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. 2016 Dec 16;16(12):2156.
doi: 10.3390/s16122156.

Bi-Directional Brillouin Optical Time Domain Analyzer System for Long Range Distributed Sensing

Nan Guo  1 , Liang Wang  2 , Jie Wang  3 , Chao Jin  4 , Hwa-Yaw Tam  5 , A Ping Zhang  6 , Chao Lu  7
Affiliations

Bi-Directional Brillouin Optical Time Domain Analyzer System for Long Range Distributed Sensing

Nan Guo et al. Sensors (Basel). .

Abstract

We propose and experimentally demonstrate a novel scheme of bi-directional Brillouin time domain analyzer (BD-BOTDA) to extend the sensing range. By deploying two pump-probe pairs at two different wavelengths, the Brillouin frequency shift (BFS) distribution over each half of the whole fiber can be obtained with the simultaneous detection of Brillouin signals in both channels. Compared to the conventional unidirectional BOTDA system of the same sensing range, the proposed BD-BOTDA scheme enables distributed sensing with a performance level comparable to the conventional one with half of the sensing range and a spatial resolution of 2 m, while maintaining the Brillouin signal-to-noise ratio (SNR) and the BFS uncertainty. Based on this technique, we have achieved distributed temperature sensing with a measurement range of 81.9 km fiber at a spatial resolution of 2 m and BFS uncertainty of ~0.44 MHz without introducing any complicated components or schemes.

Keywords: Brillouin scattering; fiber optics sensors; optical time domain analyzer; temperature.

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Conflict of interest statement

The authors declare no conflict of interest. The founding sponsors had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.

Figures

Figure 1
Figure 1
Principle of BD-BOTDA: two pump-probe pairs including pulsed pumps and CW probes at two wavelengths are injected into both ends of the FUT in opposite directions.
Figure 2
Figure 2
Experiment setup of BD-BOTDA system. TL: Tunable laser; PC: Polarization controller; EDFA: Erbium-doped fiber amplifier; BPF: Band pass filter; MZM: Mach–Zehnder modulator; PPG: Pulse pattern generator; PS: Polarization scrambler; VOA: Variable optical attenuator; FBG: Fiber Bragg grating; PD: Photodiode; OSC: Oscilloscope; FUT: Fiber under test.
Figure 3
Figure 3
Brillouin frequency shift versus temperature at two wavelengths: λ1 and λ2.
Figure 4
Figure 4
BGS as a function of distance measured at (a) the λ1 channel along FUT I (left) and the corresponding zoom-in view of the last 10 m of the fiber (right), and (b) the λ2 channel along FUT III (left) and the corresponding zoom-in view of the last 12 m of the fiber (right).
Figure 5
Figure 5
Temperature distribution measured with (a) the λ1 channel at the far end of its sensing fiber and (b) the λ2 channel at the far end of its sensing fiber.
Figure 6
Figure 6
Normalized Brillouin time domain trace of (a) the 40.6 km SMF measured with the unidirectional BOTDA system (left); (b) the 81.9 km SMF measured with the unidirectional BOTDA system (left); (c) the λ1 channel measured with the BD-BOTDA system (left); and (d) the λ2 channel measured with the BD-BOTDA system (left). Each trace is measured at Brillouin center frequency shift of the SMF. Insets: the contrast between the Brillouin signal near the end of the fibers (red curve) and the noise background (blue curve) on the right hand side.
Figure 7
Figure 7
BFS versus distance of (a) the 40.6 km SMF in the unidirectional BOTDA system; (b) the 81.9 km SMF in the unidirectional BOTDA system; (c) the λ1 channel in the BD-BOTDA system along FUT I; and (d) the λ2 channel in the BD-BOTDA system along FUT III.
See this image and copyright information in PMC

References

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