Performance improvement for long‐range BOTDR sensing system based on high extinction ratio modulator

The leakage light of an electro‐optic modulator induced by its finite extinction ratio (ER) may degrade the performance of the Brillouin optical time domain reflectometer (BOTDR) sensing system, especially for long distance measurement. A novel configuration of a modulator based on a synchronous optical switch is presented. Experimental results have shown that the performance of the sensing system can be obviously improved with the proposed high ER modulator. At the end of a 48.5 km sensing fibre, the maximum uncertainty of temperature measurement has been reduced from 5.2 to 0.8°C with a 25 m spatial resolution after making an improvement in the ER from 35 to 65 dB.