A fiber-optic CT using a reflection type Sagnac coil and a time- delayed sampling demodulation

摘要

We propose a fiber-optic interferometric CT that uses a time-delayed sampling signal processing to extract the current-induced phase information. The interference signal of the reflection type Sagnac sensor coil is sampled with a carefully adjusted time delay. And the phase is extracted by using an arctangent demodulation. The accuracy comparison between the proposed and a lock-in amplifier demodulation showed the feasibility of the proposed technique. Also the outputs from a flint glass sensor coil and a standard fiber sensor coil were compared in the same condition, proving the low birefringence of the flint glass shows the better performance. The phase measurement accuracy of the proposed demodulation technique was about 8.09 mrad.