Long range Brillouin optical time-domain analysis using cyclic m-sequence

For Brillouin optical time domain analysis (BOTDA), the state-of-the-art encoding schemes are usually developed based on the Golay code, the simplex matrix, and the cyclic (simplex) pulse coding. In this work, we propose a convenient BOTDA encoding scheme employing the pseudo-random binary sequence (PRBS). The pump laser is constructed based on the m-sequence with unipolar, return-to-zero (RZ) code chips. Correspondingly, a correlation function with bipolar, one-hot code chips is introduced to realize a fast demodulation. In the demonstration experiment, a 10-th order m-sequence (length is 1023) is used in the PRBS BOTDA, achieving 0.64 MHz BFS resolution and 4.4 m spatial resolution near the 50.4 km fiber far-end, within 40 s measurement time (0.4 s averaging × 100 scanning frequencies).