In this paper, realized methods of distributed optical fiber sensing technique and a kind of sensing technique based on the Sagnac optical interferometer theory were summarized. The relationship between leakage position and phase difference (phase noise and receiving power) microbend loss is analyzed and simulated. We acquire that receiving power's increment will lead to phase noise's decrement. When faced with different wavelengths, phase noise differ. For the leakage position and phase difference,when wavelength is 1550nm, its resolving power can reach 0.148rad/m.