A self-heterodyne detection Rayleigh Brillouin optical time domain analysis system

To enhance the signal intensity and eliminate the effect of laser frequency instability in Rayleigh Brillouin optical time domain analysis system, a self-heterodyne detection technique is proposed to improve the performance of the system. The principle of self-heterodyne detection to enhance the signal intensity and eliminate the effect of laser frequency instability is introduced on the basis of the analysis of Rayleigh Brillouin optical time domain analysis system, and a wavelength scanning based signal averaging method to reduce the coherent fading noise and improve the signal-to-noise ratio is discussed. The experimental results using an experimental setup based on the proposed techniques show that on a 50-m-long fiber near the fiber end, the amplitude fluctuation and the signal-to-noise ratio with 17 wavelength scans are 0.852 dB reduced and 4.0 dB enhanced compared to those with single wavelength, the Brillouin frequency shifts on the 50-m-long fibers of the heated section and near the fiber end can be accurately measured by maximum fluctuations of 0.84 MHz and 1.09 MHz that are equivalent to temperature measurement accuracies of 0.84 °C and 1.09 °C, which indicates that the proposed techniques can realize high-accuracy measurement and have huge potential in the field of long-distance and high-accuracy sensing.