Polarimetric heterodyning Bragg-grating fiber-laser sensor.

We report the operation of an active, single-frequency, polarimetric, Bragg-grating fiber-laser strain sensor. The short Bragg-grating fiber-laser design limited lasing to two orthogonal polarization modes that, when optically mixed, yielded a single beat frequency that varied at a rate of -4.1 MHz/mstrain for linear strain and -0.37 MHz/(deg/cm) for torsional strain.