Temperature and Crack Measurement Using Distributed Optic-Fiber Sensor Based on Raman Loop Configuration and Fiber Loss

Abstract

In recent years, optic-fiber sensors have been required to simultaneously measure the structure's crack and environmental temperature in the infrastructure monitoring system. We proposed and experimentally demonstrated a distributed optic-fiber sensor based on the Raman loop configuration and fiber loss characteristic for detecting the temperature and structure's crack. Among them, the Raman loop configuration with reference fiber is proposed to detect the temperature profile along the sensing fiber. It can eliminate the influence of external physical perturbation on the temperature measurement results, and do not require pre-calibration process before measurement. The temperature experimental results show that the temperature accuracy and spatial resolution can reach up to 0.28°C and 1.2 m with the response time of 1.04 s. In addition, the information of crack is extracted by using the loss characteristics of Stokes, which is based on optical time domain reflectometry. The experiment results indicate that the fiber loss coefficient keeps a good linear variation between the crack ranges of 1.6 mm and 5.6 mm. The studies achieve the temperature and crack measurement only by one fiber.

Physics and applications of Raman distributed optical fiber sensing

“…In this case, development of a dual-parameter detection scheme based on a single optical fiber becomes an important technical problem for Raman distributed optical fiber sensing. For the purpose of solving the above-mentioned problems, researchers have proposed a variety of advanced solutions 26 , 134 – 138 , which are as follows.…”

“…In 2019, Li and Zhang et al demonstrated a novel dual-parameter optical fiber sensing scheme based on Stokes optical loss and the Raman effect to measure the distributed temperature and structural cracks 26 . The scheme was based on the double-end loop configuration and Stokes optical loss to extract the distributed temperature and crack information along the fiber-line.…”

“…Brillouin optical fiber sensing can measure the temperature and strain distribution along the optical fiber 20 – 24 , and can obtain a high spatial resolution for long sensing distances. Raman optical fiber sensing can monitor a large-scale distributed temperature 25 , 26 . Compared to Brillouin scattering, the Raman scattering measurement system is not sensitive to strain, so there is no cross-sensitivity of temperature and strain information in it.…”

“…Compared to Brillouin scattering, the Raman scattering measurement system is not sensitive to strain, so there is no cross-sensitivity of temperature and strain information in it. However, owing to their fast measurement speed relative to other optical fiber sensors, and structural simplicity 26 , 27 , the Raman scattering sensors are receiving extensive attention 28 – 36 .…”

Research on an Improved Metal Surface Defect Detection Sensor Based on a 3D RFID Tag Antenna

“…SHM is achieved by nondestructive testing methods without damaging the components being inspected, in industry, such as common visual inspection [4], ultrasonic inspection [5], eddy current inspection [6], and fiber optic inspection [7]. Visual inspection is a method by which a person periodically detects the degree of structural damage using auxiliary equipment [8], which has high labor costs, low detection efficiency, and environmental constraints.…”