Researches On The Super Forward Error Correction Concatenated Code For Optical Transmission Systems

Forward Error Correction(FEC) technology is to detect and correct the error by adding a small mount of redundant information, then it can reduce OSNR tolerance of the receiver, improve the BER of system, improve system reliability, extend distance of the transmission and lower the system cost. So it is widely used in the optical transmission system.As the development of the technology in optical communication system, the further improvements of the transmission rate and distance are heavily limited due to the accumulated optical effects such as the dispersion and Polarization-Mode Dispersion (PMD) and the accumulated nonlinear optical effect in transmission optical fibers. As a result, it has been becoming necessary to develop the novel more powerful Super Forward Error Correction code type in order to gain the higher Net Coding Gain (NCG) and the better error-correction performance to meet the requirements of the rapid development for optical communication systems, compensate for serious transmission quality degradation and avoid using the dispersion-compensating technologies to need the expensive and complex devices and so forth. In the implementation of programs of the super FEC, because of concatenated codes with strong ability of correcting burst and random error, so it is the major object of study of efficient coding in the optical transmission system.The Super-FEC coding technology is one of the main study in the National Key Science of 2003 and Technology Development Program of China (863 Program)―optical fiber communication technology innovation‖. This subject is researched under the condition of taking the National―863‖Key Item of China (Grant No. 2A001AA122012) of the Research and Implementation of the Ultra Long-Haul Wavelength-Division Multiplexing (WDM) Optical Communication Technologies as its application background.This article is for the super type of FEC code.The main achievements of this dissertation are as follows:Firstly, depending on software simulating by Optisystem, we make an analysis of the noise in optical communication system. After that AWGN channel model (namely, Additive White Gaussian Noise channel model) of optical communication systems is established. And then we also analyze the types of error in the AWGN channel. Based on above analyses and the performance analyses of the FEC code types, the main construction method of the FEC code types for optical communication systems are proposed. In the structural pattern and error correction performance, we analyze the related theories of linear block codes, cyclic codes and BCH codes and RS codes.Secondly, we introduced the origin of concatenated codes, the code pattern of various concatenated codes, redundancy and error correction performance. By contrast, we proposed that adding interleaver and iterative decoding of concatenated codes is one of the best programs to improve the existing type of error correction concatenated codes.Thirdly, the main construction methods of the FEC code type for optical transmission systems have been proposed and a novel super forward error correction (Super-FEC) concatenated code of RS(255,239)+ BCH(2040,1930) to be applied for optical transmission systems has been constructed after the characteristics of the concatenated code for optical transmission systems and the two super forward error correction(Super-FEC) code types in ITU-T G.975.1 were analyzed. The simulation results show that this novel concatenated code, compared with the RS(255,239)+CSOC(k0/n0=6/7,J=8) code in ITU-T G.75.1, has a lower redundancy and the better error-correction performance, furthermore, its net coding gain(NCG) is respectively 0.45dB, 0.48dB more than that of BCH(3860,3824)+BCH(2040,1930) code and RS(255,239)+CSOC(k0/n0 =6/7, J=8)code in ITU-T G.975.1 and 2.81dB more than that of RS(255,239) code at the third iteration for the bit error rate (BER) of 10-12. Therefore, the novel Super-FEC concatenated code can better be used in ultra long-haul, ultra large-capacity and ultra high-speed optical transmission systems. Furthermore, the design and implementation of this super FEC code in the optical transmission systems are probed.