Accurate measurements of circular and residual linear birefringences of spun fibers using binary polarization rotators.

We present a method to accurately measure the birefringence properties of spun fibers using binary polarization rotators. By taking the advantages of binary polarization rotator in polarization analysis, we are able to simultaneously measure both the circular and linear birefringences in a spun fiber with high accuracy. We obtain the circular and the residual linear birefringences of the spun fiber as a function of temperature T to be 3.34 × 10-5-5.11 × 10-8T and 8.1 × 10-6-1.19 × 10-8T, respectively, with the residual linear birefringence about 4 times less than the circular birefringence. We find, for the first time with the best of authors' knowledge, that the circular and the residual linear birefringences in a spun fiber are highly linear with the temperature, with thermal coefficients of -5.11 × 10-8 °C-1 and -1.19 × 10-8°C-1, respectively, and that the relative changes per °C of the circular and residual linear birefringence are almost identical, with values of -0.152% and -0.147% respectively. We believe that the method and data presented in this paper will be beneficial for making high quality spun fibers, as well as high accuracy fiber optic current sensors.