| With the rapid growth of broadband services in optical networks,such as high-definition video,data centers,interactive games,cloud computing and other services,resulting in an increasing demand for optical network bandwidth.This growing bandwidth demand has brought severe challenges to the development and expansion of optical networks,and only through the increase of optical network transmission capacity cannot achieve the efficient use of the spectrum in optical networks.The wavelength division multiplexing(WDM)spectrum optical transmission network is divided into a fixed bandwidth,such as 50 GHz or 100 GHz,the bandwidth of each width represents a light path,and the center and the size of each spectrum bandwidth is fixed,the fixed optical path division can easily lead to spectral bandwidth waste.As a result,optical networks need to support multi rate services and support efficient spectrum allocation.With the development of orthogonal frequency division multiplexing(OFDM),the optical network can be more fine-grained division of spectrum resources(such as 12.5GHz,6.25 GHz or smaller),according to the size of the service request for the spectrum allocation of the spectrum resources.At the same time,with the introduction of the concept of software definition to the optical network,it makes the optical network to be flexible,programmable and intelligent.So the software defined elastic optical networks is the direction of the next generation optical networks.With the emergence of mixed line rate in optical networks,different rate signals in optical networks can be simultaneously in the same optical fiber transmission,which will be a serious physical impairment among adjacent channels with different modulation formats,especially the cross phase modulation(XPM).Physical layer impairments in optical networks is an important factor in the deterioration of optical signal transmission of quality(Qo T),the influence degree and the interval between different data transmission rates and different rate signals are closely related,which severely limits the flexibility of software defined multi speed transmission network technology in optical network to improve network efficiency.At the same time,with the division of the spectrum more fine-grained,the spectrum consistency constraint and the spectrum continuity constraint are more strict in the process of spectrum allocation process.In this paper,in-depth study of software defined flexible optical network physical layer impairment aware(IRSA),in order to ensure the Qo T of service and improve the network performance.The main research results are as follows:In the background of the elastic optical networks,a novel spectrum partition and topology plane RSA algorithm is proposed.The algorithm considers the XPM impairment under the multi rate coexistence of flexible optical network and proposes the strategy of spectrum partitioning.By increasing the physical distance between the optical channels at different rates,the effect of XPM is reduced in some degree.On this basis,the topology of the network is abstracted into a number of sub topologies,which can solve the limitation of spectrum consistency constraint and spectrum continuity constraint.The proposed algorithm not only can solve the spectrum consistency and spectrum continuity constraints,but also meet the needs of the service Qo T,and reduce the traffic blocking probability.Aiming at the problem of the routing and spectrum assignment of cross phase modulation in software defined elastic optical networks(SD-EONs),the routing and spectrum allocation algorithm based on Open Flow is proposed.By adding the spectrum partition module and extended Open Flow protocol in SD-EONs Open Flow controller,different rates of traffic in the network are allocated to different spectral regions,increasing the low rate channel spacing between the business and the high rate of business,in order to reduce cross phase modulation impairment and improve the utilization rate of resources. |
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