Research On Replacement Strategy For Ultra-low Loss Fiber Links In Elastic Optical Network

The lifespan of an optical fiber is typically from 20 to 25 years.The lifetime of a large number of fiber links laid in the 80 s and 90 s of the last century are about to expire,so in the next few years,they face the situation of upgradation.Ultra low-loss fiber(ULL)is considered to be a new type of fiber to be used for large-scale deployment due to its excellent transmission performance.However,for a large-scale network,due to the limited human resources,it is generally unrealistic to upgrade all the old optical fibers that have been laid down to ultra-low-loss optical fibers at one time.Network operators prefer to gradually upgrading these old optical fibers.Therefore,it is necessary to consider a suitable upgradation strategy in order for good network performance in the course of fiber upgradation.This thesis focuses on the ULL fiber upgradation strategy based on Elastic Optical Network(EON).First,for the scenario of static demand,we propose three ULL fiber upgradation strategies,namely,the PL,Random,and LC strategies.With the consideration of 1+1 path protection,we solve the routing,modulation and spectrum assignment(RMSA)problem for the EON by developing a mixed integer linear programming(MILP)model and proposing a spectrum window plane(SWP)based heuristic algorithm.The studies show that under a certain fiber upgradation ratio,the LC strategy is the most efficient to perform close to the MILP model and it can always outperform the other two strategies.In addition,when all the fiber links are upgraded with ULL fibers,a saturation phenomenon is observed that when the attenuation coefficient of ULL fibers has been low enough,further reducing it will not lead to a further improvement of spectrum utilization.Second,for the scenario of dynamic traffic demand,we also propose three upgradation strategies,including the OB,PL and SRT strategies.The SWP-based heuristic algorithm is extended to provision dynamic lightpath services.The studies show that under a certain fiber upgradation ratio,the OB strategy can always achieve a network bandwidth blocking probability(BBP)lower than the other two strategies.Moreover,when all the fiber links are upgraded with ULL fibers,a saturation phenomenon is observed that when the attenuation coefficient of ULL fibers has been low enough,further reducing it will not lead to further reduction in the network BBP.