Patent ID: 6262820
Filing Date: 2001-07-17
Classification: H04J,H04Q

Abstract:
An optical node for use in an optical transmission system including a plurality of optical nodes connected by at least two optical transmission media in an optical transmission ring configuration, the at least two optical transmission media providing active optical service transmission capacity and standby optical protection transmission capacity, the node comprising:a controllable optical switch matrix having a first predetermined number of possible optical switching states and being responsive to control signals for controllably switching optical signals between the optical service capacity and optical protection capacity of said at least two optical transmission, said optical switch matrix having a plurality of optical input ports and a plurality of optical output ports, a number of said optical input ports and said optical output ports being associated with providing the active optical service transmission capacity and a number of others of said optical input ports and optical output ports being associated with providing the standby optical protection capacity;an optical detector for detecting loss of optical signal at one of more of said optical switch matrix optical input ports associated with providing the active optical service transmission capacity and for generating an indication of such loss of optical signal, and for detecting the presence of an optical signal on said optical switch matrix input ports associated with providing the optical protection transmission capacity and for generating an indication of the presence of an optical signal on an optical input port associated with providing the optical protection transmission capacity;a first timer responsive to said loss of signal indication for initiating timing of a first predetermined time interval;a second timer responsive to said signal present indication for initiating timing of a second predetermined time interval; anda controller responsive to an indication of expiration of said first time interval for generating control signals to be supplied to said optical switch matrix for causing said optical switch matrix to switch switching states so that a copy of an optical signal intended to be transmitted on said active optical service transmission capacity in a direction toward the direction of the detected loss of optical signal is transmitted on said protection transmission capacity in a direction away from the direction of the detected loss of optical signal, and being responsive to an indication of expiration of said second time interval for generating control signal to cause said optical switch matrix to switch states so the said detected optical signal is supplied as an output to terminal equipment associated with the node.