Numerical Investigation of Golay Coding Brillouin Optical Time-Domain Analysis System Based on π-Phase Pulse

A novel configuration of Golay coding based on $\pi $ -phase pulse is proposed to overcome the trade-off between the spatial resolution and the sensing range of the conventional Brillouin optical time-domain analysis (BOTDA) system. The mathematical model of hybrid coding is established by solving the three-wave coupled equations. The tests are performed to analyze the autocorrelation properties of hybrid coding and the influence of the pulse width on the Brillouin gain spectrum. Using 512-bit Golay codes combining with 500 ps phase shift pulse, signal-to-noise ratio (SNR) is enhanced by 10.53 dB to ensure that SNR at the end of the 50-km-long fiber is above 16 dB. Under this condition, the spatial resolution of 5 cm is achieved along 50 km sensing fiber.