Spontaneous Brillouin distributed optical riber temperature sensing system based on all fiber Mach-Zehnder interferometer

Based on the temperature dependence of the intensity of Brillouin scattering in optical fiber, a distributed optical fiber temperature sensing experimental system with Brillouin OTDR configuration was presented. In this system, a narrow line width LD was used as a light source. The output of LD was modulated into light pulses by an AOM. After amplified by an EDFA the light pulses were coupled into the test fiber to generate backscattering signal. A double-pass Mach-Zehnder interferometer was used to separate the spontaneous Brillouin scattering from the Rayleigh scattering. The temperature sensing experiments were carried out on two different length of fibers which were 4.25 kin and 22 km long, respectively. The intensity changes in the Brillouin scattering signals due to temperature variation on both of the fibers were measured.