Side-Polished Fiber-Based Hydraulic Sensing with Distributed Polarization
In this study,we develop a hydraulic sensing system employing a side-polished fiber(SPF)as the sensing medium.By side-polishing an ordinary single-mode fiber(SMF),birefringence is induced,thus resulting in a sensing unit whose fiber birefringence changes with the liquid depth.The polarization-analyzing optical-frequency-domain reflectometry technique is utilized to detect the Rayleigh backscattering light from the fiber.Signal demodulation is performed using a full-Mueller matrix-based distributed-polarization analysis method,thus enabling highly sensitive and spatially resolved birefringence measurements.Ultimately,the correlation between hydraulic pressure and fiber birefringence is established.The results show a linear correlation between the depth of side-polishing on the fiber and the induced birefringence.Moreover,with increasing hydrostatic pressure,the birefringence of the fiber sensing unit first decreases and then increases.The sensitivities for the decrease and increase in birefringence are-1.34×10-8 and 1.39×10-8 refractive index unit RIU/kPa(RIU is a unit of refractive index)for a fiber polishing depth of 40 μm.The technique proposes herein offered the possibility of achieving simultaneous multipoint hydraulic pressure sensing and presents a novel approach to implementing distributed/quasi-distributed hydraulic fiber optic sensing.
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