Research on the Application of Acousto-optic Signal Processing in Coherent Detection

In the intensive, complex and variable electromagnetic signal environment, traditional electronic receiver cannot fully meet people's requirements. To overcome the "bottleneck" that appears in electronic receiving system and improve the detection and interception capabilities of receiving system, the scheme that the acousto-optic signal processing is introduced to coherent optical detection system is proposed. On the basis of traditional coherent receiving technology, the effect of ups and downs of random noise is reduced by the use of acousto-optic device. And it improves selectivity of signals and enhances the capacity of suppressing noise. Thus signals of smooth amplitude and the higher signal to noise ratio (SNR) are provided for the back-end signal processing. Based on frequency measurement principle of acousto-optic deflector, diffraction efficiency of incident light is researched, when signals of different frequencies are as the driver of acousto-optic deflector. By the analysis of the forming principle of ultrasonic grating and the phase mismatching factor, in theory spatial filtering of acousto-optic deflector is got, which suppresses the impacts of unwanted signals on signal detection, meets the requirements of instantaneous frequency measurement and enhances separation ability of signals arriving simultaneously. At the same time, coherent optical detection system based on acousto-optic effect is constructed and experimental tests are carried out. The experimental result is consistent with theoretical analysis. And it is conductive to detect and process weak signal.