Polarimetric optical fiber sensor using a frequency stabilized semiconductor laser

Improved performance of a polarimetric optical fiber sensor for remote temperature measurement by the use of a frequency-stabilized semiconductor laser is discussed. The temperature change is measured from the phase delay between two orthogonally polarized modes in a polarization-maintaining fiber. The sensor output signal is demodulated utilizing direct modulation of the laser frequency. The center frequency of the modulated laser is locked to a Fabry-Perot interferometer by controlling the injection current. The minimum detectable temperature is evaluated experimentally to be less than 0.005 degrees C, which is several times smaller than that obtained with the free-running laser.<>