Enhancing the measurement range of a Brillouin based fiber-optic distributed temperature sensor by improving receiver sensitivity through optical preamplification

We report on the use of a cost-effective erbium-doped based optical preamplifier in a single-ended distributed fiber-optic sensor to improve receiver sensitivity and hence measurement range. The improved accuracy of spontaneous Brillouin measurements was demonstrated in a 23 km sensor and was limited by amplified spontaneous emission from the preamplifier, which was verified theoretically. Reduction of amplified spontaneous emission was achieved with a 0.37 nm in-fiber Bragg grating. A signal-to-noise improvement of 17 dB was achieved and supported by theory, which translates to approximately 40 km range improvement for a single-mode sensing fiber having losses of 0.2 dB/km at 1550 nm.