为了将声光移频器(AOFS)应用至光锁相环路中实现锁相环路快速精密调谐, 并保证相干接收机接收信号的质量, 介绍了AOFS的移频原理以及在锁相环路中的动态工作模式, 对AOFS的插入损耗特性进行了系统的研究, 着重分析了AOFS驱动器功率变化以及移频过程中频率变化对插入损耗的影响。设计并搭建了基于光拍频方法的1550 nm AOFS插入损耗测量实验系统, 测试得出AOFS在各种外界调制信号影响下插入损耗的变化规律, 分析了多种影响因素共同作用下插入损耗的整体动态变化趋势并进行实验验证。根据实验分析结果对AOFS驱动功率进行优化, 结果表明, 将驱动器功率设置为1 W, 相比于25 mW驱动功率, AOFS插入损耗值在移频范围内整体下降15 dB, 最大相对插入损耗值下降1 dB。

In order to apply the acousto-optic frequency shifter (AOFS) to the optical phase-locked loop for the fast and accurate tuning and to ensure the quality of the signal received by coherent receiver, we introduce the frequency shift principle and the dynamic operation mode of the AOFS in the phase-locked loop, study the insertion loss characteristics of the AOFS systematically, and analyze the effects of power variation of driver and frequency variation in frequency shift process on insertion loss. We design and build a test system for the insertion loss measurement of 1550 nm AOFS based on the beat frequency method. The test results show the variation in the insertion loss under the influence of various modulation signals, and the global dynamic variation trend of insertion loss under multiple influencing factors is also analyzed and verified experimentally. The driving power is optimized according to the experimental results of the AOFS. The optimization results show that the AOFS insertion loss declines by 15 dB in the range of frequency shift when the driving power increases from 25 mW to 1 W, and the maximum relative insertion loss declines by 1 dB.