BRILLOUIN OPTICAL-FIBER TIME-DOMAIN REFLECTOMETRY

We report on Brillouin optical-fiber time domain reflectometry (BOTDR) for distributed temperature or strain measurement along a single-mode optical fiber. BOTDR uses Brillouin scattering in optical fibers, who se Brillouin frequency shift increases in proportion to temperature or strain induced in the fiber. This method requires access to only one end of a fiber, as with conventional optical time domain reflectometry (OTDR) which uses Rayleigh scattering in optical fibers. In BOTDR, a coherent optical detection method is used as a backscattered light det ection technique. This technique can achieve both high sensitivity and high frequency resolution and easily separate a weak Brillouin line f rom a strong Rayleigh scattering peak and Fresnel reflected light. Exp erimental results show the potential for measuring temperature and str ain distribution with respective accuracies of +/- 3-degrees-C or +/- 0.006%, and a spatial resolution of 100 m in an 11.57 km long fiber.