Distributed optical fiber Raman temperature system with an optical fiber ring

For restraining the temperature excursion accumulation and the anti-Stokes back-scattering intermingling with the Rayleigh back-scattering, an optical fiber sampling ring was set after an inswept death section of the sensing optical fiber. The anti-Stokes back-scattering was demodulated by Rayleigh back-scattering and the fiber's temperature was calculated by the sampling ring, which advanced the temperature precision and stability of the system. A 10 ns, 100 mW, 1.55 μm pulse laser, a 15 dB gain of EDFA, two high sensitive and low noise APD, two100M14bitA/D and two DSP chips using for 212~213 digital average form the experimental system. The spatial resolution of 1 m and temperature resolution of 0.03 ℃ were achieved using these techniques.