  protrudes in the way mentioned with respect to  FIG. 10  through the opening  144  of the dividing wall  143  of the surrounding housing  14 . Furthermore, the cylindrical continuation  62  protrudes into the openings  182  of the plug housing  181 , the fiber end face  221  of the POF fibers  20  respectively coming to bear against the fiber stop face  42  (see  FIG. 1 ) of the transducer device. The peripheral guard wall  181 ′ of the plug housing in this case extends beyond the transmitting or receiving devices disposed in the cylindrical continuation  62  and encloses around them to a certain extent. The spring catch  145  of the surrounding housing  14  has engaged in a latching opening of the optical plug  18 , it being possible for unlocking to take place by using a displaceable plug release  23 . 
   It can also be seen that the entire configuration is disposed on a main circuit board  5 , and the surrounding housing  14  is firmly locked with the main circuit board  15  by using the arresting clamps  142  represented in  FIG. 9 . 
     FIG. 13  shows a plan view of the optical plug  18  in the locking region. The spring catch  145  has engaged by using a latching edge  25  on the optical plug  18 . Lateral clamping lobes  24 , which engage in lateral recesses  145   a  of the spring catch  145 , prevent the spring catch from being able to spring out upward. 
     FIG. 14  shows the optical plug in a view from above without the plug release  23  of  FIG. 18  and without the spring catch  145 . Provided in the right-hand region are two spherical elevations  26 , which engage in clearances formed on the underside of the plug release and thereby keep the plug release in a forward position. A kind of spring which allows the elevations  26  to be easily pressed downward when the plug release  23  is pulled back is provided by two elongate clearances  27  respectively provided laterally with respect to the elevations  26 , with the result that the pulling back of the plug release is made easier. 
   It is also represented that the lateral clamping lobes  24  form on their underside oblique edges for the opening of the clamping lobes in interaction with the plug release  23 . An opening  28  in the plug serves for receiving the latching lug of the spring catch  145 . The two optical axes  5 ′,  5 ″ respectively of the transmitting device and of the receiving device are likewise depicted. 
   A triangular elevation  29  serves for the arresting of the plug release  23  and prevents the latter from coming free when the plug is pulled out. 
     FIG. 15  finally shows the plug release  23 . The latter has on its upper side ridges  231 , which facilitate pushing back of the plug release. Formed on the underside are clearances  234 , which, as explained, serve for the fixing and movement by using the half-spheres or elevations  26  according to  FIG. 14 . A rear clearance  235  on the underside of the plug release  23  provides a rearward stop, which prevents the plug release from being pulled out from the optical plug  18 . 
   The front region of the plug release forms two lateral arms  232 ,  233 . The arms respectively have on the one hand an elevation  232   a ,  233   a  with an obliquely running edge  232   a ′,  233 ′ and on the other hand a trapezoidal elevation  232   b ,  233   b . These elevations interact with the clamping lobes  24  in such a way that, when the plug release  23  is pulled back, first of all the oblique edges  232   a ′,  233   a ′ of the elevations  232   a ,  233   a  act on the oblique edges on the underside of the clamping lobes  24 , the clamping lobes as a result spring outward and consequently release the spring catch  145 . Subsequently, the spring catch  145  is raised by the trapezoidal elevations  232   b ,  233   b , with the result that unlocking takes place.