In this paper

we propose a novel sensor structure that can improve the signal-to-noise ratio of Brillouin Optical Time Domain Reflectometer（BOTDR） by using a nonlinear reflector

which is constructed by a 3 dB coupler with two sensing fibers of the same type placed in the same temperature or strain circumstance.Due to the constructive inference of the nonlinear reflector

the output signal intensity of the sensing system is raised four times that when only one sensing fiber is used

improving both the system SNR and measurement accuracy but also the system reliability.