Long Range Raman-Amplified Distributed Acoustic Sensor Based on Spontaneous Brillouin Scattering for Large Strain Sensing.

Shahab Bakhtiari Gorajoobi,Ali Masoudi,Gilberto Brambilla

doi:10.3390/s22052047

Shahab Bakhtiari Gorajoobi, Ali Masoudi + Show 1 more

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https://doi.org/10.3390/s22052047

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Journal: Sensors (Basel, Switzerland)	Publication Date: Mar 6, 2022
Citations: 1	License type: CC BY 4.0

Affiliation: University of Southampton

Abstract

A Brillouin distributed acoustic sensor (DAS) based on optical time-domain refractometry exhibiting a maximum detectible strain of 8.7 m and a low signal fading is developed. Strain waves with frequencies of up to 120 Hz are measured with an accuracy of 12 at a sampling rate of 1.2 kHz and a spatial resolution of 4 m over a sensing range of 8.5 km. The sensing range is further extended by using a modified inline Raman amplifier configuration. Using 80 ns Raman pump pulses, the signal-to-noise ratio is improved by 3.5 dB, while the accuracy of the measurement is enhanced by a factor of 2.5 to 62 at the far-end of a 20 km fiber.

Highlights

High sensitivity and long sensing range of Distributed Acoustic Sensors (DASs) have made them ideal devices for sensing vibrations of elongated structures such as pipelines, railways, and subsea cables [1–6]
Since the strain measurement in based DAS (B-DAS) systems is based on the changes of the Brillouin Frequency Shift (BFS), B-DAS systems have no limitation in detecting large strain variations so far as they can acquire the Brillouin Gain Spectrum (BGS) at each point on the sensing fiber fast enough
The proposed method provides a sensing system based on interferometric demodulation which does not suffer from intensity fading and does not require any locking mechanism associated with other types of B-DASs [29–31]

Summary

Introduction

High sensitivity and long sensing range of Distributed Acoustic Sensors (DASs) have made them ideal devices for sensing vibrations of elongated structures such as pipelines, railways, and subsea cables [1–6]. This limitation restricts the use of φ-DAS in applications that require measurement of high strain-rates over long distances such as analysis of large-magnitude earthquakes or evaluation of railway track behavior [3,17]. The commonly used interrogation techniques used in B-DAS systems include Brillouin Optical Time-domain Analysis (BOTDA), Brillouin Optical Correlation-domain Analysis (BOCDA), and Brillouin Optical Time-domain Refractometry (BOTDR)

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