Research On Application And Performance Of Pon Fiber-fault Monitoring Technology Based On Optical 2D-coding

In recent years,passive optical network(PON)has been considered for network operators to be the best choice of next-generation broadband access solution.It was reported that the majority of the operation and maintenance expense is on monitoring link faults.In addition,monitoring significantly reduces the capital and operation expenditures(CAPEX and OPEX)for both the network provider and the customers.Several fiber-fault monitoring schemes based on traditional OTDR technique have been proposed for monitoring fiber-link in PONs.However,it is difficult for network manager to distinguish in which fiber-link the fault occurs in a tree-topology PON.Thus,some schemes based on optical coding technique have been proposed to overcome the OTDR disadvantages in monitoring point-to-multipoint networks.Thus,some optical coding schemes have been proposed recently for centralized optical fiber in-service monitoring system.In this paper,we researched the applications and characteristics of 2D optical coding fiber fault monitoring technology.Firstly,a novel fiber-fault polling monitoring scheme using optical 2D-pre-coding technique for passive optical networks is proposed.This scheme contains Probe Pulse Pre-coding module,Link Failure Recognition module and Decoder module.We adopt an effective polling monitoring strategy to improve the detection decision probability.The main contents of the performance analysis are as follows:signal-to-noise ratio and signal-to-interference ratio analysis,optimal decision probability and decision threshold analysis,2D codewords construction and codewords characteristic analysis,user geographical distribution and codeword allocation mechanism.Secondly,a mathematical model for optical 2D-coding monitoring system in PONs is developed,then,the system response function,the partial interference probability,SNR and SIR are derived.In simulations,we investigated the impact of the different values of the network sizes,the client separation distances,the transmitted pulse width and the transmitted pulse powers on the SNR,SIR and the relationship of both of them.The suitable system variables can be chosen optimally to facilitate optimal decision,which hence reduce the overall cost of the monitoring system and increase the efficient of fiber fault identification.Then,a novel codeword assignment scheme for the double-length MLMW-OOCs(Multiple Length Multiple Wavelength Optical Orthogonal Codes)is proposed to reduce the effect of interference as well as improve the performance of monitoring system.A construction method of the double-length MLMW-OOCs is introduced,and then a codeword assignment scheme is proposed by considering user geographical distribution to minimize the inter-user interferences.The main idea behind the assignment scheme is to prioritize the short codewords to those users that are close to each other in distance.The extensive simulation results show that compared to 2D-OOC coding scheme,our proposed scheme can support the monitoring of high-capacity PONs with shorter code length to reduce cost and smaller correlation distance to reduce interference,and better SIR performance.Finally,the simulation platform of PON link fault monitoring performance based on 2D optical coding is developed.The platform is composed of fully visualized user interface,monitoring system parameters,system performance analysis and optimal decision performance analysis.The simulation results show that the simulation platform can get the optimal system parameters,and provide the theoretical basis for the practical application of the monitoring system.