Quasi-distributed displacement sensor for structural monitoring using a commercial OTDR

A quasi-distributed displacement sensor for structural monitoring using an optical time domain reflectometer is demonstrated. Four displacement sensing heads are placed along a standard single mode optical fibre in several locations with different intervals. Their configurations introduce power loss through the decrease of their fibre loop radius when displacement is applied. The decrease of the light intensity with displacement variation is reported. Losses of 9 dB for a ∼120 mm displacement with a sensitivity of ∼0.027 dB/mm are reported. The quasi-distributed configuration is able to address sensors with ∼1 m distance resolution between them.