Recent Progress in Distributed Fiber Acoustic Sensing with Φ-OTDR

Abstract

Distributed fiber acoustic sensing (DAS) technology can continuously spatially detect disturbances along the sensing fiber over long distance in real time. It has many unique advantages, including, large coverage, high time-and-space resolution, convenient implementation, strong environment adaptability, etc. Nowadays, DAS becomes a versatile technology in many fields, such as, intrusion detection, railway transportation, seismology, structure health monitoring, etc. In this paper, the sensing principle and some common performance indexes are introduced, and a brief overview of recent DAS researches in Shanghai Institute of Optics and Fine Mechanics (SIOM) is presented. Some representative research advances are explained, including, quantitative demodulation, interference fading suppression, frequency response boost, high spatial resolution, and distributed multi-dimension localization. The engineering applications of DAS, carried out by SIOM and other groups, are summarized and reviewed. Finally, possible future directions are discussed and concluded. It is believed that, DAS has great development potential and application prospect.

Long-Range Optical Fiber Based Distributed Mechanical Vibration Sensing

“…The attenuation is caused by double attenuation both of interrogating pulses in forward direction and of backscattered signal in backward direction. Fluctuations of backscattered signal occur due to the usage of ultra-narrow laser source, random locations of scattering centers within the fiber and random phase of scattered signals that are superimposed during the path to the receiver side, [6]. As shown in Figure 5 the signal level falls close to zero level at many time instants and this deteriorates the sensor sensitivity at corresponding locations along the sensing fiber.…”

Recent Advances in Machine Learning for Fiber Optic Sensor Applications

“…The major noise sources in a Φ-OTDR system arise from two fading phenomena, namely, intensity fading and polarization fading. [40] Intensity fading can be observed as major fluctuations in Rayleigh backscattered traces, caused by the interference of backscattered Rayleigh signals from different scattered points within a pulse. Polarization fading is a major cause of concern in heterodyne detection-based Ø-OTDR systems, due to polarization mismatch between the local oscillator and the backscattered signal.…”

“…[74][75][76][77][78] 4) Deep learning algorithms: denoising convolutional neural networks. [40] With regard to long-range BOTDA applications, denoising algorithms aid in reducing the number of trace averages [72] and subsequently help in reducing BOTDA measurement time. Early work in BOTDA literature advocated for denoising based on decomposition-based (HilbertÀHuang, wavelet transform) and adaptive filtering techniques.…”

Fiber Optic Based Distributed Mechanical Vibration Sensing

“…Distributed optical fiber vibration sensors have the capability of mechanical vibrations sensing in a distributed manner, i.e., they can detect and localize many events along with the sensing fiber, simultaneously. Many techniques, measurement methods, and schemes were proposed during the last two decades [ 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 ]. The most common measurement scheme is based on the analysis of the Rayleigh backscattered signal from interrogating pulses sent to the fiber, which is similar to the reflectometry principle used in OTDR (optical time-domain reflectometry), as shown in Figure 2 .…”