Faraday Mirror-typed Optical Current Transformers And Its Theoretical Analysis

Utilizing a Faraday rotation mirror, a Faraday rotation mirror-typed optical current transformer (OCT) design with turn-back optical paths is proposed to overcome the harmful effects of reciprocal optical parameters such as the linear birefringence and reflection-induced retardation inside the bulk glass current sensing head, and to multiply the sensing signal. The theoretical analysis of the working principle, the simulation results of the polarization state of the output light and the comparison between it and that of the OCT with polarization-preserving total reflection (PPTR) layers are presented. The results show that this design has a good restraining effect on the degeneration of the polarization state of the output light. Besides, the effects of some kernel devices such as Faraday mirror and non-polarization beam spliter (NPBS) are also analyzed theoretically. The results show that the practical rotation angle of the Faraday mirror can induce a system error to the output and the reflection-induced retardance of the NPBS may degenerate the state of polarization of the output light beam. These results might have certain reference significance on the performance improvement of the present bulk glass OCT, and the development of practical OCT.