Abstract:
An optical beam switch is designed for improved serviceability by mounting two fiber optic beam deflection arrays to face the front of a rack assembly. Inside the optical beam switch, a reflecting device is located behind each of the two fiber optic beam deflection arrays and used to reflect the light beams between the two fiber optic beam deflection arrays. Front access to the two fiber optic beam deflection arrays is then readily available whether the optical beam switch is mounted horizontally or vertically in the rack assembly.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     Related subject matter is disclosed in the pending application entitled “STRICTLY NON-BLOCKING SCALABLE MATRIX OPTICAL SWITCH” filed on Feb. 20, 1998 by B. H. Lee, Ser. No. 09/026,856, now U.S. Pat. No. 6,005,998, which is assigned to the same assignee as the present application. 
     TECHNICAL FIELD OF THE INVENTION 
     The present invention relates to optical switches, and more particularly, to an optical switch that is arranged to be accessible from the front when mounted in a rack assembly. 
     BACKGROUND OF THE INVENTION 
     In optical transmission, applications exist wherein numerous optical signals carried by respective optical fibers must be switched or routed to a corresponding number of output fibers. Optical cross-connects have been used to provide this optical switching function. The U.S. Pat. No. 5,206,497, issued on Apr. 27, 1993 to B. H. Lee describes an optical cross-connect that uses a free-space optical switching apparatus. 
     Another type of optical cross-connect can be implemented using a large optical beam steering switch designed by using motor driven beam deflection clusters. Such an arrangement is disclosed in the pending application entitled “STRICTLY NON-BLOCKING SCALABLE MATRIX OPTICAL SWITCH” filed on Feb. 20, 1998 by B. H. Lee, Ser. No. 09/026,856, and assigned to the same assignee as the present application. In one of the Lee arrangements, the beam deflection clusters are mounted on both ends of the beam steering switch. When this optical beam switch is mounted horizontally in an integrated rack assembly, as shown in FIG. 1, access from the sides is required to replace the clusters. However, this violates the frontal accessibility requirement often specified by customers. Horizontal mounting also requires that the optical beam switch span across several integrated rack assemblies, because of its large size. Handling and transportation of the optical beam switch also becomes more difficult. Meeting Telcordia&#39;s Network Equipment Building Systems (NEBS) Requirements (e.g., GR-63-CORE, Issue 1) also becomes exceedingly difficult. These problems also increase when the cross-connect size increases. 
     When the optical beam switch is mounted vertically in a rack assembly, as shown in FIG. 2, then access to the beam deflection clusters requires access via the top and bottom, which is also not easy because of the size of the optical beam switch and the limited space in the rack assembly. 
     What is needed is an optical beam switch of reduced size and improved accessibility when mounted in a rack assembly. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention, a fiber optic beam switch apparatus is designed for improved serviceability by mounting two fiber optic beam deflection arrays (or clusters) to face the front of a rack assembly. Inside the optical beam switch, a reflecting device is located behind each of the two fiber optic beam deflection arrays and used to reflect the light beams between the two fiber optic beam deflection arrays. Front access to the two fiber optic beam deflection arrays is then readily available whether the optical beam switch is mounted horizontally or vertically in the rack assembly. 
     More specifically, my fiber optic switch apparatus comprises (1) a first fiber optic beam deflection array mounted to a front face of the fiber optic switch apparatus, (2) a first reflecting device, positioned behind the first fiber optic beam deflection array at about forty five degree angle to the first fiber optic beam deflection array, reflects optical beams received from the first fiber optic beam deflection array, (3) a second fiber optic beam deflection array is mounted to the front face of the fiber optic switch apparatus and disposed along the front face at an appropriate distance away from the first fiber optic beam deflection array, and (4) a second reflecting device, positioned behind the second fiber optic beam deflection array at about forty five degree angle to the second fiber optic beam deflection array, receives reflected optical beams from the first reflecting mirror and further reflects those reflected beams to the second fiber optic beam deflection array. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings, 
     FIG. 1 shows an optical beam steering switch mounted horizontally in a rack assembly and having cluster assemblies requiring access from the sides; 
     FIG. 2 shows an optical beam switch mounted vertically in a rack assembly and having cluster assemblies requiring access from the top and bottom; 
     FIG. 3 shows, in accordance with my invention, an optical beam switch mounted vertically in a rack assembly and having cluster assemblies having access from the front; and 
     FIG. 4 shows a side view of my optical beam switch, showing the mounting of the mirror and cluster assemblies. 
    
    
     In the following description, identical element designations in different figures represent identical elements. Additionally in the element designations, the first digit refers to the figure in which that element is first located (e.g.,  103  is first located in FIG.  1 ). 
     DETAILED DESCRIPTION 
     Shown in FIG. 1 is an optical beam steering switch  101  mounted horizontally across the inside of several bays  110 - 112  of a rack assembly  102  and having cluster assemblies  103  and  104 . The cluster assemblies  103  and  104  may be implemented using beam deflection clusters of the type shown, in FIG. 7, and described in the previously-referenced B. H. Lee pending application, which is incorporated by reference herein. The connection of optical fibers to the cluster assemblies  103  and  104 , require access by going to the side of the rack assembly  102  and accessing the clusters from the side of the optical beam steering switch  101 . Maintenance of cluster assemblies  103  and  104 , including removal, addition and replacement the cluster assemblies, also require access by going to the side of rack assembly  102  to access the cluster assemblies. However, access through the side may be extremely difficult in a central office if there are other racks of equipment next to the switch rack assembly  102 . 
     Shown in FIG. 2 is an optical beam switch mounted vertically in a rack assembly and having cluster assemblies requiring access from the top and bottom. In this arrangement, access to clusters  103  and  104  require sufficient clearance between the optical beam steering switch  101  and the top and bottom, respectively, of the rack assembly  201 . Since a typical measurement for a  512  port optical fiber cluster assembly is about 68 inches in length,  201 , and a typical height of a of a rack assembly is about 84 inches, only about 8 inches are available to provide access to either of the top  103  or bottom  104  cluster. 
     FIG. 3 shows, in accordance with my invention, an illustrative optical beam switch  101  mounted vertically in a rack assembly  201  and having cluster assemblies  103  and  104  which face the front. As shown, access to the cluster assemblies  103  and  104  is readily accomplished from the front of rack assembly  201 . Even if the optical beam switch  101  is mounted horizontally, the cluster assemblies are readily accessible from the front. 
     With reference to FIG. 4, there is shown a side view of my optical beam switch  101  showing the mounting of the cluster assemblies  103  and  104  and associated mirror assemblies  401  and  402 , respectively. Illustratively, the mirror assemblies may be front surface infrared (FSIR) mirrors. As shown, the cluster assemblies  103  and  104  are mounted on a front face  150  of optical beam switch  101  and the mirror assemblies are mounted to form about a forty five degree angle with the front face of optical beam switch  101 . The illustrative first optical beam  403  traces a path that originates at optical cluster unit  404  in cluster assembly  103 , is reflected by mirror assembly  401  to mirror assembly  402  where it is reflected to at optical cluster unit  405  in cluster assembly  104 . In this example, the optical path  403  exits the optical cluster unit  404  and enters optical cluster unit  405  essentially perpendicular to the respective cluster assemblies,  103  and  104 . 
     The illustrative second optical beam  406  traces a path that originates at optical cluster unit  404 , is reflected by mirror assembly  401  to mirror assembly  402  where it is reflected to optical cluster unit  407  in cluster assembly  104 . In this example, for optical cluster  104  to send an optical beam to optical cluster unit  407 , the optical path  406  must exit optical cluster unit  404  in a non-perpendicular angle and must enter optical cluster unit  407  in a non-perpendicular angle. The controller  410  controls the deflection angles for all of the optical cluster units of cluster assemblies  103  and  104 . To establish an optical connection, controller  410  accesses a data base to obtain the proper sending and receiving angle to enable any optical cluster unit of cluster assembly  103  to reach any optical cluster unit of cluster assembly unit  104 . The objective is to have the axis of the receiving clusters (the collimator) align with the received optical beam. Since the sending and receiving angles needed for my arrangement of FIG. 4 are different from those required by the arrangements of Figs land  2 , the sending and receiving angle data used by controller  410  must be changed accordingly. 
     Note that the distance  420  is determined by optical and mechanical design. The design is influenced by the size of the cluster assembly arrays  103  and  104 . The objective should be for the beam switch  101  to fit inside of a standard equipment rack assembly  102 . Depending on the technology used in the cluster assemblies  103  and  104 , the distance may be reduced to almost zero length. 
     Software programs are used by controller  410  to automate the generation of the appropriate sending and receiving angles needed. The controller  410  is typically located in an adjacent equipment rack. To facilitate such programs the mirror assemblies  401  and  402  can be made to be partially transmissive and optical sensors can be mounted at the rear of the front surface mirror of one or more of the mirror assemblies  401  and  402  to monitor the optical beams. The feedback from these optical sensors may then be used by the software program to set the proper sending and receiving angles for the optical cluster units to accomplish any optical switching connection between any two optical cluster units of cluster assemblies  103  and  104 . The optical sensors can also be used for general signal monitoring purposes such as monitoring drift and failure of the optical beams. 
     Note, that while the cluster assemblies  103  and  104  are shown to be flatly mounted to the face of optical beam switch  101 , if desirable, they could be mounted on a convex spherically surface (in the manner shown in FIG. 10 of the previously-referenced patent application. The important objective is to align, as much as possible, the axes of the transmitting and receiving optical units. It should also be noted that the present invention can operate with a variety of fiber optic beam deflection arrays besides the cluster assemblies  103  and  104  described in FIG. 7 of the previously-referenced patent application and those described in FIG. 1 of U.S. Pat. No. 5,206,497. While the mirror has been described to reflect the optical beams, other types of reflecting devices may also be used depending on the optical requirements. 
     What has been described is merely illustrative of the application of the principles of the present invention. Other methods and arrangements can be implemented by those skilled in the art without departing from the spirit and scope of the present invention.