Optical fiber distributed vibration sensing system using time-varying gain amplification method

A time-varying gain amplification method is proposed and demonstrated in an optical fiber distributed vibration sensing system based on a phase-sensitive optical time-domain reflectometer. An acoustic optical modulator is adopted to generate narrow pulses, which are injected to the sensing fiber to generate Rayleigh backscattering light. The experimental results show that a 5-m spatial resolution and up to 44-km sensing range with 50-ns pulse width are achieved. The amplitude of vibrations is equal in three positions including 804, 20,054, and 43,455 m.