Abstract:
A connector for establishing a connection for use in a optical communications network, the connector comprising a plurality of optical elements, said optical elements being VCSELs, photodetectors or optical fibers, said optical elements being arranged in two or more arrays so that at least one of the arrays is moveable to ensure alignment of the members of that array when the connection is established.

Description:
FIELD OF THE INVENTION 
       [0001]    This invention relates to connectors for establishing optical communication links and, in particular, optical connector systems for establishing optical communication links between a parallel array of optical light emitters and/or photodetectors and a parallel array of fiber optic cables. 
       BACKGROUND OF THE INVENTION 
       [0002]    In optical communication systems information is transmitted in the form of modulated light beams through an optical transmission medium such as an optical fiber. The optical signals are produced by a modulated light source which may, for example, be a LED or a laser, and are detected at the receiving end by photodetectors. The present invention is concerned with connectors where such light sources and/or photodetectors are coupled to optical fibers. 
         [0003]    Advances in technology have resulted in light sources, photodetectors and optical fibers having relatively small cross-sections. It is therefore important when establishing a connection between such a light source or photodetector and an optical fiber that the fiber be correctly aligned with respect to the light source. Misalignment can result in attenuation of the power of the signal transmitted through the optical fiber or a complete break in communication. 
         [0004]    Connectors for establishing a connection between light sources or photodetectors and fiber optic cables may involve an array of light sources or photodetectors and an array of optical fiber cable ends. The connector acts by aligning the arrays. Certain of these kinds of connectors establish connections between two arrays of light sources and photodetectors and two corresponding arrays of optical fiber ends. It has been found however that the manufacturing tolerances in producing such connectors result in misaligned arrays when the connection is established. 
         [0005]    It is an object of the invention to address the aforementioned deficiencies. 
       SUMMARY OF THE INVENTION 
       [0006]    In accordance with a first aspect, the invention provides an optical connector for establishing a connection for use in a fiber optic network, said connector comprising a plurality of optical coupling arrays, said arrays comprising light emitters and/or light detectors, or fiber optical cable ends, said arrays being arranged for movement relative to one another. 
         [0007]    Relative movement of the arrays ensures that when an optical connection is established, all of the of the arrays may be properly aligned. This avoids loss or attenuation in signals which pass through the connection due to misaligned arrays. 
         [0008]    The movement of the optical connectors may be provided by a void, or by appropriate flexible material surrounding the array. 
         [0009]    Preferably, the connector includes registration element associated with each array to ensure that the corresponding array is properly aligned when a connection involving that array is made. 
         [0010]    A further aspect of the invention extends to a connection system comprising at least two mating connectors, wherein one of said connectors includes at least two optical arrays mounted for movement relative to one another. The first connector may comprise optical arrays of lasers and/or photodetectors, and the second connector may comprise parallel arrays of fiber optic cables. The fiber optic cables may form part of a fiber optic ribbon cable. 
         [0011]    Preferably the second connector is provided with separately movable ribbon cable arrays. Therefore, in a connector system comprising both emitter/photodetector and fiber optic connectors, it is preferable that the ribbon cable arrays be mounted for both linear and angular movement or displacement with respect to one another. 
         [0012]    Preferably the movement of the array relative to the connector is less than 5 mm in its linear extent. Further preferably the movement is less than 2 mm in its linear extent. 
         [0013]    By limiting the movement, failure of the respective connector attributable to excessive movement resulting in structural weaknesses may be minimized. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    Specific embodiments of the invention will now be described with reference to the accompanying drawings, in which: 
           [0015]      FIG. 1  is a perspective view of a known optical connector system; 
           [0016]      FIG. 2A  is a perspective view of a fiber optic connector of the optical connector system of  FIG. 1 ; 
           [0017]      FIG. 2B  is a perspective view of a detail of the optical connector system of  FIG. 1 ; 
           [0018]      FIG. 3  is a perspective view of a portion of a further known emitter; 
           [0019]      FIG. 4  is a perspective view of a portion of a further known emitter connector; 
           [0020]      FIG. 5  is a perspective view of a known optical connector system incorporating the emitter connector illustrated in  FIG. 4 ; 
           [0021]      FIG. 6  is a perspective view of a detail of the optical connector system of  FIG. 5 ; 
           [0022]      FIG. 7  is a perspective view of a fiber optic connector according to a first embodiment of the invention; 
           [0023]      FIG. 8  is a perspective view of a fiber optic connector according to a second embodiment of the invention; 
           [0024]      FIG. 9  is a perspective view of a fiber optic connector according to a third embodiment of the invention; and 
           [0025]      FIG. 10  is a perspective view of a fiber optic connector according to a fourth embodiment of the invention. 
       
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0026]      FIG. 1  illustrates an optical connector system  100  known in the art. The optical connector system  100  includes a fiber optic connector  200  which engages with an optical transceiver  300 . As described below in greater detail, the transceiver  300  comprises light sources and photodetectors and the fiber connector  200  comprises fiber optic cables. The connector system functions to establish a connection between these optoelectronic devices and fiber optic cables. 
         [0027]    The fiber optic connector  200  comprises a sleeve  210  connected to the ribbon cable  220 . The sleeve  210  therefore acts to anchor the fiber optic connector  200  to the ribbon cable  220 . At one end of the transceiver  300  there is provided a locking portion  310  having two snap-fit hooks  312  and  314  which engage with corresponding formations provided on the fiber optic connector  200  (not shown in  FIG. 1 ) to ensure that the fiber optic connector  200  securely connects with the transceiver  300 . 
         [0028]      FIG. 2A  illustrates the fiber optic connector  200  of  FIG. 1  in greater detail. The fiber optic connector  200  (shown here without sleeve  210 ) includes a mounting  240  which supports, and to which is mounted, a fiber optic front-end  230 . The fiber optic front-end  230  is formed with two receptacles (only one of which, receptacle  232 , is shown in  FIG. 2A , the other receptacle being located at a diametrically opposed position to receptacle  232 ). These receptacles receive the snap-fit hooks  312  and  314  of the emitter connector  300  ( FIG. 1 ) to form the connection between fiber optic connector  200  and transceiver  300 . Fiber optic ribbon cable  220  (not shown in this Figure) comprises a set of fiber optic strands, the ends of which are arranged in an optical fiber array  203 . The optical fiber array  203  is mounted on the front-end  230 . Two sockets  201  and  202  are formed in the fiber optic front-end  230  and are provided to either side of the optical fiber array  203 . 
         [0029]      FIG. 2B  illustrates a detail of the known optical connector system  100  of  FIG. 1 . The transceiver  300  of connector system  100  includes an array  330  of vertical cavity surface emitting lasers (VCSELs). The array  330  is mounted in and supported by array support  320  which is part of emitter connector front-end  332 . Disposed on either side of the array  330  are two pins  316  and  318  connected to array support  320 . When the transceiver  300  engages with the fiber optic connector  200 , pins  316  and  318  engage with respective sockets  201  and  202 . This ensures that the optoelectronic devices of array  330  will align with the fiber optic array  203  so that light beams associated with the VCSELs or detectors of array  330  will be received and transmitted by the optical fibers of array  203  without significant attenuation in the power of the light beams. 
         [0030]      FIG. 3  illustrates a further emitter connector  350  known in the art. Emitter connector  350  includes two arrays  352  and  354  (e.g. emitters and detectors) which operate in parallel, increasing the throughput of the connection established by the connector  350  in comparison to that established with the connection system  100  of  FIG. 1 . Emitter connector  350  includes pins  356  and  358  to ensure alignment of each of the arrays  352  and  354  with corresponding fiber optic arrays. However, the problem of alignment is significantly exacerbated where two arrays are involved, and it has been found that the arrangement illustrated in  FIG. 3  provides insufficient registration for alignment between the optoelectronic devices of the arrays  352  and  354  and the optical fiber ends of corresponding fiber optic arrays. 
         [0031]      FIG. 4  illustrates a further transceiver connector  360  known in the art. Similar to the transceiver connector  350  illustrated in  FIG. 3 , connector  360  includes two arrays  352  and  354 . However, to improve alignment, connector  360  is provided with four pins  362 ,  364 ,  366  and  368 . As illustrated in greater detail in  FIG. 5 , the connector  360  connects to a fiber optic connector  380  to form optical connector system  500 . Optical connector system  500  is illustrated in further detail in  FIG. 6 . As illustrated in  FIG. 6 , the fiber optic cable connector  380  is provided with two fiber optic cable arrays  382  and  384  with corresponding sockets  390  and  392  disposed on either side of fiber optic array  382 , and sockets  394  and  396  disposed on either side of fiber optic array  384 . When the connector  360  engages with the fiber cable connector  380  the pins  362 ,  364 ,  366  and  368  engage with respective sockets  392 ,  394 ,  390  and  396 . 
         [0032]    However, it has been found that the structure described above and illustrated in  FIGS. 5 and 6  provides insufficient alignment between the VCSELs of the VCSEL arrays, and the photodetectors of the photodetector array, and corresponding fiber optic ends of the fiber optic cable arrays. Manufacturing tolerances for such a connector system exceed the required accuracy for establishing efficient optical connections. 
         [0033]      FIG. 7  illustrates a fiber optic cable connector  700  according to a preferred embodiment of the invention. Connector  700  includes fiber optic module  730  attached to a mounting  740 . Although not illustrated in  FIG. 7 , the mounting  740  is attached to a fiber optic ribbon cable in the manner illustrated with respect to the fiber optic module  200  of  FIG. 1 . 
         [0034]    The fiber optic module  730  includes a module front-end  732 . Module front-end  732  comprises upper half-cap  734  and lower half-cap  736 . Upper half-cap  734  includes a fiber optic array  710  mounted in a fiber optic array support  714 . Similarly, lower half-cap  736  includes fiber optic array  712  mounted in fiber optic array support  716 . Lines  740  and  742  show horizontal center lines for the respective fiber optic arrays  710  and  712 . Disposed on either side of fiber optic arrays  710  and  712  are respective pairs of sockets:  718  and  720 ; and  722  and  724 . A flexible member  750  is provided between upper half-cap  734  and lower half-cap  736 . 
         [0035]    The fiber optic connector  700  may be utilized with the connector  360  illustrated in  FIGS. 5 and 6 . In use, when the fiber optic connector  700  is engaged with connector  360 , the pins  362  and  366  will engage with sockets  720  and  718  to ensure that the VCSEL array  352  aligns with optical fiber array  710 . Similarly, pins  368  and  364  of the emitter connector  360  engage with sockets  722  and  724  to ensure that the photodetector array  354  aligns with optical fiber array  712 . The pins and sockets provide registration element to ensure that the respective pairs of VCSELs/photodetectors and optic fiber arrays are aligned. The flexible member  750  provides a limited degree of movement between upper half-cap  734  and lower half-cap  736  which, in turn, provides a degree of movement between the two optical fiber arrays  710  and  712 . Therefore when the optical fiber connector  700  engages with the emitter connector  360 , accurate alignment between the respective arrays is ensured. 
         [0036]    In the embodiment herein described a pin and socket arrangement such as pins  368 ,  364  and sockets  722 ,  724  provide a registration element. As the pins engage with the respective sockets, the arrays will move (as provided for by the flexible members) to provide the required connection between the arrays. Although pins and sockets have been described herein as the means by which the arrays are aligned, other means may other be used. In its simplest form this registration may be provided by any two engaging members where one of the members is attached to the VCSEL/photodetector array (preferably by means of the array support) and the other member to the fiber optic array (preferably also by means of the array support). In a more complex arrangement, registration is provided by interengaging members such as the snap-fit members previously described or by a guide member which engages with each one of the arrays of corresponding pairs (by means of the array support or otherwise). In a further embodiment, both the VCSEL/photodetector array and the corresponding fiber optic array are mounted for movement. In this case the registration may be provided as previously described. 
         [0037]    The flexible member  750  of  FIG. 7  is disposed and constructed so that the movement of fiber optic array  710  relative to fiber optic array  712  is constrained to a total linear movement of 2 mm from a rest position (defined by movement of respective center lines  740  and  742 ). In practice, manufacturing tolerances will vary this degree of relative movement so that certain fiber optic connectors constructed in accordance with the invention may display a linear movement of 4 mm. 
         [0038]      FIG. 8  illustrates a further embodiment of the invention. Fiber optic connector  800  comprises a module  830  having a module front-end  832 . Front-end  832  comprises upper half-cap  860  and lower half-cap  850 . The half-caps  850  and  860  differ from those illustrated in  FIG. 7  ( 732  and  734 ) in that the half-caps  850  and  860  each include a respective flexible material member  854  and  864  surrounding respective fiber optic array supports  814  and  816 . A rigid support member  852  is attached to the flexible material members  854  and  864  and to module  830 . The flexible members  854  and  864  therefore allow the fiber optic arrays  810  and  812  to move relative to one another and relative to the rigid support member  852 . 
         [0039]      FIG. 9  illustrates a fiber optic connector  900  according to a further embodiment of the invention. Fiber optic connector  900  includes a fiber optic module  930  having a front-end  932 . Front-end  932  includes half end-caps  950  and  960 . Upper half-cap  960  includes a fiber optic array  910  mounted in fiber optic array support  914 . Lower half-cap  950  includes a fiber optic array  912  mounted in fiber optic array support  916 . 
         [0040]    The embodiment of  FIG. 9  differs from that illustrated in  FIG. 8  in that the fiber optic connector  900  includes a rigid frame structure  954  disposed around an outer periphery of the front-end  932 . The frame structure  954 , together with a rigid support member  952  (which is located centrally within the front-end  932 , and which corresponds to the rigid support member  852  of the embodiment of  FIG. 8 ), define respective receptacles for flexible members  956  and  964 . The flexible members  956  and  964  allow the fiber optic arrays  910  and  912  to move relative to one another and relative to the flexible frame  954 , and support member  952 . 
         [0041]      FIG. 10  illustrates a fiber optic connector  1000  according to a further embodiment of the invention. Fiber optic connector  1000  includes a fiber optic module  1030  having a front-end  1032 . Front-end  1032  half end-caps  1050  and  1060 . Upper half-cap  1060  includes a fiber optic array  1010  mounted in fiber optic array support  1014 . Lower half-cap  1050  includes a fiber optic array  1012  mounted in fiber optic array support  1016 . 
         [0042]    The fiber optic connector  1000  includes a rigid frame structure  1054  disposed around an outer periphery of the front-end  1032 . The frame structure  1054  defines a receptacle within which flexible members  1056  and  1064  are housed. As with previous embodiments, the flexible member  1056  and  1064  provide movement of the fiber optic arrays  1010  and  1012  relative to one another and relative to the frame structure  1054 . In an alternative embodiment, the flexible members  1056  and  1064  may be replaced by a single flexible member. 
         [0043]    The embodiment illustrated in  FIG. 10  differs from that illustrated in  FIG. 9  in that it lacks a support member corresponding to rigid support member  952 . 
         [0044]    In each of the aforementioned embodiments one or more flexible members is provided to allow movement of two fiber optic arrays relative to one another. Changes to the above embodiments are possible and within the scope of the invention. For example, the flexible member or members may be omitted altogether to provide a void instead. It will be realized that a void would also permit relative movement, albeit in a less controlled manner than provided by a flexible member. A person skilled in the art will realize that there are many materials suitable for constructing a flexible member such as foam, rubber etc. 
         [0045]    It is further to be realized that the aforementioned embodiments have been described with reference to a connector which comprises arrays of optical fiber. However, the principles of the invention are equally applicable to a connector which alternatively or additionally includes other optoelectronic elements such as arrays of photodetectors and/or of optical emitters such as VCSELs. Similarly, the VCSEL arrays described above may equally be photodetectors arranged in arrays.