IEEE ICHVE 2022 / 1-PAGE ABSTRACT
Design of high-precision optical interferometer phase demodulation system
Yuan WANG, Zhanglin CHEN, Yangyang XIE, Hao LIU, Weiqi QIN, Guoming MA
State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources, North China Electric Power University, Beijing, China
ncepu_ywang@163.com

Purpose/Aim
When power equipment fails, ultrasonic and thermal signals are often generated. The phase of the optical signal in the optical interferometer changes due to the fault signals. In the previous research, the differential-cross multiplication (DCM) algorithm is used to demodulate the phase of the beat signal of the optical interferometer, and this process is normally realized by software. However, the current software-based phase demodulation algorithm has problems such as a large amount of data, and a long calculation time. DCM algorithm is difficult to meet the needs of online monitoring.
Experimental/Modeling methods
In this paper, a new phase demodulation scheme based on AD8302 chip is proposed. Through dual AD8302, the influence of nonlinear region in the output characteristic curve is effectively solved. The circuit design and the selection of key components are completed, the integrated PCB circuit board is designed and processed. In this paper, the optical phase is periodically modulated by a PZT, and the demodulation performance is verified by the proposed demodulation system.
Results/discussion
The results shows that the output voltage has a good linear relationship with the input phase signal, and there is no nonlinear effect. In addition, the minimum detectable phase amplitude of the developed demodulation system is about 0.85 mrad, the amount of stored data is only tens of kB, and a single demodulation takes only a few seconds.
Conclusions
This work provided a new phase demodulation system for optical interferometer. The developed demodulation system can quickly and accurately find the fault of the power equipment, which brought new possibility for on-site monitoring.

optical interferometer,phase demodulations,AD8302,online monitoring