150-km-range distributed temperature sensor based on coherent detection of spontaneous Brillouin backscatter and in-line Raman amplification

Abstract

We report an extended-range distributed temperature sensor based on coherent detection of the frequency shift of the spontaneous Brillouin backscatter combined with Raman amplification. We achieved the Raman amplification within the sensing fiber using either a copropagating or counterpropagating Raman pump with respect to the probe pulse, and experiments were conducted to investigate the optimum pump and probe power combination. With a copropagating Raman pump a temperature resolution of 0.8°C was achieved at a sensing range of 100 km, and with a counterpropagating Raman pump a temperature resolution of 5.2°C was achieved at a sensing range of 150 km with 50-m spatial resolution.