| 摘要 |
An optical amplifying and relaying system capable of easily and highly accurately monitor troubles in optical amplifiers provided in an up and a down optical fiber transmission line opposing each other is disclosed. Monitoring light signal folding-back lines including variable optical attenuators 4a and 4b and wavelength selective reflecting means 5a and 5b, respectively, are provided between optical transmission lines L1 and L2, which oppose each other and on which optical amplifiers 4a and 4b are disposed each other.
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