Fiber-optic current sensor using an internal trigger sampling technique

We present an advanced demodulation technique for a fiber-optics interferometric current transducer. A quadrature sampling method with internal triggers was adopted for structural simplification and cost-effective phase demodulation. The internal triggers for quadrature signal processing were generated at zero crossing points of an ac-coupled reference signal, which was distinguished from the current-induced interference signal by utilizing fiber Bragg grating. Phase variation was extracted from the arctangent demodulation process. The proposed technique demonstrated accurate and stable phase demodulations performance and better than that of the conventional lock-in amp demodulation.