Distributed fiber optic sensing based on counterpropagating waves

The spatially and temporally resolved birefringence of a single-mode optical fiber can be ascertained using backward stimulated Raman scattering. The magnitude of the birefringence is determined from the optical power exchanged between two counterpropagating light pulses. The degree to which a signal pulse is amplified by a pump pulse is governed by their relative states of polarization when they overlap. A novel normalization procedure is proposed that eliminates many of the unknowns. An example of how this technique could be used to evaluate a distributed strain field is provided.