A Distributed Brillouin Temperature Sensor Using a Single-Photon Detector

We propose a distributed Brillouin temperature fiber sensor using a single-photon detector. In our scheme, the Rayleigh/anti-stokes ratio is used to measure the temperature information along the sensing fiber. A cascading fiber Bragg grating filter is employed to separate Brillouin anti-stokes signals from the backscattering Rayleigh light with a
$\sim 23$
dB high rejection ratio. Benefiting from the high sensitivity of the single-photon detector, the system exhibits a dynamic range of 18 dB (corresponding to 90-km sensing length) with a measured temperature error of 1 °C without any optical amplification. Furthermore, the sensor shows a 1.2 m spatial resolution and 1.7 °C temperature error with an 8.5 dB dynamic range, which means the sensing length can be extended to 42.5 km. This scheme can simultaneously achieve a large dynamic range and a high spatial resolution.