Abstract:
A multi-channel optical connector that includes a multi channel optical fiber block including at least one optical fiber capable of being optically coupled to at least one optical device. The multi-channel optical fiber block is incorporated in a plastic molding that is complimentary in shape to that of an optical device array block, and thus can be plugged into the optical device array block. The close tolerances maintained in manufacturing of the connector results in accurate alignment of the fibers captured in the multi-channel optical fiber block with the optical devices in the optical device array block. The close tolerances can be achieved by using MEMS (Micro Electro Mechanical System) processing techniques to manufacture the V-grooves in a silicon V-block, which is part of the multi-channel optical fiber block. Alternatively, V-grooves can be produced in the multi-channel optical fiber block by plastic molding. The connector includes a housing that surrounds the connector core and the buffered fiber that is outside the cable jacket to providing protection and strain relief for the fibers.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application relates to and incorporates by reference in its entirety the commonly-assigned copending U.S. patent application entitled “Multichannel Optical Transmitter/Receiver Module and Manufacturing Method Thereof” Ser. No. 09/608,207, filed Jun. 30, 2000. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a multi-channel optical connector and, more particularly, to a rugged-type multi-channel optical connector for use with optical transmitter modules and optical receiver modules. 
     2. Description of the Related Art 
     Recently, communication systems designers are vigorously adapting their designs for the use of optical fiber technology in various communication fields. Optical communication systems enable use of high frequency signals and suffer less signal loss than conductor based technologies and are therefore better suited for the high bandwidth communications that are increasingly in demand. Optical communication systems are suitable to use in high speed-long distance transmission systems. 
     During optical transmission of data, one channel of serial data is generally utilized for transmitting parallel data on N channels. In this case, the transmission speed of the serial data should be at least N times faster than each of the parallel data channels. High speed transmission circuits require expensive equipment; therefore, multiple transmission channels are often utilized to reduce the burden of a high speed transmitting circuit. In order to use multiple optical channels, a plurality of optical transmission systems, each including a light source, an optical fiber, and light detector, are required. For multi-channel optical transmitter/receiver modules, an accurate alignment of optical fibers with sources and detector is required not only for each channel but also for adjacent channels. Therefore, multi-channel optical transmitter/receiver modules need an optical connector which is highly accurate and, consequently, is more complicated than that of a single channel optical transmitter/receiver module. 
     FIG. 1 is an exemplary schematic diagram illustrating an active alignment method for a multi channel optical connector  101  and laser diodes  100 . In order to arrange laser diodes  100 , for example, with respect to optical fibers  110 , laser diodes  100  are first fixed so that they are separated by regular, usually uniform, intervals. Next, optical fibers  110  are fixed on a block  120  having grooves with the same regular intervals with which the laser diodes have been fixed. Then, laser diodes  100  and optical fibers  110  are aligned by moving block  120  with respect to laser diodes  100 . Block  120  can be moveable in all three directions. An optimal alignment between optical fibers  110  and laser diodes  100  can be achieved by monitoring the optical output power from each optical fiber of optical fibers  110  while moving block  120 . When the output power from each of the optical fibers  110  is maximized, block  120  can be fixed relative to diodes  100 . This method is referred to as the active alignment method because the maximum output power is sought by monitoring the optical output power from fibers  110 . The active alignment method can approach the optimum arrangement, however it requires expensive equipment and a lot of labor hours to accomplish. Further, the active alignment method does not lend itself to systems where plugable connectors are desirable. 
     FIG. 2 is an exemplary schematic diagram illustrating a passive alignment method for a multi channel optical connector  201  and optical devices  200 . In contrast to the active alignment method illustrated in FIG. 1, the passive alignment method does not include monitoring optical output power. Multi channel optical connector  201  includes an optical device array block  210  with optical devices  200 , each electrically coupled to one of electrical conductors  211 , arranged to have regular, uniform, intervals. Multi channel optical connector  201  also includes a multi channel optical fiber block  220  having optical fibers  221  arranged with the same regular intervals as that of optical devices  200  of optical device array block  210 . Optical device array block  210  can be fixed on a substrate (not shown) by soldering. Multi channel optical fiber block  220  can be plugable. Optical fibers  221  are then aligned with optical devices  200  when multi channel optical fiber block  220  is plugged into optical device array block  210 . Optical devices  200  can be laser diodes or photodiodes. Even though the passive alignment method is not optimized as with the active alignment method, it has the advantage of being faster (requiring fewer labor hours), requires less expensive equipment, and therefore is less expensive to perform. 
     FIG. 3 illustrates a conventional method of assembling connector  201  of FIG.  2 . Typically, an optical transmitter/receiver module will include two connectors such as connector  201  of FIG. 2, arranged such that light sources in one module are coupled with light detectors in the other module via optical fibers. Optical fibers  320  are inserted in grooves  311  on a connector block  310 . Optical fibers  320  can be multi mode or single mode optical fibers. Grooves  311  guide optical fibers  320  into holes  322 , typical 250 μm diameter holes, in connector block  310 . Grooves  311  have uniform intervals between any two adjacent grooves  311 . Optical fibers  320  are fixed in place by a cover  300 , which can also be grooved with grooves  312  having the same uniform intervals as connector block  310 . Connector block  310  is usually made from a plastic material for ease of manufacturing and lowered cost. End facets  321  of optical fibers  320  are usually smoothly polished in order to facilitate the coupling of light into and out of optical fibers  320 . 
     TABLE 1 shows the result of a calculation for an allowable tolerance of the alignment depending on the various diameters of optical fibers and a coupling efficiency between the optical fiber and the optical devices. The calculations in TABLE 1 are based on several parameters. The allowable tolerance for alignment between a laser diode and an optical fiber is based on the requirement that more than about 90% of the maximum optical output of the laser diode be coupled into the optical fiber. The allowable tolerance of alignment between an optical fiber and a photo diode is based on the requirement that more than about 90% of the maximum light output from the optical fiber be coupled into the photo diode. The divergence angle of the laser diode beam is assumed to be about 15°. The diameter of the light receiving aperture of the photodiode is assumed to be about 200 μm. Additionally, the laser diode is separated by about 450 μm from the optical fiber. 
     
       
         
               
               
               
               
               
               
             
               
               
               
               
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                   
                 Laser diode - 
                 Optical fiber - 
                 Laser diode - 
                 Optical fiber - 
                   
               
               
                 Optical fiber 
                 Optical fiber Allowable 
                 Photo diode Allowable 
                 Optical fiber Maximum 
                 Photo diode Maximum 
                 Total maximum 
               
               
                 core diameter 
                 tolerance of alignment 
                 tolerance of alignment 
                 coupling efficiency 
                 coupling efficiency 
                 Coupling efficiency 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 0.5 
                 mm 
                 ±140 μm  
                 ±90 μm 
                 100%  
                 21% 
                 21% 
               
               
                 0.25 
                 mm 
                 ±40 μm 
                 ±45 μm 
                 90% 
                 67% 
                 60% 
               
               
                 0.0625 
                 mm 
                 ±20 μm 
                 ±65 μm 
                 16% 
                 100%  
                 16% 
               
               
                   
               
             
          
         
       
     
     If a 0.5 mm core diameter plastic optical fiber is used, it would be possible to manufacture a connector having approximately 100 μm of allowable tolerance of alignment between the optical fiber and the laser diode by plastic molding. However, only 21% of the light output from the optical fiber can be coupled into the photodiode. Alternatively, if a 0.25 mm core diameter plastic optical fiber is used, 67% of the light output from the optical fiber can be coupled to the photodiode. The decreased diameter of the optical fiber can bring three times the signal to the photo diode without increasing the output of the laser diode; however, the allowable tolerance of alignment between the optical fiber and the laser diode would be reduced by an amount 0.29 that of the 0.5 mm diameter plastic optical fiber. It is very difficult to manufacture such a connector and satisfy the allowable tolerances with plastic molding. The passive alignment method is generally accomplished with plastic optical fiber having relatively large diameters, generally about 0.51˜1.0 mm, for proper transmission of the optical signal. 
     If a 0.0625 mm diameter multi mode silica optical fiber is used, it is extremely difficult to satisfactorily manufacture the connector with the required reduced alignment tolerances by plastic molding. However, even though the amount of the output of the laser diode actually coupled into the multi mode silica optical fiber is small, all of the light coming out from the optical fiber can be coupled into the photodiode. Thus, the maximum output of the photodiode is almost the same as that of the 0.5 mm diameter optical fiber. The silica optical fiber is essential, however, for high speed-long distance signal transmission because silica optical fiber has almost no loss of power and a high cut-off frequency compared with plastic optical fiber. One drawback of using multi mode silica fiber is the small allowable tolerance in the alignment of fiber core with the laser diode. If the tolerance is exceeded the coupling efficiency will decrease, thereby increasing the loss in signal power. 
     FIG. 3A shows a typical optical fiber prepared for insertion into grooves  311  of connector block  310  (FIG.  3 ). Optical fiber  320  is a buffered optical fiber having a buffer  340 . Buffer  340 , for example, can be a 900 μm diameter buffer. Buffer  340  is stripped away to expose buffer  341 . Buffer  341 , for example, can be a 250 μm diameter buffer. Buffer  341  is inserted into one of holes  322  in connector block  310  and is guided by grooves  311 . The center of buffer  341 , however, may not be aligned with the center of fiber core  343 , even though holes  321  have uniform intervals. Therefore, the centers of fiber core  343  may be arranged with non-uniform intervals. 
     However, the center of fiber core  343  is well aligned with the center of bare fiber  342 , which may be a 125 μm diameter fiber. If bare fiber  342  were placed into grooves  311  instead of buffer  341 , the center of core  343  can be aligned accurately. However, it is difficult to make small diameter holes and grooves (125 μm diameters, for example) using plastic injection molding since a very small and long needle-shaped molding core, which can be easily broken, is needed. Additionally, since the small diameter buffer  341  is fixed in connector block  310  while the large diameter buffer  340  is not, stress is induced at the junction between buffer  340  and buffer  341 . 
     FIG. 3B shows a conventional assembly of a plurality of buffered fibers  330 , which can be 900 μm buffered fibers, and a conventional connector  332 . Buffered fibers  330  are not enclosed in a cable sheath, and therefore are susceptible to breakage or excessive bending that can result in increased loss of power for the optical signal. Connector  332  mates with device module  334  thereby aligning the optical fibers  330  with light sources or light detectors present in the device module  334 . Conventional connector  332  does not provide any strain relief mechanism, therefore any movement of connector  332  or even fibers  330  can potentially degrade the signal transmission characteristics at the interface of optical fibers  330  and the light source or the detector. 
     Therefore, there is need for a multi-channel optical connector capable of being precisely aligned in a fast, cost sensitive fashion to yield low loss connections especially for multimode fiber with 62.5 or 50 μm diameter. It is also desirable to use rugged cable to avoid the breakage of fibers or the excessive bending of fibers resulting in higher loss of power for the optical signal. It is also desirable to provide a strain relief to avoid variation in transmission characteristics due to forces acting on the fibers or the connector body. 
     BRIEF SUMMARY OF THE INVENTION 
     In accordance with the present invention, a multi-channel optical connector is disclosed that enables accurate alignment of optical fibers and optical devices, can have a rugged connector design that includes strain relief, and at the same time can support transmission of high frequency signals without interference or noise. 
     In one embodiment, the multi-channel optical connector includes a V-groove block, which can be made from silicon or plastic, and large holes for receiving at least one optical fiber so that at least one optical fiber is optically coupled to at least one optical device of a device array block. The multi channel optical connector is incorporated in a plastic molding that is complimentary in shape to the device array block, and thus can be plugged into the device array block. 
     In some embodiments, close tolerances are maintained in manufacturing of the multi-channel optical connector and the device array block, which results in accurate alignment of the fibers captured in the multi-channel optical connector with the optical devices in the device array block. The close tolerances can be achieved by using MEMS (Micro Electro Mechanical System) processing techniques. The bare fiber can be placed on V-grooves in the V-groove block. 
     The V-groove block can be made from silicon or plastic and is integrally fixed in the multi-channel optical fiber block. A buffered fiber is affixed in the multi-channel optical fiber block through holes in the multi-channel optical fiber block. The multi-channel optical fiber block also includes a trench structure between the holes and the V-grooves of the V-block so that bare fiber (e.g., 125 μm diameter) can be placed in the V-grooves while a large diameter buffer (e.g., 900 μm) is placed through the holes while reducing the stress between the buffered and unbuffered portions of the optical fibers. 
     The connector can also include a stopper and a housing. The stopper is fixedly attached to the sheath of a cable from which at least one of the optical fiber captured in the connector core is derived. The stopper is captured in the housing when the connector is plugged into the device module. The capturing of the stopper in the housing prevents the cable from translating or rotating and provides strain relief for the at least one optical fiber. Cable holding buttons in their locked position aid the stopper in preventing motion of the cable. 
     The connector is suitable for use with a cable that has a jacket enclosing buffered fibers. The buffer can be captured in the multi-channel optical connector; thus, bare fiber is not exposed to the elements, enhancing the structural ruggedness of the conductor. Additionally the housing surrounds the multi-channel optical connector and the jacketed fiber that is outside the buffer providing further protection and strain relief. 
     These and other embodiments of the invention are further discussed below with reference to the following figures. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows an exemplary schematic diagram illustrating an active alignment method for a multi channel optical connector. 
     FIG. 2 shows an exemplary schematic diagram illustrating a passive alignment method for a multi channel optical transmitter. 
     FIG. 3 shows an assembly diagram of a conventional method of implementing the passive alignment method for the multi-channel optical fiber block. 
     FIG. 3A shows a buffered optical fiber. 
     FIG. 3B shows a conventional connector assembly having buffered fibers. 
     FIG. 4 shows a schematic block diagram of an optical transmitter/receiver system having an optical transmitter/receiver module according to the present inventions. 
     FIG. 5 shows the variation of the output power from an optical fiber depending on the misalignment between the beam from a laser diode and the center of the cross-section of an optical fiber. 
     FIG. 6A shows an optical connector in accordance with the present invention just prior to insertion into the optical transmitter module or the optical receiver module. 
     FIG. 6B shows the optical connector of FIG. 6A installed on an optical transmitter module or optical receiver module. 
     FIG. 6C shows a cross section of an exemplary fiber cable. 
     FIGS. 6D and 6E show an embodiment of placement of a stopper on a fiber cable such as the fiber cable shown in FIG.  6 C. 
     FIGS. 6F,  6 G, and  6 H show an embodiment of an optical connector assembled on a panel mount. 
     FIG. 7A is a plan view of the multi channel optical fiber block used in the optical connector of FIG.  6 A and FIG.  6 B. 
     FIG. 7B is an elevation view of the multi-channel optical fiber block used in the optical connector of FIG.  6 A and FIG.  6 B. 
     FIG. 7C is a side view of the multi-channel optical fiber block used in the optical connector of FIG.  6 A and FIG.  6 B. 
     FIGS. 7D,  7 E and  7 F are a plan view, an elevation, and a side view, respectively, of a second embodiment of a multi-channel optical fiber block according to the present invention. 
     FIGS. 7G,  7 H, and  71  are a plan view, an elevation, and a side view, respectively, of an example of a cover for a multi-channel optical fiber block. 
     FIG. 8A shows a side view of an assembly of a fiber in a multi-channel optical fiber block without a trench. 
     FIG. 8B shows a side view of an assembly of a fiber in a multi-channel optical fiber block having a trench. 
     FIG. 9 shows a method of capturing fiber in a multi-channel optical fiber block. 
     FIG. 10 shows an assembled multi-channel optical fiber block according to the present invention. 
    
    
     In the figures, elements having the same designation in the various figures have the same or similar function. 
     DETAILED DESCRIPTION 
     FIG. 4 illustrates a schematic block diagram of an optical transmitter and receiver system  90  having a multichannel optical transmitter/receiver module  80 . Module  80  includes a device module  61   a  having a light source  60   a , a device module  61   b  having a detector  60   b , a fiber optic cable having an optical fiber  70  and connectors  50   a  and  50   b , one at each end of the fiber optic cable. Each module  61   a  and  61   b  can be a transmitter/receiver module and can both transmit and receive optical signals. In FIG. 4, data is transmitted from a parallel data bus  10   a  at point A to a parallel data bus  10   b  at point B through multichannel optical transmitter/receiver module  80 . Parallel data from parallel data bus  10   a  at point A is transformed to serial data for transmission by parallel/serial converting circuit  20   a . The serial data is then input to a laser driving circuit  30 , which transforms electrical signals representing the serial data to optical signals by appropriately driving a light source  60   a  in optical device module  61   a . The optical signal is transmitted to a detector  60   b  in optical device module  61   b  at a receiving site near point B through connectors  50   a  and  50   b  and optical fiber  70 . Detector  60   b  generates electrical signals based on the transmitted optical signals. Because the electrical signals coming from photodiode  60   b  may be weak, the electrical signals can be amplified and restored to digital format to recover the originally transmitted electrical signals by an amplifier/signal recovery circuit  40 . The recovered electrical signals are then converted back to parallel data format by a serial/parallel converting circuit  20   b  and coupled to parallel data bus  10   b  at point B. The transmission of data from point A to point B is, then, accomplished by transmitting serial data through optical fiber  70 . In general, optical transmitter and receiver system  90  can transmit either parallel formatted data or serially formatted data from point A to point B. Optical device module  61   a  can have more than one light source  60   a  and may include detectors; optical device module  61   b  can have more than one photodiode  60   b ; and connector  50   a  and  50   b  can receive more than one fiber  70 . 
     Optical transmitter/receiver module  80  converts the electrical signals representing serial data to an optical signal, transmits the optical signal over a distance, and converts the optical signal to electrical signals representing the serial data. As shown in FIG. 4, optical transmitter/receiver module  80  includes a light source  60   a  for converting the electrical signal to light, an optical fiber  70  for transmitting the light and a light detector  60   b  for reconverting the transmitted light to electrical signals. An optical connector  50   a  couples light from light source  60   a  into optical fiber  70  and another optical connector  50   b  couples light from optical fiber  70  into light detector  60   b . Light source  60   a  must be accurately arranged with respect to optical fiber  70  in order to optimize the coupling of light into optical fiber  70 . Optical fiber  70  must also be accurately arranged with respect to light detector  60   b  in order to optimize the coupling of light from optical fiber  70  into detector  60   b . The transfer of optical signals between source  60   a  and detector  60   b , then, should be optimized to reduce the signal power loss and enable restoration of the serial data electrical signal originally transmitted. Therefore, it is very important to accurately align the output beam of light source  60   a  to optical fiber  70  and the output beam from optical fiber  70  to light detector  60   b  at optical connectors  50   a  and  50   b , respectively. 
     Generally, light source  60   a  can be a laser diode (e.g. an edge emitting laser diode or a surface emitting laser diode) or LED and detector  60   b  can be a photodiode, although any other source of light or detection system can be used. An edge emitting laser diode should be diced for testing of the chip characteristics. A surface emitting laser diode, however, enables testing of chip characteristics on the wafer unit without dicing and is suitable for mass production. Additionally, surface emitting laser diodes have the advantage of requiring a lower driving current driver (e.g., laser driver  30 ) than edge emitting laser diodes. Also, because the light beam from an edge emitting laser diode is badly distorted with an elliptical shape, it is more difficult to couple the beam into the circularly shaped cross section of the optical fiber. An emitted light beam from a surface emitting laser diode can be the same circular shape as the cross section of the optical fiber and most of the light beam emitted can be coupled into the optical fiber. Therefore, surface emitting laser diodes are better suited for a passive alignment method because the passive alignment method is less accurate than the active alignment method. 
     Optical fiber  70  can be classified as single mode or multi-mode depending on a core size of optical fiber  70 , which is typically made from silica or plastic. A single mode optical fiber is more suitable than multi-mode optical fibers for high-speed, long-distance transmission of data. Optical fibers made from silica have better transmission properties, leading to less power loss, than optical fibers made from plastic. Because the core diameter of a single mode silica optical fiber is less than about 10 μm, it is very difficult to align source  60   a  to optical fiber  70  in order to couple light from light source  60   a  to optical fiber  70 . Therefore, connector  50   a  needs to be a high accuracy optical connector. Alternatively, a multi-mode optical fiber having a core diameter of more than 50 or 62.5 μm requires relatively little accuracy in alignment in order to couple light from source  60   a  to optical fiber  70 . A plastic optical fiber typically has a core diameter of about 250˜1000 μm and therefore it is relatively easy to couple light into and out of the plastic optical fiber. 
     FIG. 5 shows that the plastic optical fiber, with a core diameter of 0.5 mm, has an output power nearly 100% of the maximum output power even if the light beam from the light source is miss-aligned by about 100 μm from the center of the optical fiber. In contrast, if multi-mode optical silica fiber with a core diameter of 0.0625 mm is misaligned by approximately 20 μm, the output power of the optical fiber is sharply reduced. 
     As an additional difficulty, a typical photodiode utilized in high-speed transmission systems has a light receiving area with diameter of about 100˜200 μm. Because the photodiode has such a small diameter, optical fiber  70  needs to be precisely aligned with photodiode  60   b  in optical connector  50   b.    
     FIG. 6A shows one embodiment of an optical connector  620  in accordance with the present invention just prior to insertion into a optical device array block  622 , which can be mounted on a circuit board  624 . Connector  620  includes a multi-channel optical fiber block  626 , a stopper  628  and a housing  632 . Connector  620  provides accurate alignment of fibers  634  with optical devices  621 . Optical devices  621  can include any combination of light sources and detectors. The accurate placement of such optical devices in optical device array block  622  is discussed in copending U.S. application entitled “Multichannel Optical Transmitter/Receiver Module and Manufacturing Method Thereof” Ser. No. 09/608,207, filed Jun. 30, 2000, herein incorporated by reference in its entirety. Connector  620  also includes a cable  638  of rugged construction and strain relief for cable  638 . Multi-channel optical fiber block  626  captures fibers  634  and, when inserted in optical device array block  622 , aligns fibers  634  with optical devices  621  that are part of optical array device block  622 . Multi-channel optical fiber block  626  includes a V-groove block  652  (FIG. 7A) and a cover  666  (FIG.  7 A). Housing  632  is slidably mounted on cable  638  before stopper  628  is attached to cable  638 . 
     FIG. 6C shows a cross section of one embodiment of a cable  638  which contains fibers  634 . Cable  638 , for example, can be a Fiber Instrument Sales, Inc. Part Number 604-2N-CB-62PFD. Cable  638  of FIG. 6C includes a dielectric central strength member  706  surrounded by a central member upjacket  704 . Buffered optical fibers  634  are arranged around central strength member  706  and held in place by aramid yarn strength member  702 . Cable  638  is surrounded by outer jacket  700 . The Fiber Instrument Sales cable, for example, has a nominal diameter of 5.9 mm and 900 μm jacketed fiber  634  with a 0.0625 mm core within it. The diameter of Fiber Instrument Sales cable can be in the range of about 5.6 mm to about 9.4 mm. Although one particular embodiment of cable is described with a given nominal external diameter and having 900 μm buffered fibers having 0.0625 mm core, the present invention is adaptable to various nominal diameter cables. It is also adaptable to all fibers of any core diameter. 
     FIGS. 6D and 6E show one embodiment of the placement of stopper  628  on cable  638 . Stopper  628  includes a first portion  628   a  and a second portion  628   b  which fit over cable  638 . First portion  628   a  and second portion  628   b  form a passage  710  which is smaller than the diameter of cable  638 . First portion  628   a  and second portion  628   b  are positioned on cable  638  and, as shown in FIG. 6E, snapped into place, preventing the motion of cable  638  with respect to stopper  628 . In some embodiments, an adhesive is applied to better attach stopper  628  to outerjacket  700  of cable  638 . Although one example of stopper  628  is illustrated in FIGS. 6D and 6E, one skilled in the art will recognize that other stopper arrangements can be utilized. 
     FIG. 6B shows optical device array block  622  coupled to optical connector  620 . Multi-channel optical fiber block  626  is plugged into device array block  622 . Housing  632  is slid over cable jacket to contact stopper  628 . Stopper  628  is mounted at a predetermined position on cable  638  so that when housing  632  contacts stopper  628  flanges  646  of housing  632  are in contact with mounting plate  642  and fibers  634  are not strained. Mounting plate  642  is integral with optical device array block  622  and can be attached to optical device array block  622  or can be separately mounted to circuit board  624 . Screws  644  located on flanges  646  are tightened to attach housing  632  to mounting plate  642 . Other embodiments may use other attachment means to attach housing  632  to mounting plate  642 . After housing  632  is attached to mounting plate  642  cable holding buttons  648  are pushed into a locked position. Buttons  648 , in locked position, capture stopper  628  between the wall of housing  632  and buttons  648 . In this state, stopper  628  is prevented from rotating or translating, thus, cable  638  to which stopper  628  is attached fixedly cannot translate or rotate. Buttons  648  can also contact the jacket of cable  638  thereby aiding stopper  628  in preventing the translation or rotation of cable  638 . The cores of fibers  634  are aligned with optical devices  621 , which can be light sources  60   a  or detectors  60   b  (FIG.  4 ), in such manner as to reduce the loss of optical signal being transmitted to and from fibers  634 . By preventing translation and rotation of the cable, fibers  634  in the connection are strain relieved and thereby the interruption or degradation of signal transmission due to movement of the connector core  626  is reduced. 
     FIGS. 6F,  6 G and  6 H illustrate a connection between optical connector  620  and optical device array block  622 . In FIG. 6F, optical connector  620  is separated from optical device array block  622 . Mounting plate  642  is attached to optical device array block  622  and can further be attached to a panel (not shown) in order to provide panel connections. Optical device array block  622  includes metal leads  650  in order to provide electrical coupling to optical devices  621 . In FIG. 6G, multi-channel optical fiber block  626  is coupled into optical device array block  622 . Optical fibers  634  are aligned with optical devices  621  when multi-channel optical fiber block  626  is snapped into optical device array block  622 . In FIG. 6H, housing  632  is slid along cable  638  in order to fix stopper  628  within housing  632  and make contact with mounting plate  642 . Finally, housing  632  is attached (for example with screws  644 ) to mounting plate  642  and buttons  648  are depressed to lock stopper  628  in place relative to housing  632 . 
     FIG. 7A, FIG. 7B, and FIG. 7C are a plan view, an elevation, and a side view, respectively, of one embodiment of a multi-channel optical fiber block  626 . Multi-channel optical fiber block  626  of FIG. 7A includes a first portion  654  and a second portion  656 . First portion  654  receives a silicon V-groove block  664  having V-grooves  665  for positioning individual unjacketed optical fibers. V-grooves  665  in silicon V-groove block  664  have higher achievable tolerance for alignment of optical fibers  634  than V-grooves formed in conventional plastic molding and is amenable to mass production. V-grooves  665  having uniform intervals for aligning optical fibers  634  (FIG. 6A) can be made in V-groove block  664 , for example by using standard MEMS processing techniques. Second portion  656  has bores  662 , which are produce, for example, by plastic molding. When V-groove block is attacheably placed into first portion  654 , each V-groove  665  is aligned with one of bores  662  so that when bare fiber  634  is placed in V-groove  665  the center of fiber  634  is aligned with center of bore  662 . However, there can be minor misalignment between V-groove  665  and bore  662 . To ensure that fiber  634  are not subjected to excessive stress due to the misalignment, a trench  658  is located between V-groove  665  and bore  662 . One end of bore  662  is enlarged to facilitate application of epoxy. When assembled, a cover  666  is placed over first portion  656  and second portion  654  in order to protect and help hold optical fibers  634  in place. 
     FIGS. 7D,  7 E and  7 F are a plan view, an elevation, and a side view, respectively, of a second embodiment of a multi-channel optical fiber block  626 . Multi-channel optical fiber block  626  of FIGS. 7D,  7 E and  7 F include first portion  656  and second portion  654 . V-grooves  665 , however, are formed directly in second portion  654  instead of being separately produced in silicon V-block  664  (FIG.  7 A). Therefore, V-grooves  665  are produced in plastic along with the plastic portions of multi-channel fiber block  626  by plastic molding. The remaining portions of the second embodiment shown in FIGS. 7D,  7 E and  7 F are substantially identical with the first embodiment of FIGS. 7A,  7 B and  7 C. 
     FIGS. 7G,  7 H, and  71  are a plan view, an elevation, and a side view, respectively, of an example of cover  666  for multi-channel optical fiber block  626 . In one embodiment, cover  666  has a lip  720  so that a portion sites within the remainder of multi-channel optical fiber block  626 . In one embodiment, cover  666  is about 7.20 mm long, about 2.30 mm wide, and about 0.7875 mm deep. An about 0.25 mm deep lip  720  is formed along the longest edge. Lip  720  has a width of about 0.30 mm. 
     FIGS. 8A and 8B shows multi-channel optical fiber block  626 , cover  666  and fiber  634  placed in V-groove  665  through bore  662 . FIG. 8B illustrates how trench  658  helps reduce stress on fiber  634  when there is a misalignment between the V-groove  665  and the center of bore  662 . Trench  658  ensures that the transition of fiber  634  from bore  662  to V-groove  665  is not abrupt thereby assuring that fiber  634  is not stressed excessively due to bending. In the absence of trench  658 , as illustrated in FIG. 8A, fiber  634  will experience distortion at the junction of V-groove  665  and bore  662  and therefore fiber  634  can be stressed. High stress in fiber  634  results in high transmission loss for the optical signal and a reduction in useful life of the optical fiber. 
     FIG. 9 illustrates the method of capturing fiber  634  in multi-channel optical fiber block  626 . Fiber  634  is first stripped of its jacket to obtain bare fiber  635 . Fiber  634  along with bare fiber  635  is inserted in bore  662 . This would bring fiber  635 , the bare fiber portion of fiber  634 , in V-groove  665  and the jacketed portion of fiber  634  would be in bore  662 . Next, epoxy is inserted in each bore  662  through the bore&#39;s enlarged end, over each V-groove  665  and between cover  666  and V-grooves  665 . Cover  666  is placed over first portion having V-groove  664  and trench  658 . The epoxy is cured thereby capturing fibers  634  in block  652 . Cover  666  can be made from silicon. One advantage of this method over the conventional methods is that the jacket is captured in core  626 , thereby providing strain relief for fiber  635 . 
     FIG. 10 shows an assembled multi-channel optical fiber block  626  with retainer clip  670 . Multi-channel optical fiber block  626  is complementary to optical device array block  622 . Therefore, multi-channel optical fiber block  626 , when plugged into optical device array block  622 , locks in place to accurately align core of fibers  635  with optical devices  621  Connector  50   a  and  50   b  (FIG. 4) are similar in construction and can be interchangeable. They can be mass produced and can be used with any mass produced set of modules  61   a  and  61   b.    
     While particular embodiments of the present invention have been described it will be apparent to those skilled in the art that changes and modifications may be made without departing from this invention in its broader aspect. Therefore, the invention of this application is limited only by the following claims.