Abstract A novel scheme based on the cascade structure of a dual-polarization Mach–Zehnder modulator (DPol-MZM) and a phase modulator (PM) is proposed which can simultaneously identify the value and direction of Doppler frequency shift (DFS). A low frequency reference signal and an echo signal are modulated by the DPol-MZM into orthogonal polarization states. The transmitted signal is modulated onto the reference signal by the PM and then one side band of the modulated signal is suppressed after a filter. The value of DFS is obtained by mixing the echo signal and the transmitted signal and the direction is distinguished by mixing the echo signal and the modulated reference signal. The system has only one channel and DFS measurement only needs a low frequency electrical spectrum analyzer (ESA). The measurement error is less than 0.1 Hz. Because of the cascade modulation structure and the direct frequency mixing of the transmitted signal and the echo signal, the operation frequency range of the system is not limited by the carrier frequency and the scheme has high measurement accuracy.

中文翻译：

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基于级联调制的无模糊光子多普勒频移测量

摘要 提出了一种基于双极化马赫-曾德调制器（DPol-MZM）和相位调制器（PM）级联结构的新方案，可以同时识别多普勒频移（DFS）的值和方向。低频参考信号和回波信号由 DPol-MZM 调制成正交极化状态。传输信号由 PM 调制到参考信号上，然后调制信号的一个边带经过滤波器抑制。DFS 的值是通过混合回波信号和发射信号获得的，并且通过混合回波信号和调制参考信号来区分方向。该系统只有一个通道，DFS 测量只需要一台低频电频谱分析仪 (ESA)。测量误差小于 0.1 Hz。