Forward Error Correction (fec) In Optical Communication Networks And Fec Performance Tests

"Forward Error Correction—FEC" was a technique of G707 and G709 agreement which was put forward by the ITU-T. The application of this coding in optical fiber communication system, mainly solved the problem of optical fiber dispersion caused by long distance or super long distance, and the big capacity DWDM; signal fading caused by the long distance delivery; channel noise and the decline of the function of system caused by the interference among several wave-lengths in one optical fiber, efficiently raised the credibility of the signal in the system, prolonged the distance of delivery. The FEC technique is to join the redundancy correct code into the transmission code to lower the margin of the OSNR of the receiver, and to reduce the power that the blast-off needed.This text firstly introduced the development process and the applied background of the FEC, then put forward the transmission quality problem which was caused by the error code in the optical fiber communication system. The error code was caused by the capability decline of the parameters in light guide cable link function, especially in optical cable descend.We met the problem in the optical communication system of China Unicom in our daily work. This text put forward the way of resolving that problem from the theories, then introduced the basic principle, the coding and translate code process of the FEC technical. Next, it introduced the characteristics and the function of three familiar kinds of FECs. Then studied and argued from the theories the theories research and the analysis of the function improvement degree in the system, and in practice, on network chose Zhengzhou to Wuhan segment as the experiment segment built the experiment environment, actually, it proved that on the practical network the function of FEC technique of Siemens company can meet the request of the optical communication system.When confirmed the function of FEC technique of Siemens company can meet the request of the system, it put forward the network optimization scheme to use the FEC technique to resolve the problem—the enlarge of the descend in light guide cable link which existed in the network of optical communication system of China Unicom, and then made the scheme come true. Through a series of network optimization scheme, availably improved the Q value of the Dense Wavelength Division Multiplexing system and the margin of the Optical Signal to Noise Ratio of China Unicom; solved the problem of parameter descend in light guide cable link on the network in the optical communication system; improved the quality of the transmission signal; saved a huge sum of expenses from replacing circuit fiber optic cable and equipments so as to come to the purpose of economizing the cost, and finally verified this text a research of actual meaning in practice.