Re-Entry Fiber Optic Current Sensor Based on Continuous Light Source

This paper proposes a re-entrant optical fiber current sensor based on continuous light, which achieves continuous measurement while improving current measurement sensitivity. Based on the traditional re-entry structure, the sensor employs continuous light measurement, where the current signal manifests as a phase difference between two circularly polarized lights caused by the Faraday effect. This phase difference results in an interference pattern reflected in the light intensity changes. The final measured signal is the cumulative interference signal light intensity of different cycles, demodulated using the phase-generated carrier technology. Experimental results demonstrate that the sensitivity of the structure is 1.8 times that of the traditional reflective structure under the same configuration, and the current measurement accuracy is 0.8 mA. The sensitivity can be further improved by reducing the losses within the resonant cavity. This scheme offers a new approach for the low-cost application of re-entrant structures in the field of current measurement.