Performance of CO-OFDM system with RS-Turbo concatenated code

In this paper, the RS-Turbo concatenated code is applied to coherent optical orthogonal frequency division multiplexing (CO-OFDM) system. RS(186,166,8) and Turbo code with code rate of 1/2 are employed for RS-Turbo concatenated code. Two decoding algorithms, which are Max-Log-MAP algorithm and Log-MAP algorithm, are adopted for Turbo decoding, and the iteration Berlekamp-Massey (BM) algorithm is adopted for RS decoding. The simulation results show that the bit error rate (BER) performance of CO-OFDM system with RS-Turbo concatenated code is significantly improved at high optical signal to noise ratio (OSNR), and the iteration number is reduced compared with that of the Turbo coded system. Furthermore, when the Max-Log-MAP algorithm is adopted for Turbo decoding, the transmission distance of CO-OFDM system with RS-Turbo concatenated code can reach about 400 km without error, while that of the Turbo coded system can only reach about 240 km when BER is lower than 10-4 order of magnitude.     

Research on the transmission performance of turbo codes in DDO-OFDM system

With the rapid development of optical elements with large capacity and high speed,the network architecture is of great importance in determing the performance of wavelength division multiplexing passive optical network(WDM-PON).This paper proposes a switching structure based on the tunable wavelength converter(TWC)and the arrayed-waveguide grating(AWG)for WDM-PON,in order to provide the function of opitcal virtual private network(OVPN).Using the tunable wavelength converter technology,this switch structure is designed and works between the optical line terminal(OLT)and optical network units(ONUs)in the WDM-PON system.Moreover,the wavelength assignment of upstream/downstream can be realized and direct communication between ONUs is also allowed by privite wavelength channel.Simulation results show that the proposed TWC and AWG based switching structure is able to achieve OVPN function and to gain better performances in terms of bite error rate(BER)and time delay.