Hybrid Distributed Optical Fiber Sensor for the Multi-Parameter Measurements

Abstract

Distributed optical fiber sensors (DOFSs) are a promising technology for their unique advantage of long-distance distributed measurements in industrial applications. In recent years, modern industrial monitoring has called for comprehensive multi-parameter measurements to accurately identify fault events. The hybrid DOFS technology, which combines the Rayleigh, Brillouin, and Raman scattering mechanisms and integrates multiple DOFS systems in a single configuration, has attracted growing attention and has been developed rapidly. Compared to a single DOFS system, the multi-parameter measurements based on hybrid DOFS offer multidimensional valuable information to prevent misjudgments and false alarms. The highly integrated sensing structure enables more efficient and cost-effective monitoring in engineering. This review highlights the latest progress of the hybrid DOFS technology for multi-parameter measurements. The basic principles of the light-scattering-based DOFSs are initially introduced, and then the methods and sensing performances of various techniques are successively described. The challenges and prospects of the hybrid DOFS technology are discussed in the end, aiming to pave the way for a vaster range of applications.

Keywords: Brillouin scattering; Raman scattering; Rayleigh scattering; distributed acoustic sensing; distributed optical fiber sensor; distributed temperature sensing; distributed vibration sensing; multi-parameter measurements; optical time domain reflectometry.

Figure 1

The basic configuration of OTDR. DAQ: data-acquisition card.

Figure 2

The basic configuration of COTDR.

Figure 3

The typical configuration of BOTDR with coherent detection. EOM: electro-optic modulator; EDFA: erbium-doped optical fiber amplifier.

Figure 4

The typical configuration of BOTDA. ISO: isolator.

Figure 5

The typical configuration of ROTDR. WDM: wavelength-division multiplexer; APD: avalanche photodiode.

Figure 6

(a) Diagram of the frequency-scanning pump pulses and the probe wave. (b) Frequency relationship between the Rayleigh and the Brillouin scattering signals (reprinted from [199], under the terms and conditions of the Creative Commons Attribution License).

Figure 7

Experimental setup of the hybrid Φ-OTDR/BOTDA system (reprinted from [199], under the terms and conditions of the Creative Commons Attribution License).

Figure 8

Experimental setup of the hybrid Φ-OTDR/BOTDA system (reprinted from [192], under the Open Access Publishing Agreement from © 2021 Optical Society of America).

Figure 9

(a) Experimental setup of the hybrid Φ-OTDR/BOTDR system. (b) Modulated pulse sequences and the corresponding acquired signals (reprinted from [193], under the Open Access Publishing Agreement from © 2016 Optical Society of America).

Figure 10

Experimental setup of the hybrid Φ-OTDR/BOTDR system (reprinted from [145], under the Open Access Publishing Agreement from © 2022 Optica Publishing Group).

Figure 11

Experimental setup of the hybrid Φ-OTDR/BOTDA system through space-division multiplexing (SDM) based on the multi-core fiber (MCF) (reprinted from [200], under the Open Access Publishing Agreement from © 2017 Optical Society of America).

Figure 12

Experimental setup of the hybrid Φ-OTDR/BOTDA system combining multiplexing and distributed amplification techniques (reprinted from [194], under the terms and conditions of the Creative Commons Attribution License).

Figure 13

Experimental setup of the hybrid single-end-access BOTDA and COTDR system (reprinted from [195] with permission, © 2013 IEEE).

Figure 14

Experimental setup of the hybrid BOTDA/COTDR system (adapted from [197]).

Figure 15

Experimental setup of the hybrid Rayleigh and Brillouin system (reprinted from [172], under the Open Access Publishing Agreement from © 2023 Optica Publishing Group).

Figure 16

(a) Experimental setup of the hybrid BOTDR/COTDR system; (b) schematic representation of the detecting signal spectrum according to the temperature or strain change (adapted from [198]).

Figure 17

Experimental setup of the hybrid Φ-OTDR/ROTDR system using a commercial off-the-shelf DFB laser and direct detection (reprinted from [205] with permission, © 2016 Optical Society of America).

Figure 18

Experimental setup of the hybrid Φ-OTDR/ROTDR system (reprinted from [206] with permission, © 2018 Elsevier).

Figure 19

Experimental setup of the hybrid Φ-OTDR/ROTDR system based on multi-core fiber (adapted from [208]).

Figure 20

Experimental setup of the hybrid BOTDA/ROTDR system using cyclic pulse coding (reprinted from [210] with permission, © 2013 Optical Society of America).

Figure 21

Experimental setup of the hybrid BOTDR/ROTDR system based on multi-core fiber (reprinted from [212], under the Open Access Publishing Agreement from © 2016 Optical Society of America).

Figure 22

Experimental setup of the hybrid BOTDR/POTDR system (adapted from [213]).

Figure 23

Experimental setup of the frequency-scanning Φ-OTDR (reprinted from [214] with permission, © 2015 IEEE).

Figure 24

Experimental setup of the single-end hybrid Φ-OTDR/BOTDA system (adapted from [215]).

Figure 25

(a) BFS profiles when the fiber end is heated; (b) temperature evolution over the heated section; (c) vibration measured by BOTDA; (d) vibration measured by Φ-OTDR (reprinted from [192], under the Open Access Publishing Agreement from © 2021 Optical Society of America).

Figure 26

(a) Fiber arrangement in the test; (b) demodulated phase signal corresponding to an 800 Hz triangular vibration; (c) enlarged view of the hotspot at different heated temperatures (reprinted from [145], under the Open Access Publishing Agreement from © 2022 Optical Society of America).

Figure 27

(a) BFS profiles along the whole fiber; (b) BFS profiles around the heated section; (c) demodulated Rayleigh signal along the whole fiber; (d) demodulated Rayleigh signal at the location of perturbation (reprinted from [194], under the terms and conditions of the Creative Commons Attribution License).

Figure 28

(a) Total of 885 superposed consecutive differential Φ-OTDR traces with intrusion applied to two fiber segments; (b) resolved temperature distribution with denoising method (adapted from [208], detailed curves are available in the reference paper).

Figure 29

(a) Measured Raman Stokes and anti-Stokes traces along the whole fiber under various temperatures; (b) temperature distribution near the heated fiber section (reprinted from [206] with permission, © 2018 Elsevier).

Figure 30

(a) Detected vibration waterfall regarding the knock event; (b) demodulated dynamic strain corresponding to the vibration exerting on the PZT; (c) frequency responses of the demodulated dynamic strain with different frequencies (reprinted from [206] with permission, © 2018 Elsevier).

Figure 31

(a) Diagram of the test bench for independent measurement of temperature and strain; (b) independent measurement of distributed temperature and strain (adapted from [198], detailed curves are available in the reference paper).

Figure 32

(a) Diagram of the good instrumentation for a distributed measurement of temperature and strain; (b) comparative curves of a distributed measurement among BOTDR DSTS (blue curve for temperature and purple curve for strain), standard ROTDR (red curve) and standalone BOTDR (yellow curve) (adapted from [198], detailed curves are available in the reference paper).

Figure 33

(a) Recovered temperature variation over time; (b) recovered strain variation over time; (c) amplitude spectral density curve of the recovered temperature; (d) amplitude spectral density curve of the recovered strain (reprinted from [172], under the Open Access Publishing Agreement from © 2023 Optica Publishing Group).

Figure 34

(a) Temperature distribution measured by Raman scattering; (b) strain resolution along the sensing fiber (reprinted from [210] with permission, © 2013 Optical Society of America).

Figure 35

(a) Absolute temperature distribution measured by BOTDA; (b) relative temperature distribution measured by Φ-OTDR; (c) estimated temperature uncertainty distribution of BOTDA; (d) estimated temperature uncertainty distribution of Φ-OTDR (reprinted from [200], under the Open Access Publishing Agreement from © 2017 Optical Society of America).

Figure 36

(a) Absolute strain change measured by BOTDA; (b) relative strain change of group 1 measured by Φ-OTDR; (c) relative strain change of group 2 measured by Φ-OTDR (reprinted from [199], under the terms and conditions of the Creative Commons Attribution License).