Novel strain- and temperature-sensing mechanism based on dynamic grating in polarization-maintaining erbium-doped...

The first experimental observation of a dynamic grating in polarization-maintaining erbium-doped fiber (PM-EDF) is reported and a novel fiber-optic strain- and temperature-sensing mechanism based on the dynamic grating in PM-EDF is demonstrated experimentally. The dynamic grating is written with light beams in one primary polarization axis of the PM-EDF, and read with a light beam in the other primary polarization axis. The readout Bragg reflection wavelength of the grating differs from the writing wavelength and the wavelength difference is proportional to the birefringence between the two polarization axes. Making use of the dependence of the birefringence on strain or temperature, strain- and temperature-sensing is realized by measuring the Bragg reflection wavelength (frequency) shift. In order to detect the weak reflection from the dynamic grating, a dual-stage synchronous detection scheme is adopted in the experiment. The results show a strain-sensitivity of 1.4 MHz/microepsilon and a temperature-sensitivity of 60 MHz/ C, respectively.