Overcoming acoustic crosstalk in the BOTDA sensor with a bidirectional frequency-modulated probe.

ABSTRACT

Conventional Brillouin optical time-domain analyzer (BOTDA) with a frequency-modulated probe (FMP) could avoid non-local effects, while still suffering from the acoustic crosstalk between different frequencies. The induced Brillouin frequency shift (BFS) measurement errors over the whole sensing fiber link reduce system certainty subsequently. A BOTDA scheme with a bidirectional frequency-modulated probe (BFMP) is proposed to overcome such an effect. It utilizes BFMP to generate the crosstalk of the same magnitude and opposite direction to compensate each other. Experimental results indicate that the pulse interval of the coded sequence could be reduced to ∼500 ns to improve the measurement efficiency and BFS estimation errors (∼2.2 MHz) over 117.46-km sensor link are eliminated simultaneously.