Distributed fiber vibration sensing with single-shot measurement and moving time-gating method

The single-shot measurement method is proposed to improve measurement accuracy in distributed dynamic strain sensing by using time-resolved optical frequency domain reflectometry (OFDR). Time-domain information can be obtained without reference scan by single-shot measurement with standard polarization-maintaining fiber as the sensing fiber via auto-correlation calculation to measure Rayleigh backscatter spectrum in different wavelength ranges. Experimental results verify that the information of vibrated and non-vibrated state can be determined by monitoring the side peak shifts in the local Rayleigh backscatter spectrum along the sensing fiber. Furthermore, moving time-gating method is illustrated and used to broaden the detection bandwidth. The effective sampling rate can be increased so that the measurable frequency range can be further increased. In the further proof of concept experiment, for a conventional OFDR system, the measurable frequency of vibration event can be achieved up to 30Hz along the polarization-maintaining fiber with a tunable laser sweeping rate of 40nm/s by single-shot measurement and moving time-gating method. The measurable frequency range could be further broadened by using tunable laser sources with higher sweeping speeds. The proposed schemes provide new approach to enhance the measurement accuracy via single-shot measurement in the OFDR system which is of great significance in distributed dynamic signal detection system.