Patent ID: 7747164

Claim:
A wavelength division multiplexing transmission system comprising: input/output terminal stations comprising an input/output means for inputting and outputting an optical signal and a wavelength division multiplexing transmission apparatus connected to said input/output means; an intermediate station located between said terminal stations and connected to the terminal stations through an optical transmission line for performing wavelength division multiplexing and transmission of said optical signal, a signal transmission system comprising said terminal stations and said intermediate station having a redundant configuration comprising an active system and a standby system; and a control unit which is disposed on a side of the active system and coupled to the input/output means through an intra-apparatus control bus and controls a clock synchronization of optical signal transmission on at least one of said active system and said standby system, based on control information determined for the wavelength division multiplexing transmission apparatus, wherein said input/output means for the optical signal is provided on said active system and said standby system, on a side of said active system of said terminal stations.