Optical fiber displacement sensor based on Stokes Raman backscattering light bending loss

Abstract

Optical fiber displacement sensor has the advantages of high sensitivity, large dynamic range, long sensing distance and high electromagnetic interference resistance, which has been widely used in many industrial and civil fields. However, multi-parameter simultaneous sensing is the common requirement in many applications. In this paper, we demonstrated a novel and simple optical fiber displacement sensor based on the principle of Stokes Raman backscattering, and the Stokes Raman signal is used to sense the bending loss of the sensing fiber. An optical fiber displacement sensing system and a recoverable displacement sensor is designed and built to measure the optical power loss, which makes it possible to detect the temperature and displacement simultaneously use one optical fiber. The displacement measurement is carried out for five times at 0.25 mm intervals in the range of 0–5 mm, and the experimental results show that there is a good linearity between measured and applied displacement. Its measurement accuracy is 0.1 mm and maximum sensitivity is 0.343 dB/mm. This sensor has the potential to be applied in foundation settlement monitoring, safety pre-warning of subway on-site, soil deformation measurement, and civil structure crack monitoring.