采用光强度调制鉴相方案,使用直接数字频率合成器(DDS)和激光驱动器产生频率稳定的调制激光,注入待测光路,在待测光路后进行光电转换和放大,引入参考本振信号作为混频器相位参考信号,利用混频器测量待测光路信号与参考本振信号的相位差,获得光路延时信息。主要特点如下:提出了在本振信号链路三段移相的差分式检测方法,优化了鉴相点,提高了测量精度;采用单段短时两相位点测量模式,有效降低了光源功率波动、光路中光强波动、光电探测及放大电路增益波动、温度变化导致相位差漂移等带来的测量误差;在每个相位点多次测量采样,根据测量的平均值计算相位差,推导时间差。详细分析了测量电压和被测时延之间的函数关系,分析了影响测量精度的因素,构建验证系统,完成了实验验证。实验结果表明:本方案在4 ns的时延内的测量精度可达1 ps,大幅提升了现有高功率激光装置的同步测量精度。

In this study, an amplitude-modulation phase discrimination scheme was used. A direct digital frequency synthesizer and laser driver were used to generate a frequency-modulated laser with stable frequency. The laser was injected into the optical path to be measured, and then performed photoelectric conversion and amplification after the optical path. With regard to the phase reference signal of the frequency converter, a mixer was used to measure the phase difference between the optical path signal to be measured and the reference local oscillator signal, thereby obtaining the optical path delay information. The main contributions of this study are as follows. First, a differential detection method was proposed for the three-stage phase shift in the local oscillator signal link to optimize the phase detection point and improve the measurement accuracy. Second, a short-term two-phase point measurement mode is used in a single section to effectively reduce the measurement errors caused by the fluctuations in the light source power, light intensity in the optical path, photoelectric detection and amplification circuit gain, and phase difference drift caused by changes in temperature. Third, measurement and sampling were performed multiple times at each phase point; the phase difference was calculate based on the measured average, and the time difference was derived. The functional relationship between the measured voltage and the measured delay and the factors that affect measurement accuracy were analyzed in detail. A verification system was built, and the experimental verification was completed. The experimental results show that the scheme can obtain accuracy of 1 ps within 4-ns time delays, which can greatly improve the synchronous measurement accuracy of the existing high-power laser devices.