EOM bias control scheme in BOTDR system

In Brillouin optical-fiber time-domain reflectometry (BOTDR) system, it is important to keep the pulse energy uniform for a constant extinction ratio, so an electro-optic modulator (EOM) is used to turn the probe beam on and off to produce the pulsed probe beam. However EOM´s job characteristics slowly changes due to many factors, which led to the instability of the pulse energy after modulation. Therefore drift compensation is absolutely necessary. In this paper, the use of low-frequency sinusoidal signal as the disturbance signal to judge the drift direction of the EOM performed admirably, and highly improved the extinction ratio, which increased from 7.36 dB to about 25 dB. So with this bias voltage control system, a higher sensing accuracy can be getting in the BOTDR system.