Polarimetric sensitivity of a three-mode elliptical-core fiber to strain

We measured polarimetric sensitivity of a three-mode elliptical-core fiber to strain for all spatial modes. Phase and group modal birefringence were also determined for all modes to fully characterize the investigated fiber. Experimental results show a very high difference in fiber sensitivity to strain versus mode order. It changes the sign from negative for E-11 mode to positive for E-31 mode. This effect can be potentially employed in polarimetric strain sensors. We also modeled all measured parameters using Optiwave BPM-Cad and Cosmos/M software packages. The measured values of phase and group modal birefringence agree well with those obtained from calculations for all spatial modes. Unfortunately, we observed poor agreement between experimental and calculated values of strain sensitivity, which is most probably caused by the lack of reliable material constants for SiO2/GeO2 glasses.