A BOTDA with break interrogation function over 72 km sensing length

A BOTDA with the capacity of break interrogation is proposed and demonstrated experimentally. In our configuration, coherent detection and double sideband probe method are employed to enhance the signal-to-noise ratio (SNR) and to effectively reduce nonlocal effects, respectively. Without amplification, a 72 km sensing range with 5-meter resolution and an estimated temperature uncertainty of 1.8 °C are obtained. Benefiting from the flexible optical configuration, this sensor system has the capacity of break interrogation as a coherent optical time domain reflectometry (COTDR) if there is a break in the fiber under test (FUT). The sensor achieves a dynamic range of 36 dB with a 100 m spatial resolution, which offers an excellent solution for the requisite of two-end-access in BOTDA, and significantly enhances the robustness of the sensing system.