FRPM Pipeline Remote Sensing by Microwave Using Radio-Over-Pipewall (RoP) and Radio-Over-Fiber (RoF) Techniques

We propose a new remote diagnostic technique using microwave time-domain response and Radio-over-fiber (RoF) technology to efficiently diagnose underground Fiberglass-Reinforced Plastic Mortar (FRPM) pipelines in a non-destructive and non-excavation scheme. We focused on the “Radio-over-Pipewall (RoP)” characteristics, in which microwaves propagate along the FRPM pipe wall and converge inside the cylindrical dielectric wall (FRPM) as guided modes, when the FRPM is buried underground to compose three layers of soil/FRPM/air. We demonstrate that this characteristic can be used to identify defects and foreign objects on or in the walls of the pipeline. In this study, we attempted to use a RoF link with a DFB laser, silica optical fiber, and photodiode to develop more advanced RoP-based diagnostic technique. Experimental results demonstrated that remote measurement is possible with the measurement equipment required for diagnosis installed at a distance (~km) from the pipe to be inspected, such as on the ground.