Research On Optical Fiber Based Stable Radio Frequency Transmission

Stable frequency transmission plays an important role in many applications,such as deep-space network,geodesy,development of next-generation X-ray sources and long baseline coherent radio telescope arrays.The traditional satellite link has been unable to meet the needs of some applications requiring high-precision frequency transmission.Given the advantage of low loss,high reliability and wide bandwidth,optical fiber links have become the best transmission medium to achieve ultra-stable frequency transmission.In order to achieve ultra-stable frequency dissemination,the phase fluctuations introduced by environmental changes should be compensated.This paper mainly studies the technology of fiber-based stable frequency transmission,introduces the general method and main technology of compensating phase drifts in optical fiber link,and focuses on multi-access phase stabilized transmission based on passive compensation method.Multi-access phase stabilized transmission systems can be divided into trunk,star,tree,and ring network structures according to the distribution and the connection status of the receiving nodes.This paper analyzes the characteristics of each network structure and the design of multi-access phase stabilized transmission systems in each network structure.Schemes of multi-access phase stabilized transmission based on passive compensation method with anti-group velocity dispersion(GVD)in truck,star and tree network structures have been proposed.This paper proposes and demonstrates a multi-access phase stabilized transmission scheme based on passive compensation method with anti-GVD and anti-backscattering function.In this scheme,the phase jitter of the radio frequency signal can be automatically compensated by passive frequency mixing,and phase stabilized signals can be obtained at any point along the trunk optical fiber link.In order to suppress the effect of GVD and Rayleigh backscattering,signals with the same optical wavelength and different electrical frequencies are transmitted back and forth in the optical fiber link.In the experiment,a 2.4 GHz signal is transmitted to the intermediate node and the remote node within 50.2 km single-mode optical fiber,and the intermediate node is 10 km away from the central station.After compensation,the root mean square phase jitter of the signals is no more than 0.031 rad at the two receiving nodes,the phase jitter of the transmission signals can be effectively compensated.