Digital demodulation technique for fiber-optic hydrophones based on 3 × 3 couplers

In this paper, a digitized real-time demodulation system for optical hydrophones based on a 3 × 3 coupler is proposed. The system is built as a virtual instrument via the dynamic data acquisition platform from NI company. Compared with the commonly used systems composed of analogue circuits, the proposed system has better accuracy and is more flexible in applications. The error analysis of the proposed system is also given.