Long-range distributed temperature and strain optical fibre sensor based on the coherent detection of spontaneous Brillouin scattering with in-line Raman amplification

Al Ahbabi, Mohammed Nasser, Cho, Yuh Tat and Newson, Trevor P. (2006) Long-range distributed temperature and strain optical fibre sensor based on the coherent detection of spontaneous Brillouin scattering with in-line Raman amplification. Measurement Science and Technology, 17 (5), 1082-1090. (doi:10.1088/0957-0233/17/5/S24).

Abstract

We report an extended range distributed temperature and strain optical fibre sensor based on the coherent detection of spontaneous Brillouin scattering combined with Raman amplification. The Raman amplification was achieved within the sensing fibre using either co- or counter-propagating Raman pump configuration with respect to the probe pulse and experiments were conducted to investigate the optimum pump and probe power combination. Using Brillouin frequency shift measurements with co-propagating Raman pump configuration, a temperature resolution of 1.7°C with a 20m spatial resolution at 100km was achieved. With the counter-propagating pump configuration, a temperature resolution of 5°C with a 50m spatial resolution at 150km was achieved. Measuring both the power and frequency of the Brillouin signal, a simultaneous temperature and strain measurement was performed over 50km using co-propagating Raman pump. Temperature and strain resolutions of 3.5°C and 85 mu.epsilon with 5m spatial resolution were achieved.

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