A chiral photonic crystal fiber sensing coil for decreasing the polarization error in a fiber optic current sensor

The residual linear birefringence inside the sensing coil is one of the main factors causing polarization error and accuracy decline of a fiber optic current sensor. To relieve the residual linear birefringence in fiber optic current sensors, a chiral photonic crystal fiber was utilized as the sensing coil, whose air filling ratio, lattice constant and chiral parameter were designed according to the analysis of the circular polarization degree affected by the diameter variation of the innermost air holes. The simulations demonstrated that there is a better circular-polarization-maintaining performance for the chiral photonic crystal fiber than that for the screwed silicon-based fiber. As the sensing coils, it is by an order of magnitude that the accuracy of current measurement is improved in the fiber optic current sensor.