Improvement of Reliability to the Network Composed of Optical fibers inside Sewerage Pipe

The sewer system in Tokyo covers 100 % of the 23-wards area and Bureau of Sewerage, Tokyo Metropolitan Government entered its maintenance management era. We have been integrating operations of pumping stations and water reclamation plants by a remote-control system, so security and reliability of our facilities and back ground systems became a matter of great importance. We lay optical fiber cable inside trunk sewers and it is used as information infrastructure for telecommunication of remote control and our office management (internet, e-mail and so on). In this thesis, we introduce how we use our optical fiber network infrastructure which is constructed in trunk sewers and demonstrate our measures to raise its long-lasting reliability constantly including backup for disconnection fault.