基于FPGA的实时光OFDM发射机的研究

基于Xilinx现场可编程门阵列(FPGA)实时产生正交频分复用(OFDM)信号,其中包括伪随机二进制序列发生器(PRBS)实现、完全并行运算反傅里叶变换(IFFT)技术的应用以及数模转换(DAC)接口电路的设计等,OFDM电信号解调后的星座图具有较好的收敛性,相应的误差矢量幅度(EVM)为4.42%。当发射机与接收端存在采样频率偏差时,各子载数据产生不同的相位旋转,系统误比特率(BER)显著升高,采样频率同步后系统性能得到明显改善。通过搭建强度调制直接检测光OFDM(O-OFDM)实验系统,传输200km标准单模光纤(SSMF)后,在接收端对O-OFDM信号进行了离线处理,与背靠背(BTB)传输相比,光功率代价小于0.6dB,实验结果表明,所设计的O-OFDM发射机具有较好的性能。

The study of real-time optical OFDM transmitter based on FPGA

The real-time orthogonal frequency division multiplexing (OFDM) signal is generated based on Xilinx field programmable gate array (FPGA),which includes p seudo-random binary sequence (PRBS) ge nerator,inverse fast Fourier transform (IFFT) with completely parallel c omputing technology,and the design of digital-to-analog conversion (DAC) inter face circuit.The constellation of demodulated OFDM signal has a good convergence ,and the corr esponding error vector magnitude (EVM) is 4.42%.Bit error rate is significantly in creased due to the different rotation phases for sub-carriers,when the sampling frequency offset exists between transmitter and receiver,and we get improve d system performance after sampling frequency synchronization.The direct-detect ion optical OFDM experimental system is established,and then the off-line digital s ignal pro cessing after 200km standard single mode fiber transmission is taken.An optica l power penalty of less than 0.6dB is shown,compared with back-to-back (BTB) o peration.The experimental results show that the designed real-time optical OFD M transmitter has good performance.