Range Elongation of Distributed Discrimination of Strain and Temperature in Brillouin Optical Correlation-Domain Analysis Based on Dual Frequency Modulations

A scheme of dual frequency modulations are proposed for one-laser Brillouin optical correlation-domain distributed discrimination of strain and temperature. A lower frequency modulation is additionally applied to the laser source, which is originally modulated by a higher one for distributed generation and detection of Brillouin dynamic grating. This scheme can suppress the unwanted correlation peaks due to the higher frequency modulation so as to elongate the measurement range with keeping the high spatial resolution. In this experiment, the measurement range is increased from ~ 5 to 34 m with the spatial resolution maintained to be 10 cm.