Polarization dependent inter-core interferences in twin-core photonic crystal fiber and its application to high temperature measurement

We investigate polarization dependent differential group modal index sensitivity to temperature in twin-core photonic crystal fiber. Characteristics of guided modes and the group modal index difference in twin-core photonic crystal fiber (TC-PCF) are numerically analyzed. The geometrical asymmetry between the two cores induces significantly reduced power coupling between two core modes and difference in their effective indices. Two cores form two effective optical paths. We also experimentally demonstrate polarization dependent differential group modal index sensitivity to the temperature. Since the TC-PCF has polarization dependent group modal index difference, TC-PCF based interferometer shows input polarization dependent free spectral range and temperature sensitivities. The effective index difference between the two core modes tends to increase when the temperature increases.