Temperature-strain discrimination in distributed optical fiber sensing using phase-sensitive optical time-domain reflectometry

Abstract

A method based on coherent Rayleigh scattering distinctly evaluating temperature and strain is proposed and experimentally demonstrated for distributed optical fiber sensing. Combining conventional phase-sensitive optical time-domain domain reflectometry (ϕOTDR) and ϕOTDR-based birefringence measurements, independent distributed temperature and strain profiles are obtained along a polarization-maintaining fiber. A theoretical analysis, supported by experimental data, indicates that the proposed system for temperature-strain discrimination is intrinsically better conditioned than an equivalent existing approach that combines classical Brillouin sensing with Brillouin dynamic gratings. This is due to the higher sensitivity of coherent Rayleigh scatting compared to Brillouin scattering, thus offering better performance and lower temperature-strain uncertainties in the discrimination. Compared to the Brillouin-based approach, the ϕOTDR-based system here proposed requires access to only one fiber-end, and a much simpler experimental layout. Experimental results validate the full discrimination of temperature and strain along a 100 m-long elliptical-core polarization-maintaining fiber with measurement uncertainties of ~40 mK and ~0.5 με, respectively. These values agree very well with the theoretically expected measurand resolutions.

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“…The two tones were amplified by an erbium-doped fiber amplifier (EDFA), and then amplitude- The magnitude of Rayleigh back-scatter of coherent optical fields is extremely noisy [34,35].…”

Design of Polarization Splitter via Liquid and Ti Infiltrated Photonic Crystal Fiber

“…The polarization handling devices based on PCFs filled with material, such as polarization splitters (PS) [20][21][22] and polarization rotators (PR) [23,24], have important applications in optical fiber sensing [25,26]. The PS could be divided into two fundamental modes (HE x 11 and HE y 11 ) and propagate them in different directions.…”

Preliminary Study of Distributed Fiber Optic Sensing Technologies in Hydraulic Machinery

“…DOFS can provide physical information continuously all along the entire optical fiber length. The DOFS for short range and high resolution strain monitoring include optical time domain reflectometry (OTDR) [5], [6] and optical frequency domain reflectometry (φOFDR) [7], based on Rayleigh scattering induced by the refractive index inhomogeneity in optical fiber, and the measured position distance L to the detector is deduced by the travelling time of back scattered pulses τ in the optical fiber, τ=2nL/c, where n is the refractive index of the fiber and c is the light velocity in vacuum [8]. Table 1 shows a rough comparison of various parameters of the different DOFS.…”