| 摘要 |
An optic relay unit includes (a) an excitation light source to which a predetermined inherent frequency is assigned, (b) an optical amplifier arranged in a transmission line through which a main signal light having a predetermined wavelength is transmitted, to receive the main signal light, the optical amplifier being excited by an excited light emitted from the excitation light source and amplifying the main signal light, and (c) a fault monitoring unit which generates a fault monitoring signal light modulated with the predetermined inherent frequency and having a wavelength different from the predetermined wavelength of the main signal light, when a fault occurs in the excitation light source, and transmits the fault monitoring signal light to the transmission line.
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