Measurement of the Temperature Sensitivity of Modal Birefringence of Polarization Maintaining Fibers Using a Sagnac Interferometer

This paper presents a significantly improved method for measuring the temperature sensitivity of phase modal birefringence of polarization-maintaining optical fibers (PMFs) based on the Sagnac interferometer. In this method, a measurement of the spectral temperature sensitivity of a PMF-based Sagnac interferometer temperature sensor is performed. The measured spectral temperature sensitivity of the sensor is used to determine the polarimetric temperature sensitivity of the PMF, and with the additionally measured phase modal birefringence, to determine its temperature sensitivity of phase modal birefringence based on the derived equations relating these quantities to the spectral temperature sensitivity of the sensor. The temperature sensitivity of group modal birefringence of the fiber was calculated on the basis of its already determined temperature sensitivity of phase modal birefringence. In addition, a new procedure for determining the sign of the group modal birefringence was given, and new procedures for determining the signs of the temperature sensitivities of phase modal birefrigence and group modal birefringence of a PMF were also given. Using the proposed method, the measurements of PMFs were performed: a polarization maintaining photonic crystal fiber (PM-PCF) and a PANDA PMF, in the temperature range 20 °C-70 °C, for the wavelength range 1500-1600 nm. A comparison of the results of these measurements with results obtained by other methods for the same types of fibers is presented.