Few-mode optical fiber based simultaneously distributed curvature and temperature sensing

Abstract

The few-mode fiber (FMF) based Brillouin sensing operated in quasi-single mode (QSM) has been reported to achieve the distributed curvature measurement by monitoring the bend-induced strain variation. However, its practicality is limited by the inherent temperature-strain cross-sensitivity of Brillouin sensors. Here we proposed and experimentally demonstrated an approach for simultaneously distributed curvature and temperature sensing, which exploits a hybrid QSM operated Raman-Brillouin system in FMFs. Thanks to the larger spot size of the fundamental mode in the FMF, the Brillouin frequency shift change of the FMF is used for curvature estimation while the temperature variation is alleviated through Raman signals with the enhanced signal-to-noise ratio (SNR). Within 2 minutes measuring time, a 1.5 m spatial resolution is achieved along a 2 km FMF. The worst resolution of the square of fiber curvature is 0.333 cm while the temperature resolution is 1.301 °C at the end of fiber.

Review of Specialty Fiber Based Brillouin Optical Time Domain Analysis Technology

“…Since the first sensing demonstration with an SMF (BFS ~ 1.6 MHz for a 1.5 m of SMF winded around a rod of 25 mm diameter [52]), different optical fibers have been investigated. Among them, a few-mode fiber was used to improve the sensitivity (~5 time for a radius curvature of 0.8 cm) and to extend the range of curvature measurements (radius curvature from 0.7 cm to 3.4 cm) [53]. MCF was successfully used for demonstrating −1…”

“…Since the first sensing demonstration with an SMF (BFS ~1.6 MHz for a 1.5 m of SMF winded around a rod of 25 mm diameter [52]), different optical fibers have been investigated. Among them, a few-mode fiber was used to improve the sensitivity (~5 time for a radius curvature of 0.8 cm) and to extend the range of curvature measurements (radius curvature from 0.7 cm to 3.4 cm) [53]. MCF was successfully used for demonstrating curvature radius and orientation measurements (with a BFS sensitivity of 2.06 MHz/m −1 ) by correlating the difference of BFS between the central core and outer six cores, paving the way to full 3D shape determination using an optical fiber [44].…”

A Review of Using Few-Mode Fibers for Optical Sensing

“…For example, the temperature resolution along the fiber should be provided. Wu et al reported utilizing a QSM-operated FMF to design a novel Raman-Brillouin system for simultaneous distributed curvature and temperature sensing [55]. By adding a Raman filter to a conventional BOTDA setup, the authors separated the Raman and Brillouin signals, in the wavelength-domain.…”

A Brief Review of Specialty Optical Fibers for Brillouin-Scattering-Based Distributed Sensors

“…Very nice theoretical analyses of such interactions can be found in [129,130]. Xu et al [62,131] provided an analysis involving modes possessing orbital angular momentum, while Wu et al [132] described a hybrid Raman-Brillouin system in a few-mode fiber.…”