OTDR Based Fiber Optic Microbend Sensor for Distributed Sensing Applications in Structural Pressure Monitoring

The ability to understand and monitor the distributed behaviour of extended, critical structures is recognized as a matter of increasing importance. Optical fibres offer unique advantages for spatially distributed measurement. An especially important feature is the one dimensional nature of the medium, since this offers unique advantages for spatially distributed measurement. This article describes the principle of operation, the design and performance of a novel single mode fiber based multipoint microbend pressure sensor architecture, which may be utilized in distributed measurement. The actual sensor element is a single mode fiber coupled to the measurand field through the usual microbend inducing structures. The sensor uses optical time domain reflectometry (OTDR) to detect pressure induced charges of backscatter power at many separate locations in the fiber as a function of length along a single fiber with no taps or branches. The sensitivity of this structure to microbend induced losses has been thoroughly characterized. This feature greatly increases the information from a single instrument and hence decreases the cost-benefit ratio.