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A Cost-Effective Distributed Acoustic Sensor Using a Commercial Off-the-Shelf DFB Laser and Direct Detection Phase-OTDR | IEEE Journals & Magazine | IEEE Xplore

A Cost-Effective Distributed Acoustic Sensor Using a Commercial Off-the-Shelf DFB Laser and Direct Detection Phase-OTDR

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A cost-effective distributed acoustic sensor using a commercial off-the-shelf DFB laser and direct detection phase-OTDR.
Impact Statement:For the first time to the best of our knowledge, we present the theory and experimental proof showing the use of cyclic pulse coding to enhance the SNR of the back-scatte...Show More

Abstract:

We propose and experimentally demonstrate the use of cyclic pulse coding for enhanced performance in distributed acoustic sensing based on a phase-sensitive optical time-...Show More
Impact Statement:
For the first time to the best of our knowledge, we present the theory and experimental proof showing the use of cyclic pulse coding to enhance the SNR of the back-scattering signal in a phase-OTDR within a single round-trip-time of light along the fiber by ~ 9dB. We present detailed source design and demonstrate a phase-OTDR sensor using direct detection and a commercial off-the-shelf DFB laser, which is more cost-effective compared to existing systems using stabilized narrow linewidth lasers.

Abstract:

We propose and experimentally demonstrate the use of cyclic pulse coding for enhanced performance in distributed acoustic sensing based on a phase-sensitive optical time-domain reflectometry (φ-OTDR) using direct detection. First, we present a theoretical analysis showing that to make cyclic pulse coding effective in φ-OTDR, the laser linewidth and stability must be optimized to simultaneously guarantee intrapulse coherence and interpulse incoherence. We then confirm that commercial off-the-shelf distributed feedback (DFB) lasers can satisfy these conditions, providing coding gain consistent with theoretical predictions. By externally modulating such lasers with cyclic pulse coding, we demonstrate a distributed acoustic sensor capable of measuring vibrations of up to 500 Hz over 5 km of standard single-mode fiber with 5-m spatial resolution with ~9-dB signal-to-noise ratio (SNR) improvement compared with the single-pulse equivalent. We also show that the proposed solution offers sensing performances that are comparable to similar sensors employing highly coherent and stabilized external cavity lasers and a single-pulse φ-OTDR.
A cost-effective distributed acoustic sensor using a commercial off-the-shelf DFB laser and direct detection phase-OTDR.
Published in: IEEE Photonics Journal ( Volume: 8, Issue: 1, February 2016)
Article Sequence Number: 6800210
Date of Publication: 17 December 2015

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