Abstract:
A bi-directional optoelectric transceiver module comprising a bi-directional element with a plate positioned on a side of the bi-directional element wherein the plate is coated with a reflection enhancing coating which reflects light at a first wavelength emitted by a light emitting device and which transmits light emitted by an optical fiber at a second wavelength wherein a light detecting device is positioned to detect at least one of the first and second wavelengths of light.

Description:
CROSS-REFERENCED TO RELATED APPLICATION 
   This application claims the benefit of provisional application No. 60/323,142, filed 13 Sep. 2001. 

   FIELD OF THE INVENTION 
   This invention relates to optical-to-electrical and electrical-to-optical modules and more particularly to bi-directional optics in such modules. 
   BACKGROUND OF THE INVENTION 
   At the present time, transmitting data by optical fibers is very popular. Optical fibers have a large number of advantages over the standard wire transmission devices, including much higher transmission frequencies, less losses, and much higher data rates. Generally, in the present communication systems, each optical fiber has a module that includes a transmission channel and a reception channel at each end. One of the pair of channels receives electrical signals, converts the electrical signals to an optical (light) beam by way of a laser or the like and introduces the beam into one end of the optical fiber, which then transmits the modulated optical beam to a similar module at the other end of the optical fiber. The second channel of the module receives modulated optical beams from the optical fiber, conveys the modulated optical beam to a photo diode or the like, which converts the optical beam back to an electrical signal. A problem with this system is the number of components that must be used at each end of both fibers to receive signals and convert the signals to optical or electrical signals. 
   It would be highly advantageous, therefore, to remedy the foregoing and other deficiencies inherent in the prior art. 
   Accordingly, it is an object of the present invention to provide a new and improved bi-directional optoelectric transceiver module. 
   It is an object of the present invention to provide a new and improved bi-directional optoelectric transceiver module which can receive and transmit optical signals using a single channel. 
   It is another object of the present invention to provide a new and improved bi-directional optoelectric transceiver module which includes fewer components. 
   It is still another object of the present invention to provide a new and improved bi-directional optoelectric transceiver module which is easier to optically align. 
   SUMMARY OF THE INVENTION 
   To achieve the objects and advantages specified above and others, a bi-directional optoelectric transceiver module is disclosed. In a preferred embodiment, the bi-directional optoelectric transceiver module includes a bi-directional element with a plate positioned on a side of the bi-directional element wherein the plate is coated with a reflection enhancing coating which reflects light at a first wavelength and transmits light at a second wavelength. In the preferred embodiment, the bi-directional element and the plate can include glass, plastic, or another suitable optically transparent material which can be molded. 
   In the preferred embodiment, a lens system is positioned to focus light at the first wavelength and a second lens system is positioned to focus light at the second wavelength. In the preferred embodiment, the bi-directional element and the lens systems are formed as a single unit of a molded plastic. 
   The reflection enhancing coating can include silicon oxide (SiO), titanium oxide (TiO), tantalum oxide (TaO), magnesium fluoride (MgF), or another suitable coating material which reflects light at the first wavelength and transmits light at the second wavelength. In the preferred embodiment, the reflection enhancing coating includes a plurality of material layers wherein a thickness of each of the plurality of material layers is chosen so that the reflection enhancing coating reflects light at the first wavelength and transmits light at the second wavelength. 

   
     BRIEF-DESCRIPTION OF THE DRAWINGS 
     Referring to the drawings: 
       FIGS. 1 through 6  are simplified schematic/ray diagrams of six different embodiments of bi-directional optoelectric transceiver modules in accordance with the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring to  FIG. 1 , a simplified schematic/ray diagram is illustrated of an embodiment of a bi-directional optoelectric transceiver module  10  in accordance with the present invention. The transceiver of module  10  includes a device  11 , which may be a laser or other device that converts electrical signals to optical signals in a well-known manner. The transceiver of module  10  also includes a photodetector device  12 , which may be a photodiode or other device that converts optical signals to electrical signals. For convenience and simplicity of understanding, devices for converting electrical signals to optical signals will be referred to generally as lasers and devices for converting optical signals to electrical signals will be referred to generally as photodetectors throughout this disclosure with the understanding that any other device that performs the same function can be substituted. 
   In this disclosure, laser  11  generates light at a wavelength λ 1  along an optical axis  7  and photodetector  12  receives light at a wavelength λ 2  along an optical axis  8 . As will be understood after a careful study of the detailed description below, the specific wavelengths of λ 1  and λ 2  are selected in accordance with various materials utilized in module  10  to enhance the reflection and/or transmission of the light between laser  11  and the optical fiber or to enhance the reflection and/or transmission of the light between the optical fiber and photodetector  12 . In one specific example, λ 1  and λ 2  are 850 nm and 1310 nm, or vice versa. It should also be understood that through the use of different materials the positions of laser  11  and photodetector  12 , as described in detail below, could be reversed. 
   The beam of light generated by laser  11  is focused by a lens system, including one or more lenses (illustrated as a single lens  14 ), onto a bi-directional element  15 . Element  15  is a prism formed of material, such as glass, plastic, etc., that is transparent to light generated by laser  11  (light at wavelength λ 1 ) and light received by photodetector  12  (light at wavelength λ 2 ). The prism has a triangular cross-section with a side  16  positioned generally perpendicular to the light beam generated by laser  11 , a side  18  generally perpendicular to side  16 , and a side  20  oriented at an angle (in this embodiment 45°) to the light beam generated by laser  11 . In the preferred embodiment, optical axes  7  and  8  intersect at approximately side  20 . Thus, light from laser  11  enters side  16  of the prism with a minimum of reflection and is reflected by side  20  approximately 90° out through side  18 . 
   Side  20  has a coating  22  of multiple layers of material that is selected and designed to enhance the reflection of light at wavelength λ 1 . Thus, substantially all of the light generated by laser  11  is reflected by side  20  and coating  22  out through side  18  along optical axis  8 . The reflected light emanating from side  18  is focused by a lens system, including one or more lenses (illustrated as a single lens  24 ), through an optional anti-reflection glass plate  25  onto the glass core  26  of an optical fiber  28 . Glass plate  25  is positioned in abutting engagement with the end of optical fiber  28  to reduce reflections from the end of core  26  and to provide a better coefficient match between core  26  and the material between lens  24  and core  26  (generally air). 
   Light at wavelength λ 2  conducted by optical fiber  28  from an external source is focused by lens  24  through side  18  onto side  20  of element  15  along axis  8 . Coating  22  on side  20  of element  15  is selected and designed to enhance the transmission (non-reflection) of light at wavelength λ 2  out through side  20 . The light passing out of side  20  of element  15  is focused by a lens system, including one or more lenses (illustrated as a single lens  32 ), along axis  8  and onto photodetector  12 . Thus, substantially all of the light from optical fiber  28  entering element  15  is transmitted through side  20  and coating  22  to photodetector  12 . As stated generally above, wavelengths λ 1  and λ 2  and coating  22  are selected to provide maximum reflection and transmission, respectively of the generated or received light. It will be understood that because of the difference in wavelengths for transmission and reception and the separation performed by element  15 , these functions can be performed simultaneously with little or no interference. Any leakage of light that may occur can be removed by electrical and/or optical filtering, if deemed beneficial. Also, wavelengths λ 1  and λ 2  and coating  22  can be selected to reverse the positions of laser  11  and photodetector  12  if desired. 
   In a specific example, coating  22 , or any of the subsequently discussed coatings performing the same functions, includes a layer or layers of material that form a mirror for one of the frequencies and directly transmits the other frequency. Typical examples of materials that perform this function are: silicon oxide (SiO); titanium oxide (TiO); tantalum oxide (TaO); magnesium fluoride (MgF); and combinations of these materials or similar materials. Here it will be understood by those skilled in the art that the number of layers, the thickness of the layers and the index of refraction of the material can be utilized to produce a mirror for one wavelength and a direct passage for another wavelength. Typical examples of mirrors formed from dielectrics and from semiconductor materials can be found in the laser art. 
   In a slightly different embodiment, some small amount of light from laser  11  can be allowed to pass through element  15  to photodetector  12 . In addition to the normal communication (receiver) channel incorporating photodetector  12 , photodetector  12  is connected into a circuit that is used to monitor and control the output of laser  11 . In its simplest form the receiver channel circuitry and the monitor and control circuitry can be switched so as to alternatively connect photodetector  12  into one or the other of the circuits. In this form transmission or reception by module  10  would be performed separately. In a slightly more complicated form, electrical signals produced by light at wavelength λ 1  are filtered from electrical signals produced by light at wavelength λ 2 , with the electrical signals produced by light at wavelength λ 1  being used to monitor and control the output of laser  11 . 
   Turning now to  FIG. 2 , a simplified schematic/ray diagram is illustrated of another embodiment of a bi-directional optoelectric transceiver module  100  in accordance with the present invention. Components in module  100  which are similar to components in module  10  of  FIG. 1  are designated with similar numbers having a 1 added to indicate the different embodiment. Also, the above description of the various components in  FIG. 1  applies equally to similar components in FIG.  2 . 
   In module  100 , element  115  is preferably formed from molded plastic and includes a lens  114 , which focuses light generated by laser  111  at wavelength λ 1  along an optical axis  107  and onto a side  120  that performs the same function as side  20  in FIG.  1 . In the preferred embodiment, a reflection enhancing coating  122  of multiple layers of material is applied to side  120  to direct substantially all light generated by laser ill at wavelength λ 1  out through a lens  124  along an optical axis  108 . However, it will be understood that coating  122  can be positioned proximate to side  120  using other means, such as applying coating  122  to a plate wherein the plate is positioned adjacent to side  120 . Lens  124  focuses light reflected by side  120  and coating  122  from element  115  onto glass plate  125  and thence into optical fiber  128 . By molding lenses  114  and  124  into the body of element  115 , a substantial saving in components and assembly can be realized, since mounting and alignment of the lenses are eliminated. 
   Light at wavelength λ 2 , conducted by optical fiber  128  from an external source, is focused by lens  124  onto side  120  of element  115 . Coating  122  on side  120  of element  115  is further selected to enhance the transmission of light at wavelength λ 2  out through side  120  along axis  108 . The light passing through side  120  of element  115  is prefocused by lens  124  onto photodetector  112 . Here it will be noted that lens  124  is positioned to perform two different focusing functions. It should also be noted that lens  24  in  FIG. 1  can be used in a similar fashion (thereby eliminating lens  32 ) or an additional lens can be incorporated into module  100 , if desired. Thus, substantially all of the light from optical fiber  128  entering element  115  is transmitted through side  120  and coating  122  to photodetector  112 . It should be understood that coating  122  can be applied to side  120  in any convenient sequence. 
   Turning now to  FIG. 3 , a simplified schematic/ray diagram is illustrated of another embodiment of a bi-directional optoelectric transceiver module  200  in accordance with the present invention. Components in module  200  which are similar to components in module  10  of  FIG. 1  are designated with similar numbers having a 2 added to indicate the different embodiment. Also, the above description of the various components in  FIG. 1  applies equally to similar components in FIG.  3 . 
   In module  200 , element  215  is preferably formed from molded plastic and includes a lens  214 , which focuses light generated by laser  211  at wavelength λ 1  along an optical axis  207  and onto a side  220  that performs the same function as side  20  in FIG.  1 . In the preferred embodiment, a reflection enhancing coating  222  including multiple layers of material is applied to side  220  to reflect substantially all light generated by laser  211  at wavelength λ 1  toward optical fiber  228  along optical axis  208 . Light reflected by side  220  is prefocused by lens  214  onto plate  225  and thence into core  226  of optical fiber  228 , in this preferred embodiment, but additional lenses can be incorporated if desired. Also, lens  214  is formed as a projection spaced from side  220  and presenting a rear surface  235  to plate  220 . Surface  235  is curved to direct back-reflected light (i.e. light which would be reflected back into laser  211 ) away from laser  211  so as to reduce or eliminate this back-reflected light. 
   Light at wavelength λ 2 , conducted by optical fiber  228  from an external source, impinges directly onto side  220  of element  215 . Coating  222  on side  220  of element  215  is selected to enhance the transmission of light at wavelength λ 2  through side  220  along optical axis  208  and into element  215 . The light passing through side  220  into element  215  is focused by lens  224  onto photodetector  212 . It should be noted that lens  32  in  FIG. 1  can be used in a similar fashion (thereby eliminating lens  24 ) or an additional lens can be incorporated into module  200 , if desired. Thus, substantially all of the light from optical fiber  228  entering element  215  is transmitted through side  220  and coating  222  to photodetector  212 . It should be understood that coating  222  can be applied to side  220  in any convenient sequence. By molding lenses  214  and  224  into the body of element  215 , a substantial saving in components and assembly can be realized, since mounting and alignment of individual lenses are eliminated. 
   Turning now to  FIG. 4 , a simplified schematic/ray diagram is illustrated of another embodiment of a bi-directional optoelectric transceiver module  300  in accordance with the present invention. Components in module  300  which are similar to components in module  10  of  FIG. 1  are designated with similar numbers having a 3 added to indicate the different embodiment. Also, the above description of the various components in  FIG. 1  applies equally to similar components in FIG.  4 . 
   In module  300 , element  315  is preferably formed from molded plastic and includes a lens  314 , which focuses light generated by laser  311  at wavelength λ 1  along an optical axis  307  and onto a side  320  that performs the same function as side  20  in FIG.  1 . Side  320  is preferably glass but could be a plastic or any other material which is capable of performing the described functions and which can be easily and conveniently incorporated into molded element  315 . A reflection enhancing coating  322  including multiple layers of material is applied to side  320  to reflect substantially all light generated by laser  311  at wavelength λ 1  toward optical fiber  328 . Light reflected by side  320  is focused by lens  324  onto core  326  of optical fiber  328  along an optical axis  308 , in this preferred embodiment, but additional lenses can be incorporated if desired. 
   Light at wavelength λ 2 , conducted by optical fiber  328  from an external source, impinges directly onto side  320  of element  315  along axis  308 . Coating  322  on side  320  of element  315  is further selected to enhance the transmission of light at wavelength λ 2  through side  320 . The light passing through element  315 , including side  320 , is prefocused by lens  324  onto photodetector  312  along axis  308 . It should be noted that lens  24  in  FIG. 1  can be used in a similar fashion (thereby eliminating lens  32 ) or an additional lens can be incorporated into module  300 , if desired. Thus, substantially all of the light from optical fiber  328  entering element  315  is transmitted through side  320  and coating  322  to photodetector  312 . It should be understood that coating  322  can be applied to side  320  in any convenient sequence. By molding lenses  314  and  324  into the body of element  315 , a substantial saving in components and assembly can be realized, since mounting and alignment of the lenses are eliminated. 
   Turning now to  FIG. 5 , a simplified schematic/ray diagram is illustrated of another embodiment of a bi-directional optoelectric transceiver module  400  in accordance with the present invention. In this disclosure, a laser  411  generates light at a wavelength λ 1  along an optical axis  407  and a photodetector  412  receives light at a wavelength λ 2  along an optical axis  409 . The beam of light generated by laser  411  is focused by a lens system, including one or more lenses (illustrated as a single glass ball  414 ), onto an angled surface  415 . In this embodiment glass ball  414 , surface  415 , photodetector  412 , and laser  411  are, or optionally can be, mounted on a common substrate  416 , such as a silicon substrate on which some or all of the components are formed and/or mounted using common semiconductor fabrication processes. 
   Glass ball  414  is spherical and constructed with a diameter such that it operates like an optical lens with the desired characteristics. In this embodiment, glass ball  414  is mounted in a depression or cavity  417  in substrate  416 , by means of an adhesive or the like. Cavity  417  can be accurately machined, using standard semiconductor techniques, to eliminate any alignment problems. Light from laser  411  is focused by glass ball  414  onto angled surface  415 , which reflects the light at approximately 90° onto a surface  418  of an element  420 . 
   Element  420  is formed of material, such as glass, plastic, etc., that is transparent to light generated by laser  411  (light at wavelength λ 1 ) and light received by photodetector  412  (light at wavelength λ 2 ). Surface  418  has a coating  422  including multiple layers of material which is selected to enhance the transmission of light at wavelength λ 1  along an optical axis  408  through surface  418  and element  420 . The light passing through element  420  and coating  422  is focused by a lens  424 , integrally molded into element  420 , through a glass plate  425  onto glass core  426  of an optical fiber  428 . Glass plate  425  is positioned in abutting engagement with the end of optical fiber  428  to reduce reflections from the end of core  426  and to provide a better coefficient match between core  426  and the material between lens  424  and core  426  (generally air). Thus, substantially all of the light generated by laser  411  is transmitted by coating  422  and element  420  to optical fiber  428  along optical axis  408 . 
   Light at wavelength λ 2  conducted by optical fiber  428  from an external source is focused by lens  424  onto surface  418  of element  420  along axis  408 . Coating  422  on surface  418  of element  420  is further selected to enhance the reflection of light at wavelength λ 2  within element  420 . The light reflected within element  420  is reflected a second time by a surface  432  of element  420  along an optical axis  406 . Surface  432  also has a coating  434  which is selected to enhance the reflection of light at wavelength λ 2  within element  420 . Light reflected by surface  432  is focused by a lens  436  along axis  409 , formed integrally in element  420 , onto photodetector  412 , mounted on substrate  416 . Thus, substantially all of the light from optical fiber  428  entering element  420  is reflected by surfaces  418  and  432  to photodetector  412 . As stated generally above, wavelengths λ 1  and λ 2  and coatings  422  and  434  are selected to provide maximum transmission and reflection, respectively, of the generated or received light. 
   By molding lenses  424  and  436  into the body of element  420 , a substantial saving in components and assembly can be realized, since mounting and alignment of the lenses are eliminated. It will be understood that because of the difference in wavelengths for transmission and reception and the separation performed by element  420 , these functions can be performed simultaneously with little or no interference. Any leakage of light that may occur can be removed by electrical and/or optical filtering, if deemed beneficial. Also, wavelengths λ 1  and λ 2  and coatings  422  and  434  can be selected to reverse the positions of laser  411  and photodetector  412  if desired. 
   Also in this embodiment, some small amount of light from laser  411  can be allowed to pass through element  420  to photodetector  412 . In addition to the normal communication (receiver) channel incorporating photodetector  412 , photodetector  412  is connected into a circuit that is used to monitor and control the output of laser  411 . In its simplest form the receiver channel circuitry and the monitor and control circuitry can be switched so as to alternatively connect photodetector  412  into one or the other of the circuits. In this form transmission or reception by module  400  would be performed separately. In a slightly more complicated form, electrical signals produced by light at wavelength λ 1  are filtered from electrical signals produced by light at wavelength λ 2 , with the electrical signals produced by light at wavelength λ 1  being used to monitor and control the output of laser  411 . 
   Turning now to  FIG. 6 , a simplified schematic/ray diagram is illustrated of another embodiment of a bi-directional optoelectric transceiver module  500  in accordance with the present invention. In this disclosure, a laser  511  generates light at a wavelength λ 1  and a photodetector  512  receives light at a wavelength λ 2 . The beam of light generated by laser  511  is focused by a lens system, including one or more lenses (illustrated as a single glass ball  514 ), onto an angled surface  515 . In this embodiment glass ball  514 , surface  515 , photodetector  512 , and laser  511  are, or optionally can be, mounted on a common substrate  516 , such as a silicon substrate on which some or all of the components are formed and/or mounted using common semiconductor fabrication processes. 
   Glass ball  514  is circular and constructed with a diameter such that it operates like an optical lens with the desired characteristics. In this embodiment, glass ball  514  is mounted in a depression or cavity  517  in substrate  516 , by means of an adhesive or the like. Cavity  517  can be accurately machined, using standard semiconductor techniques, to eliminate any alignment problems. Light from laser  511  is focused by glass ball  514  onto angled surface  515 , which reflects the light at approximately 90° onto a surface  518  of an element  520 . 
   In this embodiment element  520  is a four-sided parallelepiped formed of material, such as glass, plastic, etc., that is transparent to light generated by laser  511  (light at wavelength λ 1 ) and light received by photodetector  512  (light at wavelength λ 2 ) Surface  518  has a coating  522  which is selected to enhance the transmission of light at wavelength λ 1  through surface  518  and element  520  and out an upper end  523 . The light passing through element  520  and coating  522  is focused by a lens  524  through a glass plate  525  onto the glass core  526  of an optical fiber  528 . Glass plate  525  is positioned in abutting engagement with the end of optical fiber  528  to reduce reflections from the end of core  526  and to provide a better coefficient match between core  526  and the material between lens  524  and core  526  (generally air). Here it should be noted that lens  524  can be any commercially available “off-the-shelf” lens, either plastic or glass. Thus, substantially all of the light generated by laser  511  is transmitted by coating  522  and element  520  to optical fiber  528 . 
   Light at wavelength λ 2  conducted by optical fiber  528  from an external source is focused by lens  524  through upper end  523  and onto surface  518  of element  520 . Coating  522  on surface  518  of element  520  is further selected to enhance the reflection of light at wavelength λ 2  within element  520 . The light reflected within element  520  is reflected a second time by a surface  532  of element  520 . Surface  532  also has a coating  534  which is selected to enhance the reflection of light at wavelength λ 2  within element  520 . Light reflected by surfaces  518  and  532  is prefocused by lens  524  out through a lower end  535  of element  520  onto photodetector  512 , mounted on substrate  516 . Thus, substantially all of the light from optical fiber  528  entering element  520  is reflected by surfaces  518  and  532  to photodetector  512 . As stated generally above, wavelengths λ 1  and λ 2  and coatings  522  and  534  are selected to provide maximum transmission and reflection, respectively of the generated or received light. It will be understood that because of the difference in wavelengths for transmission and reception and the separation performed by element  520 , these functions can be performed simultaneously with little or no interference. Any leakage of light that may occur can be removed by electrical and/or optical filtering, if deemed beneficial. Also, wavelengths λ 1  and λ 2  and coatings  522  and  534  can be selected to reverse the positions of laser  511  and photodetector  512  if desired and can be provided as multiple layers on either or both sides of the supporting plates. 
   Also in this embodiment, some small amount of light from laser  511  can be allowed to pass through element  520  to photodetector  512 . In addition to the normal communication (receiver) channel incorporating photodetector  512 , photodetector  512  is connected into a circuit that is used to monitor and control the output of laser  511 . As understood by those skilled in the semiconductor art, both circuits can be integrated onto a common chip with photodetector  512 , if desired. In its simplest form the receiver channel circuitry and the monitor and control circuitry can be switched so as to alternatively connect photodetector  512  into one or the other of the circuits. In this form transmission or reception by module  500  would be performed separately. In a slightly more complicated form, electrical signals produced by light at wavelength λ 1  are filtered from electrical signals produced by light at wavelength λ 2 , with the electrical signals produced by light at wavelength λ 1  being used to monitor and control the output of laser  511 . 
   It will be understood that any or all of the various components and embodiments discussed above can be incorporated into any of the various embodiments. Also, any specific components or materials described can generally be replaced with equivalent components or materials capable of performing the described functions. 
   Various changes and modifications to the embodiments herein chosen for purposes of illustration will readily occur to those skilled in the art. To the extent that such modifications and variations do not depart from the spirit of the invention, they are intended to be included within the scope thereof which is assessed only by a fair interpretation of the following claims.