Abstract:
An opto-mechanical switching device for selectively switching an optical input between a plurality of output fibers. The opto-mechanical switching device includes a re-directing fiber adapted to receive the optical input. The re-directing fiber is disposed within a re-directing fiber housing. The re-directing fiber housing is selectively positionable via a stepper motor to transmit the optical input to a predetermined one of the plurality of output fibers. A method for switching an optical input between a plurality of output fibers is also provided.

Description:
TECHNICAL FIELD 
     The present invention generally relates to optical switches and more particularly to an optical switch and a switching method therefor for the switching of an optical signal through the use of a selectively positionable re-directing fiber. 
     BACKGROUND OF THE INVENTION 
     BACKGROUND ART 
     In applications involving the transmission of optically encoded data through fiber optic cables, there is frequently a need to selectively switch data between an input fiber and two or more output fibers. A simple way to provide optical fiber switching has been to perform the switching manually. This may be accomplished, for example, by manually manipulating a switchboard panel. This solution, however, is limited to applications where the number of output fibers to be switched between is relatively small and a relatively slow switching time is acceptable. 
     Switching applications that require more rapid response and/or a relatively large number of output fibers typically employ an automated switching device. One kind of automated switching device is an opto-mechanical switching device. Opto-mechanical switching devices typically employ a lensed input fiber which is mechanically moved across a bank of lensed output fibers. Data is transferred when the lensed input fiber is aligned with a lensed output fiber. 
     Opto-mechanical switching devices typically have a switching response on the order of 10 to 50 ms, which is far better than that which is possible for a manually operated switchboard panel. Furthermore, opto-mechanical switches generally exhibit good cross talk, back reflection and insertion loss characteristics. 
     One drawback associated with conventional opto-mechanical switches concerns the ease and cost with which they are integrated into a circuit. Generally, the microlenses of a conventional opto-mechanical switch must be aligned to each fiber and testing must be performed to verify that the alignment is proper. In applications requiring relatively large switches, the cost of fiber alignment is a dominant cost and may easily exceed the cost of the switch itself. 
     One attempt to reduce the costs associated with opto-mechanical switching devices is disclosed in U.S. Pat. No. 5,621,829 entitled “Fiber Optic Switching Device and Method Using Free Space Scanning”, the disclosure of which is hereby incorporated by reference as if fully set forth herein. The device of the &#39;829 patent employs a moving reflective mechanism, such as a reflector or a prism, to transfer a collimated light signal from the input fiber to a desired output fiber. This approach, however, has, several drawbacks. One drawback associated with the approach disclosed in the &#39;829 patent concerns the efficiency with which light is transmitted from the input fiber to an output fiber. The use of reflective mechanisms typically results in a total internal reflection or loss in efficiency of about 5 to 15 percent for the best reflective surfaces. Losses may be substantially higher for lower quality reflective surfaces, rendering it even more likely that the input signal will not be accurately transmitted to the preselected output fiber. 
     Another drawback concerns the relative cost of the device disclosed in the &#39;829 patent. Reflective mechanisms, especially those having good quality reflective surfaces, are typically expensive and as such, tend to increase the initial cost of the switching mechanism. Furthermore, periodic maintenance or cleaning of the reflective surface is required to maintain optical performance of the reflective mechanism and ensure maximum light transmission from the input fiber to the preselected output fiber. 
     SUMMARY OF THE INVENTION 
     It is one object of the present invention to provide an opto-mechanical switching device which does not require extensive alignment between an input fiber and a plurality of output fibers. 
     It is another object of the present invention to provide an opto-mechanical switching device which does not require expensive reflective mechanisms for transmitting an optical input to a predetermined output fiber. 
     It is a more specific object of the present invention to provide an opto-mechanical switching device which employs a re-directing fiber to accurately and efficiently transmit an optical input to a predetermined output fiber. 
     It is yet another object of the present invention to provide a method for switching an optical signal between a plurality of output fibers using a re-directing fiber. 
     In one preferred form, the present invention provides an opto-mechanical switching device for selectively switching an optical input between a plurality of output fibers. The opto-mechanical switching device includes a re-directing fiber adapted to receive the optical input. The re-directing fiber is selectively positionable to transmit the optical input to a predetermined one of the plurality of output fibers. A method for switching an optical input between a plurality of output fibers is also provided. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Additional advantages and features of the present invention will become apparent from the subsequent description and the appended claims, taken in conjunction with the accompanying drawings, wherein: 
     FIG. 1 is a perspective view of an opto-mechanical switching assembly constructed in accordance with a preferred embodiment of the present invention; and 
     FIG. 2 is a partial sectional view of the opto-mechanical switching assembly of FIG. 1 taken along the line  2 — 2 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     With reference to FIG. 1 of the drawings, an opto-mechanical switching device constructed in accordance with the teachings of a preferred embodiment of the present invention is generally indicated by reference numeral  10 . Opto-mechanical switching device  10  is shown to include a separator member  12 , a plurality of output fibers  14 , an output fiber connector  16 , a re-directing fiber  18 , a re-directing fiber housing  20  and a drive mechanism  22 . 
     With additional reference to FIG. 2, separator member  12  is shown to include a plurality of holes  30 , each of which is sized to receive one of the plurality of output fibers  14 . In the particular embodiment illustrated, separator member  12  is an annular plate and the plurality of holes  30  are spaced apart around the circumference of a circle formed concentrically about the central axis  34  of opto-mechanical switching device  10 . 
     The plurality of output fibers  14  are conventional fiber optic cables that are positioned in the holes  30  in the separator member  12  and fixedly coupled thereto by a conventional securing means such as an adhesive. The distal end  40  of the plurality of output fibers  14  is coupled to output fiber connector  16  in a manner that is well known in the art. Output fiber connector  16  permits opto-mechanical switching device  10  to be quickly and accurately coupled to an optical circuit (not shown) without the need for aligning opto-mechanical switching device  10  to fiber optic cable elements of the optical circuit. 
     Re-directing fiber  18  is shown in the particular embodiment illustrated to include a first portion  50  which is generally coincident with the central axis  34 , a second portion  52  which is generally parallel to the first portion  50  and radially outwardly offset therefrom, and a third or central portion  54  which extends between the first and second portions  50  and  52 . Re-directing fiber  18  is molded into or otherwise fixedly coupled to re-directing fiber housing  20 . Re-directing fiber housing  20  is therefore operable for maintaining the shape of the re-directing fiber  18  as well as protecting the re-directing fiber  18  from contact with foreign objects which would tend to abrade the sides of the re-directing fiber  18 . 
     Drive mechanism  22  is coupled to re-directing fiber  18  and is selectively operable for moving the re-directing fiber such that the second portion  52  of the re-directing fiber  18  is aligned to the proximal end  60  of a predetermined one of the plurality of output fibers  14 . In the particular embodiment illustrated, drive mechanism  22  includes a conventional stepper motor  64  and a conventional controller  68 . Stepper motor  64  may be a permanent magnet or variable reluctance type stepper motor, with the angular resolution of each step preferably correlating to the angular spacing between the holes  30  in the separator member  12 . Stepper motor  64  includes a housing  70  that is fixedly coupled to separator member  12  in a predetermined radial relationship. Stepper motor  64  also includes an output member  72  that is rotatable about the central axis  34 . Controller  68  is coupled to stepper motor  64  and causes stepper motor  64  to rotate output member  72  to a predetermined rotational position. Alternatively, drive mechanism  22  may include a conventional servo motor or other rotary actuator which permits a rotational output member to be accurately positioned in a plurality of predetermined radial positions. It will be appreciated that virtually any component that performs the function of precisely rotating the fiber housing  20  to precise angular positions could be used to form the drive mechanism  22 . 
     In operation, an opto-mechanical switching device  10  is mounted in a desired location, an input fiber  74  is aligned to the first portion  50  of the re-directing fiber  18  and the output fiber connector  16  is coupled to a fiber optic circuit. As those skilled in the art will understand, the gap between the input fiber  74  and the first portion  50  of the re-directing fiber  18  as well as the respective gaps between the second portion  52  of the re-directing fiber  18  and the proximal end  60  of the plurality of output fibers  14  are preferably controlled to be both uniform and as small as possible to prevent contact between the ends of the fibers while maximizing signal transmission between the respective fibers. Those skilled in the art will also understand that signal transmission between the respective fibers can be maximized through proper preparation of the ends of the fibers (e.g., trimming the ends perpendicular to the longitudinal axis of the fiber). Input fiber  74  provides an optical input signal that is received by the first portion  50  of re-directing fiber  18 . The optical input signal is transmitted through the re-directing fiber  18  where it exits the second portion  52  of the re-directing fiber  18 , and then enters the proximal end  60  of a first one of the plurality of output fibers  14  (e.g., output fiber  14   a ). When switching is required, controller  68  causes the stepper motor  64  to rotate re-directing fiber  18  to a precise, predetermined position such that the second portion  52  of the re-directing fiber  18  is aligned to the proximal end  60  of a preselected second one of the plurality of output fibers  14  (e.g., output fiber  14   b ). 
     Advantageously, this approach does not rely on reflective mechanisms. As such, total internal reflection results in a loss in efficiency of only about 1 percent or less, thus substantially increasing the reliability with which data may be accurately transmitted to an output fiber. Furthermore, as the re-directing fiber housing  20  and the separator member  12  cooperate to align the second portion  52  of the re-directing fiber  18  to the proximal ends  60  of the plurality of output fibers  14 , the cost associated with the process of aligning fibers is substantially reduced, with the only necessary field alignment being between the first portion  50  of the re-directing fiber  18  and the input fiber  74 . 
     While the invention has been described in the specification and illustrated in the drawings with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention as defined in the claims. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment illustrated by the drawings and described in the specification as the best mode presently contemplated for carrying out this invention, but that the invention will include any embodiments falling within the foregoing description and the appended claims.