Effect of laser linewidth on phase-OTDR based distributed vibration sensing regime

Abstract

The effect of fiber laser linewidth on the optical time-domain reflectometer based vibration distributed sensing regime is studied experimentally in this paper. Lasers with multi-longitudinal modes, 5 kHz and ~800 Hz linewidth single longitudinal mode are interrogated as light source successively. Experiments show that narrower linewidth laser results in higher repeatable and stable scattering spectrum. When the 800 Hz linewidth laser is modulated into 50 ns width pulses, the signal to noise ratio is ~ 6 dB and the spatial resolution is improved to 3 m, breaking the traditional theory limit.