Influence of non-perfect extinction ratio of electro-optic modulator on signal-to-noise ratio of BOTDR

The effect of leakage light of an electro-optic modulator (EOM) on the performance on a Brillouin optical time domain reflectometer (BOTDR) is investigated theoretically and demonstrated experimentally. It is proved that in a frequency-scanning BOTDR, the leakage light gives rise to additional noise term, and deteriorate the measurement accuracy of Brillouin frequency shift (BFS) and temperature. The maximum temperature measurement uncertainty of the 23.9 km fiber increases from 1.9 °C to 5.6 °C when the ER of EOM decreases from 50 dB to 25 dB.