Effect and elimination of alignment error in an optical fiber current sensor.

This Letter demonstrates the effect and elimination of alignment error in an optical fiber current sensor. An optical model is built to illustrate the effect of alignment error, which does not induce zero drift and has a large effect on output accuracy. The total alignment error and modulation angle of the polarization controller are defined as k and θ, respectively. Parameter t is equal to 2θ-2k. An elimination method of the error k is proposed, which corrects the angle θ to keep parameter t at 90 deg. This method avoids the measurement of all splice angles separately. Its feasibility is shown by simulation results. In addition, the measurement method and conditions of parameter t are presented. The final t is about 90.24 deg. Furthermore, the effectiveness of the proposed elimination method is proven by a performance test.