Protection of WDM-channels

摘要

An optical network comprises a bidirectional link connecting two nodes ( 1 ) through two optical fibers ( 3 ). Optical output signals from optical transmitters ( 7 ) in a node are provided to transponders ( 11 ) issuing optical signals of well-defined wavelengths to a power combiner ( 13 ), from which optical signals are forwarded to the other node on the respective fiber. The network can have protection for failures of various components. Thus, a spare transponder ( 21 ) can receive the optical output signals of an optical transmitter ( 7 ) in the case of a failure of an ordinary transponder ( 11 ). The spare transponder ( 21 ) is also connected to the combiner ( 13 ). The optical transmitters ( 7 ) and receivers ( 9 ) can be duplicated by providing spare transmitters ( 7 ') and spare receivers ( 9 '). Various arrangements can be used for connecting the output of a transmitter to an ordinary transponder or the spare transponder. For example, cross-bar switches ( 17, 19 ) can be arranged at the outputs of a pair of an ordinary transmitter and a spare transmitter and at the inputs of a pair of an ordinary receiver and a spare receiver. For a node having N-1 ordinary transmitters a N:1 switch ( 23 ) is then arranged at the input of the spare transponder ( 21 ).