Design and investigation of a novel optic fiber sensor based on OTDR for land subsidence monitoring

Abstract

The paper presents an innovative fiber optic displacement sensor with a wide and linear measurement range, which capitalizes on the principle of macro-bending loss. The sensor incorporates a single optical fiber that is spirally wound around a non-standard spring, creating a unique sensing element. It functions in tandem with a standard spring, connected in series. The working mechanism of the sensor is thoroughly explained, and a corresponding mathematical model has been developed. An in-depth experimental analysis of the sensor’s performance has been conducted. The findings indicate a strong linear correlation between the displacement measurements and the macro-bending loss of the optical fiber. It boasts a substantial measurement range of 90 mm, with a minimal displacement resolution of 0.150 mm. The sensor also exhibits a maximum hysteresis error of 4.81 % and a maximum repeatability error of 8.62 %. Additionally, a soil drainage model test utilizing two of these sensors to assess their capability in detecting soil compression deformation was performed in details. The experimental results underscore the potential of these sensors to be interconnected on a single optical link, enabling quasi-distributed sensing monitoring. This research paves the way for the promising application of such sensors in real-time monitoring of soil settlement deformation and related phenomena.