Crosspoint switch protection

Abstract

A crosspoint switch is described that has N inputs, M outputs and an array of (N+X)×(M+X), where N M and X are all positive integers. By providing more than the standard N×M switching elements, it becomes possible to utilise the additional switching elements to provide one or more additional protection pathways to compensate for a failure in a switching element.

1 . A crosspoint switch comprising N inputs, M outputs and an array of (N+X)×(M+X) switching elements, where M, N and X are all positive integers, the additional switching elements in said array being arranged to provide alternative connectivity between said inputs and outputs.  
     
     
         2 . A crosspoint switch as claimed in  claim 1 , wherein said switch is a photonic switch.  
     
     
         3 . A switch as claimed in  claim 1 , wherein said additional switching elements comprise at least one column at an outermost edge of the array, and at least one row at an outermost edge of the array.  
     
     
         4 . A switch as claimed in  claim 3 , wherein the additional switching element located at an intersection of said row and said column is located in a fixed position so as to redirect incident signals in a predetermined manner.  
     
     
         5 . A switch as claimed in  claim 1 , further comprising X additional inputs and X additional outputs, each of said additional outputs being transmissively connected to a respective additional input.  
     
     
         6 . A switch as claimed in  claim 5 , wherein said switch is a photonic switch, and said additional outputs are connected to said additional inputs by an optical wave guide.  
     
     
         7 . A switch as claimed in  claim 5 , wherein at least one of said additional outputs is coupled to a tap for the monitoring of signals passing through said output.  
     
     
         8 . A switch as claimed in  claim 1 , wherein N=M.  
     
     
         9 . A switch as claimed in  claim 1 , wherein X=2.  
     
     
         10 . A switch as claimed in  claim 1 , wherein said array is substantially rectilinear.  
     
     
         11 . A node for a telecommunications network comprising a crosspoint switch comprising N inputs, M outputs and an array of (N+X)×(M+X) switching elements, where M, N and X are all positive integers, the additional switching elements in said array being arranged to provide alternative connectivity between said inputs and outputs.  
     
     
         12 . A transmission system comprising a transmitter and a receiver, and a transmission line connecting the transmitter to the receiver, the system further comprising a crosspoint switch comprising N inputs, M outputs and an array of (N+X)×(M+X) switching elements, where M, N and X are all positive integers, the additional switching elements in said array being arranged to provide alternative connectivity between said inputs and outputs.  
     
     
         13 . A method of operating a crosspoint switch comprising N inputs, M outputs and an array of (N+X)×(M+X) switching elements, where N, M and X are all positive integers, the method comprising 
 detecting that switching element has seized to function correctly; and  
 providing control signals to the switching elements for configuring the switching elements to provide the same connectivity as the incorrectly functioning switching element.  
 
     
     
         14 . A method as claimed in  claim 13 , wherein said switch is a photonic switch arranged to switch optical signals, the method further including the step of providing control signals to the switching elements for configuring the switching elements so as to ensure that no optical signals are blocked by the incorrectly functioning switching element.  
     
     
         15 . A computer program arranged to perform the method of a method of operating a crosspoint switch comprising N inputs, M outputs and an array of (N+X)×(M+X) switching elements, where N, M and X are all positive integers, the method comprising 
 detecting that switching element has seized to function correctly; and  
 providing control signals to the switching elements for configuring the switching elements to provide the same connectivity as the incorrectly functioning switching element.  
 
     
     
         16 . A computer program as claimed in  claim 15 , wherein said computer program is stored on a machine readable medium.