| 摘要 |
PROBLEM TO BE SOLVED: To efficiently automatic switching/switching-back operation at low cost with high precision in case of a fault due to the simple redundant constitution of the light source. SOLUTION: An alternative light λyi having the same wavelength with an in-use light source (λxi) having got out of order is generated by the four-light- wave mixing of one branch light λxj in specific relation with an arbitrary active light source 11i (λxi) having arbitrary got out of order among branch lights of active light sources 111 to 11n having different wavelengths λx1 to λxn and the light λp of a standby light source 52, and the transmit light λxi of the active light source having got out of order is switched to the alternative light λyi. Preferably, the branch light λp of the standby light source 52 is used for a standby communication channel of one of transmission sections and once a fault occurring to the active channel of one of the transmission sections is detected, the main signal of the faulty channel is sent with the branch light λp of the standby light source instead. |
