We propose and demonstrate a photonic delay line based carrier suppression interferometer system for measuring the phase noise of microwave sources. We show both theoretically and experimentally for the first time that carrier suppression is capable of suppressing the effects of the residual phase noise of the microwave amplifiers and the relative intensity noise of light in the system by up to 70 dB, and therefore effectively eliminates the contributions of these noise sources to the noise floor of the phase noise measurement system. Using a 2-km photonic delay line, we achieved phase noise measurement floors of −126 dBc/Hz at 1 kHz and −152 dBc/Hz at 10 kHz around a 10 GHz carrier, respectively, which are 15 and 20 dB lower than those of a frequency discriminator based phase noise measurement system using the same length of fiber delay and the same optical and microwave components. The noise floor of −152 dBc/Hz at 10 kHz is also 8 dB and 17 dB lower than those of a Keysight E5052B phase noise measurement system with 100-times cross-correlation and without cross-correlation, respectively. Even lower phase noise floors are expected for such a carrier suppression system if microwave phase shifters with lower residual phase noise or a longer photonics delay line are used.

中文翻译：

---

使用光子延迟线实现的载波抑制对微波源进行超低相位噪声测量


我们提出并演示了一种基于光子延迟线的载波抑制干涉仪系统，用于测量微波源的相位噪声。我们首次从理论上和实验上证明，载波抑制能够将微波放大器的残余相位噪声和系统中光的相对强度噪声的影响抑制高达70dB，从而有效地消除了影响这些噪声源影响相位噪声测量系统的本底噪声。使用 2 公里光子延迟线，我们在 10 GHz 载波周围分别实现了 1 kHz 时为 −126 dBc/Hz 和 10 kHz 时为 −152 dBc/Hz 的相位噪声测量本底，分别比之前的低 15 和 20 dB基于鉴频器的相位噪声测量系统，使用相同长度的光纤延迟和相同的光学和微波组件。 10 kHz 时的本底噪声为 −152 dBc/Hz，比具有 100 倍互相关和不具有互相关的 Keysight E5052B 相位噪声测量系统分别低 8 dB 和 17 dB。如果使用具有较低残余相位噪声或较长光子延迟线的微波移相器，则这种载波抑制系统预计相位噪声本底会更低。