Polarization dependence of the noise of phase measurement based on phase-sensitive OTDR

Abstract

A phase-sensitive optical time-domain reflectometry (∅-OTDR) implements high-sensitivity vibration measurement by measuring vibration induced phase change of Rayleigh scattering from the sensing fiber. Minimum detectable vibration of a ∅-OTDR is limited by the noise of the phase measurement. In this paper, polarization dependence of the noise of phase measurement in a ∅-OTDR is investigated theoretically and experimentally. The correspondence between the intensity of Rayleigh scattering and the polarization state of the probe pulse in a ∅-OTDR is analyzed considering inner interference of coherent Rayleigh light scattered within pulse duration and polarization dependence of propagation constant. Experiments are performed and the results confirm the predictions of the theoretical analysis. This study is essential for acquiring insight into polarization dependence of vibration measurement based on a ∅-OTDR, and would provide a feasible method to eliminate the effect of polarization fading and optimize the minimum detectable vibration of a ∅-OTDR.

Blast-Assisted Subsurface Characterisation Using a Novel Distributed Acoustic Sensing Setup Based on Geometric Phases

“…This is not the case in the optical fiber medium, where after the first few meters, the SOP of the probe signal diverges from that of the LO [ 27 ]. Resulting polarization mismatches cause unwanted signal fades and are traditionally handled with polarization diversity techniques [ 28 , 29 , 30 , 31 , 32 , 33 ]. The unwanted peaks in the determined phase due to polarization mismatch fading or unwrapping errors can cause false alarms in applications like earthquake and structural health monitoring [ 34 ].…”

Multi-Event Location Denoising Scheme for φ-OTDR Based on FFDNet Network

“…Zhang et al proposed to use of three acoustic-optic modulators (AOMs) for the ϕ-OTDR system to generate three different frequencies of detection pulses, only increasing the number of AOMs without changing the conventional ϕ-OTDR structure, effectively suppressed the coherent fading and obtained a distortion-free output signal of over 98.85% [18]. Yu et al proposed a ϕ-OTDR system combining a polarization controller with a Mach-Zehnder interferometer (MZI), and the SNR of the system was improved by 15 dB compared with the original structure [19]. However, changing the system structure is quite effective for the deterministic noise existing in the system, but for the background noise with strong randomness, changing the system structure alone cannot effectively remove it.…”