Research On Dissemination Technologies Of Stable Radio Frequency Over Optical Network

With the development of atomic clock and optical clock technologies,the stability of frequency reference standards generated by clock sources has approached the level of 10-18.Realizing the transmission of these stable radio frequency(RF)references plays an important role in many advanced fundamental scientific applications and infrastructures such as atomic clock comparison,deep space exploration,aerospace,and positioning and navigation.However,the traditional microwave or satellite transmission link is influenced by the fluctuation of the atmospheric environment,and the stability of reference standards can only reach the level of 10-15/day,which cannot meet the transmission requirements of high-precision RF reference.A feasible solution is to use optical fiber as the transmission medium,the transmission stability requirements of RF reference can be fully satisfied due to the optical fiber has advantages in low attenuation,high stability,and anti-electromagnetic.Nowadays,the fiber-based frequency dissemination network is evolving from simple point-to-point transmission systems to complicated point-to-multipoint dissemination network after the fiber-based frequency dissemination schemes are fully demonstated.The transmission distance and range are gradually expanding.Hence,constructing the fiber-based point-to-multipoint dissemination network has great significant to economic and social development and national defense.Hower,if we adopt the scheme to constructing fiber-based RF reference dissemination network with laying the entire new fiber links,which will lead to high project expense、unbearable long schedule.One possible solution is to construct the RF reference dissemination network based on the optical wavelength resources and infrastructures in telecommunication network.However,the process of hybrid network is hindered by the differentces in node structures and amplication ways.Therefore,the technologies of constructing the dissemination network in telecommunication network are need to be deeply research.This paper focuses on how to construct and optimize the RF dissemination network over the telecommunication network.The main research results of this paper are summarized as follows:1)This paper studied the possible transfer scheme and phase compensation method when constructing the hybrid network.First,we analyzed the necessity of relatizing the hybrid network,and the promotion for each kind of individual network is summarized.Then,the differences in network node and the amplification structure between RF reference network and telecommunication network are pointed out.In order to overcome these diffcults,this paper innovatively proposed the hybrid dissemination network scheme and dual-probe passive phase compensation method(DPPCM).The general network node and amplication node can be realized by using the technologies of DWDM and ROADM in hybrid dissemination network,and the phase noise introduced by the fiber links can be cancelled by DPPCM.The RF reference and telecommunication traffic can be transferred togther over the hybrid dissemination network at the same time.We take the simulations to verified the performance of hybrid dissemination network scheme and DPPCM over different ring network.Simulation results confirm that the DPPCM can achieve the stability of 1.36× 10-13/s and 3.26×10-17/10000s in 1 60km+80km hybrid dissemination network、1.42 × 10-13/s and 2.08 × 1 0-17/104s in 120km+120km hybrid dissemination network.2)This paper studied the optimization problem of amplification site location.When constructing the hybrid dissemination network over the wide area telecommunication network,plenty of amplifiers are need to place along the long fiber links to compensate for the power loss of RF reference.However,the amplifiers will introduce the ASE noise,which will degrade the stability of RF reference.Therefore,how to reduce the influences of ASE noise by optimizing the location of amplification sites in hybrid networks is an urgent issue that needs to be addressed.In this paper,we proposed the hybrid dissemination network scheme for wide area network(WAN)based on an improved dual-probe passive compensation method.Then,the objective function and power constraints are summarized.In order to find the proper solution for the optimization problem,we proposed as maximum as possible placement strategy(AMAP),as compatible as possible placement strategy(ACAP),and as average as possible placement strategy(AAAP).The performance of AMAP,ACAP,and AAAP strategies are verified in different ring networks based on China Optical Fiber Backbone Network.3)This paper studied the network planning of RF dissemination network in large scale distributed applications.At present,the point-to-multipoint RF dissemination network is limited by network structure and phase compensation method,which can not meet the requirements of the large-scale distributed networks.In order to overcome this drawback of point-to-multipoint RF dissemination network,we propose the cascaded tree RF synchronization network scheme based on the traditional tree RF transmission scheme.The phase noise introduced by optical fiber links is compensated by round-trip passive phase compensation method.The cascaded tree synchronization network can satisfy the needs of lagre-scale distributed network.Howerver,due to the large number of access sites in large-scale distributed applications,the phase noise introduced by ground group velocity dispersion(GVD)and ASE noise will increase.,which will accelerate the speed of deteriorating the stability of RF reference.Therefore,how to constructing the cascaded tree synchronization network with minimum total phase noise is an urgent problem that needs to be solved.In this paper,we formulated the noise model of cascaded tree synchronization,and the objective function and constraints are analyzed.Finally,we proposed the optimal cascaded tree network synchronization algorithm(ONSA)to solve this problem.We take the simulations to verify the performance under different large-scale distributed networks based on Chinese Optical Fiber Backbone Network.Simulation results reveal that ONSA can not only achieve the best performance but also have the largest coverage.