A calibrated 27-km distributed fiber temperature sensor based on microwave heterodyne detection of spontaneous Brillouin backscattered power

Single-ended distributed fiber temperature measurements using the novel technique of microwave (11 GHz) coherent detection of spontaneous Brillouin backscattered power are presented. Anti-Stokes power traces mere obtained for a sensing length of 27.4 km, believed to be the longest yet demonstrated for such spontaneous power measurements. The power dependence on temperature was measured as 0.36/spl plusmn/0.04%/K, and the rms temperature error was less than 3.5 K at the far end of the sensing fiber.