Effect of pulsewidth on strain measurement accuracy in Brillouin-scattering-based fiber optic sensors

Fabien Ravet; Xiaoyi Bao; Liang Chen

doi:10.1117/12.567240

16 November 2004 Effect of pulsewidth on strain measurement accuracy in Brillouin-scattering-based fiber optic sensors

Fabien Ravet, Xiaoyi Bao, Liang Chen

Proceedings Volume 5579, Photonics North 2004: Photonic Applications in Telecommunications, Sensors, Software, and Lasers; (2004) https://doi.org/10.1117/12.567240
Event: Photonics North, 2004, Ottawa, Ontario, Canada

Abstract

Distributed Sensors based on Brillouin scattering are attractive candidates to monitor structural health of mechanical structures. Currently physical limitations of time resolved techniques do not allow extracting accurate strain when pulsewidth is larger than strained length. The purpose of this study was to quantify the errors in such a case and derive a decision threshold making possible the discrimination of strained section from unstrained contribution. We achieved these goals by solving the coupled intensity equations for various strained lengths, pulsewidths, strain strengths, Brillouin linewidths, Fibre lengths, probe and pump powers. We observed two dominating behaviours principally functions of strained length and strain strength. In the first regime, a single peak broader than Brillouin natural gain/loss peak was detected. In the second case, we could distinguish two peaks. From these behaviours we then derived curves relating Brillouin peak contrast as well strain accuracy to the ratio between strained section length and pulsewidth. These curves also show a strong dependence on strain amplitude. This led us to find a strain induced frequency shift threshold characterising the transition from the single peak regime to the double peak regime. Finally we defined a Rayleigh equivalent criterion that unambiguously separates strained from unstrained contributions.

Citation Download Citation

Fabien Ravet, Xiaoyi Bao, and Liang Chen "Effect of pulsewidth on strain measurement accuracy in Brillouin-scattering-based fiber optic sensors", Proc. SPIE 5579, Photonics North 2004: Photonic Applications in Telecommunications, Sensors, Software, and Lasers, (16 November 2004); https://doi.org/10.1117/12.567240

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