Polarization Diversity Scheme for BOTDA Sensors Based on a Double Orthogonal Pump Interaction

We introduce a Brillouin optical time-domain analysis (BOTDA) sensor deploying a novel polarization diversity technique based on the use of two orthogonal pump pulses, which simultaneously interact with a phase-modulated probe wave. The orthogonality of the two pump pulses guarantees that two complementary Brillouin interactions take place at each position of the fiber so that polarization independent measurements are performed throughout the fiber even if no averaging is applied. This feature can be exploited in dynamic distributed BOTDA sensors to reduce the measurement time, as no extra averaging is required to compensate the polarization dependence of Brillouin interaction. Proof-of-concept experiments demonstrate the feasibility of the technique by employing a completely passive scheme to generate the orthogonal pump pulses. Furthermore, the technique is stable and easy to implement, making it a perfect candidate for practical sensor implementations.