Dual-channel fiber optic current sensor based on carrier-transposed demodulation technique

A dual-channel fiber optic current sensor based on carrier-transposed demodulation technique is proposed and experimentally demonstrated. The system is implemented by adding another sensing channel to a standard reflective fiber optic current sensor, which shares numerous key optical devices without much additional expense. The output properties of the system are theoretically analyzed and numerically investigated to demon-strate the feasibility of independent current measurement at different operating frequencies. And the current sensitivity can be flexibly adjusted by changing the modulation amplitude. Based on the carrier-transposed demodulation technique, the current sensing information of both channels can be obtained independently and the cross-talk between them can be eliminated tactfully. The experimental results demonstrate that the current measurements for both channels are well independent and the channel-to-channel influences is relatively low with the standard deviation of 0.0197 mV and 0.0141 mV, respectively. The proposed scheme provides a promising approach for dual-channel current measurement with the advantages of compactness and simplicity and can be applied in practical applications without much additional cost.