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22 August 2011 Method of coherent detection with a shared line based on acousto-optic deflection
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In the conventional coherent detection method, almost all the techniques of splitting and combining homologous light source have been adopted, as a result of which the coaxial adjustment of signal and reference light becomes quite complex and the energy utilization is rather low. This paper presents a new coherent detection method with a shared line based on acousto-optic deflection. By the way of analyzing the optical structure and the principle of frequency measurement, it proposes basic measures and solutions to improving the system's accuracy and resolution of instantaneous frequency measurement. Best use has been made of the characteristics of the diffracted spots so as to optimize the optical path structure and to make the effective superposition of 0 level spot and 1 level diffracted spot, thus realizing the tracking and measurement of electromagnetic spectrum signal. Experiments show that application of the acousto-optic signal processing method in coherent detection can overcome the contradiction between the frequency resolution and the instantaneous bandwidth of traditional communication receiver and meet the demands of the communication system to high intercepted probability, large instantaneous bandwidth, as well as rapid measurement of pulse. In comparison with the conventional coherent detection method, this method can make the power of light source reduce by 50%, and receiver's sensitivity much better than -65dBm, and then the intercept probability reached up to 100%. Moreover, the frequency resolution is better than 100KHz.All this can achieve the seamless measurement of carrier frequency.
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Jiang Zhou, Ning He, and Xin Liao "Method of coherent detection with a shared line based on acousto-optic deflection", Proc. SPIE 8192, International Symposium on Photoelectronic Detection and Imaging 2011: Laser Sensing and Imaging; and Biological and Medical Applications of Photonics Sensing and Imaging, 81923F (22 August 2011);

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