Phase method of measuring a signal in fiber-optic birefringence-type sensors

A phase method of measuring the phase retardation that occurs in the fiber-optic birefringence-type sensor and that is caused by the signal to be detected has been studied both theoretically and experimentally. The method is based on a nonmechanical low-frequency rotation of the light polarization plane at the input to the primary transducer of the sensor, which is provided by three incoherent light sources with their intensities modulated by periodic oscillations that are phase shifted by 2pi/3 rad with respect to one another. The phase-retardation measurement accuracy determined on an experimental basis was no worse than 0.1% full scale over a 2pi-rad range.