Dual pulse heterodyne distributed acoustic sensor system employing SOA-based fiber ring laser

Abstract

Distributed Acoustic Sensor (DAS) has potential in applications such as hydroacoustic detection. In this paper, a dual-pulse heterodyne distributed acoustic sensor (DAS) system using a semiconductor optical amplifier (SOA)-based fiber ring laser (FRL) is proposed. Unlike the previous DAS system configurations, the SOA-based FRL replaces the narrow linewidth laser (NLL) and pulse modulator, reducing costs and simplifying the system. The system is demonstrated theoretically and validated experimentally. The adaptability of the SOA-based FRL in the heterodyne DAS system has been demonstrated in the experiments. Using the dual-pulse heterodyne detection method, the sensor system responds well to distributed acoustic detection and achieves accurate demodulation and positioning. A high signal-to-noise ratio (SNR) of 42.51 dB at 3 kHz is demonstrated as a demodulation result. The system’s frequency range is 5 Hz to 5 kHz with a spatial resolution of 12 m. The proposed approach shows a broad application prospect for low-cost, large-scale, high-SNR distributed acoustic detection in maritime surveillance.

Dynamic range extension for heterodyne fibre‐optic hydrophone by using instantaneous frequency‐tracking method

“…The IF can provide information about the demodulated rotation directions. For an acoustic introduced phase signal φ t = A sig sin (2π f sig t ), IFs f inst ( t ) can be written as follows[9, 12]: $$$$\begin{equation} \def\eqcellsep{&}\begin{array}{*{20}{c}} {{f_{inst}}\ \left( t \right) = {f_c}\ + \frac{1}{{2\pi }}\ \frac{{d{\varphi _t}}}{{dt}} = {f_c}\ + {A_{sig}}{f_{sig}}\cos \left( {2\pi {f_{sig}}t} \right)} \end{array} \end{equation}$$$$…”

“…Various signal detection schemes and corresponding optimization methods have been investigated [3][4][5][6]. Among these, heterodyne detection techniques have received attention and research, showing excellent performance in the dynamic range [7][8][9]. Still, some applications require a dynamic range beyond the existing signal detection techniques [10].…”

“…For the commonly used IQ quadrature demodulation algorithm [9], when the phase of successive sampling points exceeds ± π , the demodulator undergoes a significant phase wrapping [17]. To overcome the phase wrapping, the adopted IF-tracking method is added after the algorithm to correct the phase distortion, as shown in Figure 3.…”

“…The IF can provide information about the demodulated rotation directions. For an acoustic introduced phase signal ϕ t = A sig sin (2π f sig t), IFs f inst (t) can be written as follows [9,12]:…”

Research on the intrinsic phase difference of Rayleigh scattering in distributed acoustic sensing

“…Zhang et al introduced a DAS system based on a semiconductor optical amplifier (SOA) with a double-pulse outlier detection method for precise demodulation and localization. This system offers a frequency range of 5 Hz-5 kHz and achieves a spatial resolution of 12 meters [8]. Masoudi and Newson employed a φ-optical time domain reflectometry (OTDR) detection technique with an enhanced optical setup and a novel signal processing program to achieve measurements with a frequency resolution of up to 5 Hz and a spatial resolution of 50 cm [9].…”