介绍了基于XI LI NX FPGA的1Gb/s光OFDM(O-OFDM)发送端信号处理的整体设计,对传输信号的星座映射及FFT进行了研究,重点分析了不同量化比特数时IFFT/FFT的误差矢量幅度(EVM),提出了使用不同量化比特对信号进行适当放大而提高系统的IFFT-FFT转换精度的方法。实验验证了OFDM信号I FFT-FFT变换后随量化比特数的增加,EVM值不断减少,相应的星座图更收敛。
A novel dual polarization differential quadrature phase shift keying （DP-DQPSK） system is proposed, whose receiver is the same as the single polarization DQPSK system, while it does not need polarization de-multiplexing like the conventional polarization division multiplexing QPSK （PDM-QPSK）. Polarization mode dispersion （PMD） is mainly considered and PMD compensation for the DP-DQPSK system is studied. As the feedback signal for PMD compensation, the degree of polarization of the signals is discussed in detail. The results show that PMD tolerance can be improved by 89 ps within 1 dB optical signal noise ratio penalty after PMD compensation for the DP-DQPSK system.
We experimentally investigate the transmission performance of 60-GHz signals over standard single-mode fiber （SSMF） and wireless links at different bit rates. Experimental results show that in a transmission of over 10-km SSMF and 1.3-m wireless link, bit rate reaches up to 5 Gb/s and bit error rate （BER） is less than 10-4 . The main limiting factor in such radio-over-fiber （ROF） systems is intersymbol interferences caused by the so-called walk-off effect when BER is below 10 8 . In addition, a transmission of over 20-km SSMF without chromatic dispersion compensation is briefly investigated. For a BER of 10 8 , the optical penalty is 2 dB.
