Sagnac loop interferometer based on polarization maintaining photonic crystal fiber with reduced temperature sensitivity.

A Sagnac loop interferometer based on polarization-maintaining photonic crystal fiber was built and analyzed. Mainly the temperature dependence of the Sagnac loop filter function was measured and analyzed. By measuring the filtering function of the Sagnac loop as a function of the temperature over 200 degrees C, we deduced an unambiguous temperature dependent birefringence coefficient, d n/dT = 2.0 x 10-9 /K. Over the full temperature swing, the maximum peak shifts was less than 10% of the filter period. For comparison, a standard Sagnac loop was built with the exact same length and experimental condition, where we deduced d n/dT = 7.0 x 10-8 /K.