光纤稳相微波频率传输中相干瑞利噪声的影响与抑制

利用光纤进行相位稳定的微波频率参考的远距离分配,在深空科学研究、基础物理测量以及多基地雷达技术方面有着广泛的应用需求。研究了基于往返相位校正的光纤稳相传输理论,建立了稳相传输的理论模型,搭建了基于光电延迟锁相环的光纤稳相传输实验系统,理论分析并实验研究了相干瑞利散射噪声对系统传输相位稳定性的影响。研究发现相干瑞利散射噪声不仅直接造成远端信号信噪比恶化,并且通过锁相环路转化为系统残余相位噪声,进一步恶化远端信号的稳定性,成为影响稳相传输系统性能的主要因素。针对该问题,提出了双波长的稳相传输技术,有效地克服了相干瑞利散射噪声的影响,实现了10GHz微波频率参考、100km光纤稳相分发,传输至远端的相位均方根抖动(RMS-jitter)低于730fs。

Influence and Suppression of Coherent Rayleigh Noise in Fiber-Optic-Based Phase-Stabilized Microwave-Frequency Transmission System

Distribution of phase-stabilized microwave frequency reference over a wide area is a key technology in a variety of applications including long-baseline interferometry for radio astronomy, fundamental physics metrology and multi-static radar system. Based on the round-trip phase correction, a theory model of phase-stabilized microwave frequency reference distribution through optical fiber with opto-electronic delay locked-loop is established. Theoretical and experimental efforts are made to investigate the influence of the coherent Rayleigh-scattering noise on the system stability. Coherent Rayleigh-scattering noise not only leads to degradation of signal-to-noise rotio, but also further degrates the stabiling of remote signal by transforming phase locked loop into residual phase noise, which is the key factor of phase-stabihzed transmission. A dual wavelength transmission technology is proposed to overcome its influence, the concept by transmitting a 10 GHz microwave frequency reference over 100 km single-mode fiber is demonstrated, and the root mean square-jitter is measured under 730 fs at the remote end.