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.