Research Of Impairment-Aware And Compensating Control Strategy In Optical Network

With the requirement of information communication and the rapid development of Internet technology, the greater challenge to optical network is demanded by business transmission of massive data. The backbone optical transport networks are evolving from traditional network architecture to transparent WDM networks, in order to reduce network operating and bulding cost and achieve efficient, reliable and large size information exchange. Automatic switched optical network (ASON) and wavelength switched optical network (WSON), further integrate the intelligent control mechanism of the control plane and reconfigurable technology of wavelength transmission plane, to achieve a large capacity and end-to-end all-optical communication. Otherwise, in transparent transmission in intelligent optical networks, due to the lack of3R regeneration to physical devices, physical impairments will accumulate along the light path, which may degrade optical signal quality in long-haul transmission systems and make the data unrecognizable at the receiver. Therefore, physical impairments must be considered in optical control plane, in order to guarantee the quality of transmission. The above problems are investigated in depth in this paper with the support of National Natural Science Fund of China, and the research results have be published in Optics Communication and JOAM. The main innovative contributions are listed as follows.Firstly, Flexibility and transparency in Optical network lead to dynamic change of physical impairment, to the flexible and transparent optical network, so the paper considers the thought of adaptive control to support optimal quality to dynamic transmission of end-to-end. It means lead into the control theory and control method makes optical links as the control object, and makes full use of compensation ability of physical impairment to various adjustable equipment of the optical network(such as variable gain optical amplifiers). Meanwhile, it means to achieve dynamic adjustment and optimization of transmission quality to the whole link to meet the transmission requirement with the relevant control strategy and method from the source node to the destination node. It also means to study physical impairment and compensation to the optical link from two aspects of controlling theory to communication. The control theory is applied to the information and the network, and the scope and depth of researching control strategy is extended.Secondly, to optimization of transmission quality to the optical signal, I proposed a self-adjusting parameter controller for power compensation based on the tunable optical devices and transmission impairment aware. The control models based on PD and PID control theory, combined with the advantages of fuzzy control. So the control model could effectively compensate physical impairment of the optical signal with OSNR into transfer function, and achieve dynamic performance adjustment of tunable device to physical impairment compensation of end-to-end in the optical link. In this paper, under the allowable minimum limit of OSNR to simulate it, the OSNR value of optical link at each node can be effectively controlled, especially based on parameter self tuning controller for the whole adjustment results of OSNR are superior to self-tuning controller based on PD control by more than five percent.Thirdly, in the fuzzy control system the prior knowledge are not easy to be obtained before judging control system, and the fuzzy rules are not easy to established. At the same time the three paprameters of PID cannot be changed. So aiming at thedisadvantages of the fuzzy control system, I propose self-tuning PID control model based on BP neural network combining with state information of optical links. The controller calculates the regulation value of the tunable optical devices, and signaling module transmits them to all the nodes via control plane. And each node according to the adjustment value of the tunable optical devices, achieve the transmission quality optimization. The results of simulation based on BP neural network self-tuning PID control compares the outputs with fuzzy adaptive compensation control, because of overcoming the influence of experience of people, the output results relatively smooth and sound. And it shows that the control method is more flexible and effective.Fourthly, based on PID control adjustment model on BP neural network, I consider the working mechanism of the controlled object and the controller to network control system(NCS), and it is inevitable to appear delay time in forward and feedback channel lines, and it may lead to a greater deviation to control system or instable. In this paper, I propose further improvement of the controller to the effects of controller induced delay time during the control process. Time-delay is introduced into OSNR and intersfer function. In the optical link including10nodes, the result of simulation shows output of OSNR is robust without occur ringcontrol shocks. It also shows that under the comprehensivly considering time-delay, neural network controller based on improved PID, can be stably complete the control on impairment compensation.