Polarimetric heterodyning fiber grating laser sensors

Fiber grating laser sensors have been attracting interest because of their high signal-to-noise ratio and narrow linewidth that permit high resolution sensing. According to the working principle, fiber grating laser sensors can be classified into two types: wavelength encoding sensor and polarimetric heterodyning sensor. The former converts measurrand into shift in the operation wavelength of the fiber laser, which is similar to that of fiber grating sensor. The latter converts measurrant into change in beat frequency between the two orthogonal polarization modes from the laser. Because the beat frequency is in radio frequency (RF) range, the polarimetric heterodyning sensor has distinctive advantages of ease of interrogation and avoidance of expensive wavelength measurement that is required for wavelength encoding sensors. In this paper, we report some of our recent works in fabrication of dual-polarization fiber grating lasers, development of polarimetric heterodyning fiber grating laser sensors for measurement of acoustic wave, acceleration, lateral force, displacement, electric current and hydrostatic pressure, and sensor multiplexing in RF domain.