We propose a novel and simple all-optical 160-Gb/s orthogonal frequency division multiplexing（OFDM） symbol generator which is based on discrete triangle waveform driving-LiNbO_3 modulators to realize large-range linear optical shift.The entire system needs 64 discrete modulators：at the transmitter,a 2.5-Gb/s optical duobinary（ODB） modulator for data modulation and a 2.5-Gb/s triangle waveform driving-LiNbO_3 phase modulator for phase shift to generate each subcarrier;and at the receiver,a 2.5-GHz optical band pass filter（OBPF） using Faraday anomalous dispersion optical effect to separate them.Excellent bit error rate（BER） is observed after 1060 km of transmission without any dispersion compensation.
The analytical expression of bit error probability in a balanced differential phase-shift keying(DPSK) optical receiver considering nonlinear phase noise and EDFA ASE noise is given,which is very useful to estimate the performance of DPSK balanced and unbalanced receiver in optical communication system.Through analysis,if only nonlinear phase noise is considered,both the balance and unbalanced receivers have the same performances.But if adding the ASE noise of EDFA,the balanced receiver is better.
Experimental implementations of continuous optical time domain Fourier transformation based on time lenses and optical orthogonal frequency-division multiplexing （OFDM） system are carried out. Such a system is verified through 100-kin transmission of 10-Gb/s non-return-to-zero （NRZ） intensity-modulated direct-detection （IM-DD） without any dispersion compensation. The system＇s bit error rate （BER） and power penalty are 10 12 and 4 dBm, respectively.
A novel method for distortion-free optical pulse transmission is theoretically proposed and simulated, in which two time lenses formed by dispersion fibers and quadratic phase modulations are utilized. One is used as an optical inverse Fourier transformation （OIFT） device to transform the initial time-domain data to frequency-domain one at the transmitter and the other as an optical Fourier transformation （OFT） device to recover the data at the receiver. By using the unchanged spectral envelope in linear optical fiber communication, the initial data can be recovered. Through simulations, a 10× 100 Gb/s intensity-modulated direct-detection （IM-DD） dense wavelength division multiplexing （DWDM） system over 20000 km transmission without the compensation for polarization mode dispersion （PMD） and dispersion slope is achieved, which can be used to upgrade the current 100Gb/s IM-DD system to a 100-Gb/s one directly.
研究了IP over WDM网络中IP业务流量的突发性对底层光脉冲传输的影响。突发的IP业务流量使WDM网络中传输信号的信道数目服从泊松分布,在非线性薛定谔方程(NLSE)的基础上进行IP流量分析,通过数值计算,考查了IP业务流量对四波混频(FWM)和交叉相位调制(XPM)的综合影响,得到了不同输入光功率、不同流量负荷下的眼图。结果表明,40信道的WDM网络中,当输入信号光功率大于5 dBm时,IP流量负荷的改变将会对网络性能产生剧烈的影响。同时,通过公式计算出FWM功率、比特误码率与输入光功率、流量负荷、信道间隔的关系,突出强调了不同信道分布对探测信道FWM效应的不同影响。
