Staas & Halsey LLP
Redundant optical source switching method and wavelength division multiplexing transmission apparatus using the same
 A redundant switch method includes a step of producing a substitute light of a wavelength identical to that of a faulty working light source which is one of working light sources having different wavelengths by optical four-wave mixing using a protection light from a protection light source and a branch light which is one of branch lights obtained from the working light sources and has a given relationship with the faulty working light source. A transmission light of the faulty working light source is replaced by the substitute light. 
Fujitsu Limited
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Yasuo
Suzuki