Abstract:
The present invention provides switch arrays for use in optical communication systems. The switch arrays are illustrated in relatively simple and relatively complex versions for each of two types. Each switch array is assembled by connecting of plural optical switches to each other and to transmission links and packet switches accordingly. The result enables handling a greater quantity of signal volume.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to the field of optical communication signal switching, and more particularly to arrangements for an array of switches to create a complex switch.  
         BACKGROUND OF THE INVENTION  
         [0002]    Optical communication signals rely on laser light beams to transmit data. Laser beams are considered to be coherent, or linear, light. As such, they do not tend to diffuse to the same degree as ordinary light. Ordinary light will diffuse to the extent that its power per unit area will diminish in proportion to the square of the distance over which it travels.  
           [0003]    Modern optical communication consists of digitized signals that comprise a message or data portion and an identifying portion. The identifying portion, often referred to as a header, provides information for assembling a number of message components into a complete message as well as the intended destination of the message, e.g. an email address. When a communication controller such as a computer receives and analyzes a message header, the controller routes the message to direct it to the intended destination. This routing involves causing the message to be switched at various junctions from an incoming transmission cable to a different outgoing transmission cable.  
           [0004]    Optical switches are known in rudimentary forms, such as 4×4, 8×8, or 16×16 ports. This nomenclature indicates that, in the first example, four input cables and four output cables are connected to a switch to allow signals to be routed straight through or diverted in direction to a different route. However, as communication by optical signal grows, greater complexities of switches are needed to handle the volume. It has yet been impractical to build a single 32×32 port or larger switch because of difficulties in maintaining the direction of an optical signal with sufficient accuracy to maintain its power and transmitted data in tact.  
           [0005]    Therefore, it is an object of the present invention to provide an optical switch array that conveys and routes a large number of optical messages.  
           [0006]    This and other objects will become more apparent from the description of the invention to follow.  
         SUMMARY OF THE INVENTION  
         [0007]    The present invention provides arrays of optical switches connected so as to control the movement of messages in a communication system. Micro electro mechanical system (MEMS) switches or Optical Switch Modules (OSMs) are connected in an array to grow capacity and retain flexibility. Messages are transmitted, added to or deleted from through optical switch manipulation.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]    [0008]FIG. 1 is a schematic diagram of a 32×32 optical switch array utilizing 16×16 switch components.  
         [0009]    [0009]FIG. 2 is a schematic diagram of a 64×64 optical switch array utilizing 16×16 switch components.  
         [0010]    [0010]FIG. 3 is a schematic diagram of an 8×8 optical switch array.  
         [0011]    [0011]FIG. 4 is a schematic diagram of a 32×32 optical switch array utilizing 8×8 switch components. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0012]    The present invention provides an optical switch array by description of the following exemplary group of switch arrays. The switch array of the invention utilizes multiple switch components each having a small number of optical ports in a combination enabling an expanded number of ports in the array. Messages or signals are typically transmitted as a plurality of TCP packets that each comprise a data portion and an identifying header. When an optical signal packet arrives at a switch point in an optical circuit, the packet header is parsed for information regarding its intended destination so as to be routed accordingly. Instructions are generated according to the intended destination and the available line capacities.  
         [0013]    As illustrated in FIG. 1, a switch array includes optical switch module (OSM)  12  and OSM  16 . Each of OSM  12  and OSM  16  is an assembly of switch components as shown in FIG. 3, described below. OSM  12  and OSM  16  are each two-plane 16×16 switch modules, that is they are each capable of receiving and transmitting 16 optical signals through two planes, or sets of connective ports. OSM  12  receives and transmits optical signals  14 , noted as p 1  through p 8  and OSM  16  receives and transmits optical signals  18 , noted as p 9  through p 16 . By indicating eight ports of both receiving and transmitting, each module has a total of 16 ports for adding and dropping, i.e. receiving signals from or sending signals to networks and terminal devices. Add/drop ports p 1  through p 16  are connected to local packet switches to add signals to or drop signals from the optical transmission circuit, such signals typically being handled in packets under TCP/IP procedures, as is known. Each of OSM  12  and  16  is capable of connecting any input signal to any output port at the same or a different wavelength as the wavelength received. The diversion of signal routing is accomplished within the OSMs according to instructions generated by a controller (not shown). Thus, 16×16 OSM  30  and 16×16 OSM  32  provide a 32×32 OSM assembly (32 ports in and 32 ports out) when optically connected as illustrated. OSM  30  and OSM  32  are shown as four-plane modules for possible array expansion, but only two planes of each are connected herein. OSM  32  receives input signals  34   b  from a communication network connected by optical fiber as a multiplexed transmission of multiple wavelengths λ 1 -λ 16 . The optical switches include apparatus to multiplex and demultiplex signals. OSM  32  directs selected ones of the signals to OSM  12  via transmission link  22   b  and others to OSM  16  via transmission link  24   b.  OSM  12  and OSM  16  each route the received signals either to drop lines  14  or  18  or to OSM  30  through transmission link  22   a  or transmission link  24   a.  Packets received into OSM  30  are diverted to appropriate ports and sent onward via output signals  34   a.  As it is illustrated, array  10  is formed as an assembly of three optical switches connected in series with each other. The transmitting wavelengths may be the same as or different than the receiving wavelengths.  
         [0014]    Since the fundamental object of the present invention is to achieve increased optical signal processing capacity in a modular system, FIG. 2 provides a switch array that utilizes the principles of FIG. 1 above in greater size and capacity. It will be apparent to those skilled in the art that the upper left hand quadrant of FIG. 2 (components  12 ,  16 ,  30 ,  32 ) is substantially equivalent to the switch array illustrated in FIG. 1. In the FIG. 2 expanded array, each of four plane 16×16 OSMs  30  and  32  are connected on all four sides, utilizing their full capacities. OSM  30  is thus, in addition to transmission link  22   a  from OSM  12  and transmission link  24   a,  connected to OSM  36  by transmission link  42   a  and to OSM  50  by transmission link  54   a.  Similarly, OSM  32  is connected to OSM  38  by transmission link  42   b  and to OSM  52  by transmission link  54   b.    
         [0015]    In the assembled switch array of FIG. 2 a first OSM loop is formed by OSM  30  connected to OSM  36  connected to OSM  44  connected to OSM  50  as a drop signal sorting circuit. A second OSM loop is formed by OSM  32  connected to OSM  38  connected to OSM  46  connected to OSM  52  as an add signal sorting circuit. In this arrangement, while OSM  30  and OSM  32  are presented as four plane, OSM  44  and OSM  46  have two planes each and OSMs  36 ,  38 ,  50  and  52  each have three planes. The functions of each of the OSM units is similar to that described in respect to FIG. 1 above. In addition to the add/drop terminals  14  and  18  of optical switches  12  and  16 , respectively, add/drop terminals  68  and  70  emanate from OSMs  64  and  66 , respectively.  
         [0016]    Referring now to FIG. 3, an optical switch module as a relay junction for controlling and directing optical signals is illustrated. The illustrated optical switch module is comprised, in its simplest form, of a first 8×8 three-plane micro electronic mechanical system (MEMS) switch  72  and a second three-plane MEMS switch  90  that are connected respectively to the input and output of an 8×8 two-plane MEMS switch  82 . A two-plane MEMS, such as MEMS  82 , receives an optical signal at one of its plural input ports on input plane g and routes the signal to a selected output port on output plane h, according to output port availability. A three-plane MEMS, such as MEMS  72 , receives an optical signal at one of its plural input ports on input plane a and routes the signal to a selected drop port on plane c, or passes the signal through to a corresponding output port on output plane b, as indicated in the packet header information. A four-plane MEMS, for example MEMS  30  of FIG. 2 and MEMS  72  of FIG. 4, performs similarly to three-plane MEMS, with two planes of input ports and two planes of output ports. First 8×8 MEMS switch  72  receives two sets of transmitted communication input signals at wavelengths λ 1 -λ 8 , noted as signals  74 . MEMS switch  72  is controlled so as to direct a selected input signal  74  to either of transmission output  78  that serves as input to MEMS switch  82  or drop lines  76  P- 1  through P- 8 . Drop lines  76  P- 1  through P- 8  are connected externally to packet switches for transmitting signals to a recipient client application (not shown). MEMS switch  82  operates to transmit signals  78  via signals  84  to MEMS switch  90 , and has the capability of altering the transmission channel allocation and the signal wavelength at the same time in order to allocate available output channels from MEMS switch  90 . MEMS switch  90  is connected to receive add lines  92  signals P- 1  through P- 8  from system external packet switches (not shown). The net signals of input signals  74  minus dropped signals  76  plus added signals  92  is transmitted output signals  94 , shown in wavelengths λ 1 -λ 8  to a further relay module.  
         [0017]    In keeping with the principle of growability of the present invention, a switch array is illustrated in FIG. 4 that provides an expanded version of the switch array shown in FIG. 3. Input transmission signals  96   a  and  96   b,  each being in sets of wavelengths λ 1 - 8  and λ 9 - 16 , respectively, are fed to MEMS switch  72   a  and MEMS switch  72   c,  which are each connected to MEMS switch  72   b  and  72   d,  respectively. It is readily seen that MEMS switches  72   a - 72   b - 72   c - 72   d  are operable as a three plane unit having sixteen ports on each plane. This MEMS switch unit is connected to MEMS switches  82   a  and  82   b  which then connect to MEMS switches  82   c  and  82   d,  forming an equivalent of a two plane MEMS switch with increased capacity. MEMS switches  82   c  and  82   d  transmit to MEMS switches  90   b  and  90   d  which transmit to MEMS switches  90   a  and  90   c  respectively. Therefore, the complex switch array of FIG. 4 represents a larger capacity version of the switch array of FIG. 3. Output signals  98   a  and  98   b  transmit signals out from MEMS switch unit  90   a - 90   b - 90   c - 90   d  with signal wavelengths λ 1 -λ 16 . In addition to input signals  96   a,    96   b  and output signals  98   a,    98   b,  add signals  102   a,    102   b  are connected to switches  90   c  and  90   d,  and drop signals  104   a,    104   b  are connected to transmit signals from switches  72   a  and  72   b.  Thus, while the switch array of FIG. 4 assembles 8×8 MEMS switches to result in a 32×32 array, increase of the module size to 16×16 would therefore result in a 64×64 array.  
         [0018]    While the present invention is described with respect to specific embodiments thereof, it is recognized that various modifications and variations may be made without departing from the scope and spirit of the invention, which is more clearly and precisely defined by reference to the claims appended hereto.