Distributed optical fiber sensing of BOTDA based on double sideband

A distributed fiber sensing method of dual-sideband pump BOTDA is proposed, which achieves the improvement of strain accuracy. The BOTDA scheme with dual-sideband pump pulses is designed, and the Brillouin gain spectrum and Brillouin loss spectrum are reconstructed by scanning frequency. The additive noise is eliminated by the process of multiple averaging. The synthetic spectrum is constructed by combining Brillouin gain spectrum and Brillouin loss spectrum to eliminate the multiplicative noise. The proposed synthetic spectrum effectively improved the signal to noise ratio of the system. The strain can be demodulated by using Lorentz fitting and Brillouin frequency shift extraction of the constructed synthetic spectrum. Experimental results show that the standard deviation of strain with the 2 m spatial resolution demodulated by this method is only 0.1611 MHz (3.406 με), which is 34% higher than that of the single Brillouin gain spectrum. The proposed method improves the signal to noise ratio of the system, so as to achieve high-accuracy demodulation of the strain.