Method and apparatus for detecting a fault on an optical fiber

Abstract

Mechanisms for operating a network element in an optical network are disclosed. A network element has a plurality of ports, each port including a respective receive input for receiving an optical signal from another network element and a respective transmit output for transmitting an optical signal to the other network element. Each port is configured with a respective fault detection mode of a plurality of fault detection modes. The plurality of fault detection modes include a first fault detection mode in which interruption of the optical signal received from the other network element on the respective receive input is interpreted as indicating interruption of an optical path from the respective transmit output to the other network element, and a second fault detection mode in which detection of a predetermined signal pattern from the other network element on the respective receive input is interpreted as indicating interruption of the optical path from the respective transmit output to the other network element.

What is claimed is: 
     
         1 . A method of operating a network element in an optical network, the network element having a plurality of ports, each port comprising a respective receive input for receiving an optical signal from another network element and a respective transmit output for transmitting an optical signal to the other network element, the method comprising configuring each port with a respective fault detection mode of a plurality of fault detection modes, the plurality of fault detection modes comprising:
 a first fault detection mode in which interruption of the optical signal received from the other network element on the respective receive input is interpreted as indicating interruption of an optical path from the respective transmit output to the other network element; and   a second fault detection mode in which detection of a predetermined signal pattern from the other network element on the respective receive input is interpreted as indicating interruption of the optical path from the respective transmit output to the other network element.   
     
     
         2 . The method of  claim 1 , wherein the predetermined signal pattern comprises an interruption of the optical signal from the other network element at the respective receive input persisting for a predetermined period of time. 
     
     
         3 . The method of  claim 1 , comprising monitoring a respective receive input of a respective port for the predetermined signal pattern when the respective port is operating in the second fault detection mode. 
     
     
         4 . The method of  claim 3 , comprising:
 detecting the predetermined signal pattern at the respective receive input of the respective port; and   responsive to detecting the predetermined signal pattern, determining a presence of a fault on the optical path from the respective transmit output of the respective port to the other network element.   
     
     
         5 . The method of  claim 3 , comprising:
 detecting the predetermined signal pattern at the respective receive input of the respective port; and   responsive to detecting the predetermined signal pattern, interrupting optical transmission on the respective transmit output of the respective port.   
     
     
         6 . The method of  claim 5 , wherein the predetermined signal pattern comprises intervals of optical signal interruption of a predetermined duration at the respective receive input interleaved with intervals of optical signal reception at the respective receive input. 
     
     
         7 . The method of  claim 6 , wherein detecting the predetermined signal pattern comprises detecting at least a predetermined number of intervals of optical signal interruption of the predetermined duration. 
     
     
         8 . The method of  claim 7 , wherein the at least a predetermined number of intervals of optical signal interruption of the predetermined duration is configurable. 
     
     
         9 . The method of  claim 1 , comprising interrupting optical transmission from the respective transmit output of a respective port responsive to fault detection at the respective port. 
     
     
         10 . The method of  claim 1 , comprising transmitting the predetermined signal pattern from the respective transmit output of a respective port responsive to fault detection at the respective port. 
     
     
         11 . The method of  claim 1 , comprising transmitting the predetermined signal pattern from the respective transmit output of a respective port responsive to fault detection at the respective port to signal the other network element that there is a fault in an optical path from the other network element to the respective receive input of the respective port. 
     
     
         12 . The method of  claim 1 , wherein:
 the plurality of ports comprises a plurality of distinct groups of ports; and   configuring each port with a respective fault detection mode of the plurality of fault detection modes comprises configuring each group of ports with a respective fault detection mode of the plurality of fault detection modes.   
     
     
         13 . The method of  claim 12 , wherein each group of ports is located on a respective input/output card of the network element wherein each input/output card of the network element has a respective fault detection mode. 
     
     
         14 . The method of  claim 13 , wherein the first and second optical waveguides are optical fibers. 
     
     
         15 . The method of  claim 1 , wherein each respective receive input is coupled to a first optical waveguide and each respective transmit output is coupled to a second optical waveguide. 
     
     
         16 . The method of  claim 1 , wherein:
 a transmit output of a particular port of the network element is coupled to a receive input of a particular port of the other network element via a first optical path;   a receive input of the particular port of the network element is coupled to a transmit output of the particular port of the other network element via a second optical path;   the particular port of the network element is configured with the first fault detection mode of the plurality of fault detection modes; and   the particular port of the other network element is also configured with the first fault detection mode.   
     
     
         17 . The method of  claim 16 , comprising transmitting the predetermined signal pattern from the respective transmit output of a respective port responsive to fault detection at the respective port to signal the other network element that there is a fault in an optical path from the other network element to the respective receive input of the respective port. 
     
     
         18 . The method of  claim 17 , comprising:
 detecting the predetermined signal pattern at a respective receive input of the particular port of the other network element; and   responsive to detecting the predetermined signal pattern at the receive input of the particular port of the other network element, interrupting optical transmission on the transmit output of the particular port of the other network element.   
     
     
         19 . The method of  claim 17 , comprising:
 detecting the predetermined signal pattern at a respective receive input of the particular port of the other network element; and   responsive to detecting the particular signal pattern, determining presence of a fault on the second optical path.