Abstract
Brillouin-based fi ber-optic sensors have been intensively studied because they can provide distributed strain/temperature sensing applicable to the large-scale monitoring of strain/temperature in optical fi ber communication lines or civil engineering structures. In this paper, we propose and demonstrate a highspeed distributed strain sensing technique based on Brillouin optical time domain analysis (BOTDA) systems using phase-modulated probe light at the modulation frequency of the same order of Brillouin bandwidth. This technique utilizes modulation format conversion from phase modulation to intensity modulation when the phase-modulated probe light experiences stimulated Brillouin scattering (SBS). Our proposed method offers high-speed distributed sensing due to frequency-sweep-free operation with simple digital processing from the probe powers sampled at fixed interval. We experimentally demonstrated the capability of high-speed distributed strain sensing.
