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    • 92. 发明申请
    • System, Method and Apparatus for Coherent Optical OFDM
    • 用于相干光OFDM的系统,方法和装置
    • US20100329683A1
    • 2010-12-30
    • US12495779
    • 2009-06-30
    • Xiang Liu
    • Xiang Liu
    • H04J14/02
    • H04B10/2513H04B10/548H04J14/002H04L27/2697
    • Digital compensation of chromatic dispersion (CD) effect experienced by optical orthogonal frequency-division multiplexed (OFDM) signal in fiber transmission is provided in the frequency domain using a Fast Fourier Transform/Inverse Fast Fourier Transform (FFT/IFFT) pair with equal length of digital samples prior to OFDM receiver signal processing, wherein the equal length is larger than the length of a FFT used for OFDM subcarrier demultiplexing of the received signal. The OFDM signal processing is independent of fiber CD, so small guard-interval (GI) can still be used to achieve high spectral efficiency even under the experience of large CD. The GI need only to be large enough to accommodate other effects such as polarization-mode dispersion. The length of an IFFT used for OFDM subcarrier multiplexing, as well as the FFT for OFDM demultiplexing can be sufficiently small so subcarrier spacing is sufficiently large to tolerate typical frequency offsets between the transmitter laser and the optical local oscillator.
    • 在频域中使用具有相同长度的快速傅里叶变换/快速傅里叶逆变换(FFT / IFFT)对提供光纤传输中的光正交频分复用(OFDM)信号所经历的色散(CD)效应的数字补偿 在OFDM接收机信号处理之前的数字样本,其中相等的长度大于用于接收信号的OFDM子载波解复用的FFT的长度。 OFDM信号处理与光纤CD无关,因此即使在大CD的经验下,仍然可以使用小的保护间隔(GI)来实现高的频谱效率。 GI仅需要足够大以适应诸如偏振模色散的其他效果。 用于OFDM子载波多路复用的IFFT的长度以及用于OFDM解复用的FFT可以足够小,使得子载波间隔足够大以容忍发射机激光器和光学本地振荡器之间的典型频率偏移。
    • 95. 发明申请
    • SYSTEM AND METHOD FOR RECEIVING HIGH SPECTRAL EFFICIENCY OPTICAL DPSK SIGNALS
    • 用于接收高光谱效率的光学DPSK信号的系统和方法
    • US20100046948A1
    • 2010-02-25
    • US12194241
    • 2008-08-19
    • Andrew Roman ChraplyvyXiang LiuChandrasekhar Sethumadhavan
    • Andrew Roman ChraplyvyXiang LiuChandrasekhar Sethumadhavan
    • H04J14/02
    • H04B10/677
    • Apparatus and methods are provided for receiving differential phase-shift keyed (DPSK) optical signals subjected to tight optical filtering, such as may be experienced by 40 Gb/s and 100 Gb/s channels in a dense wavelength division multiplexing (DWDM) communications system with 50 GHz channel spacing. An optical DPSK receiver is described which employs an optical delay interferometer (ODI) demodulator having a free spectral range (FSR) that is larger than the symbol rate (SR) of the DPSK signal to be demodulated. The receiver includes means for introducing an additional power imbalance between the outputs of the ODI demodulator, and the additional power imbalance may be related to the ratio of FSR to SR. The additional power imbalance increases the signal tolerance to tight optical filtering, thereby achieving high spectral efficiency in applications such as DWDM.
    • 提供了用于接收经受紧密光学滤波的差分相移键控(DPSK)光信号的装置和方法,例如在密集波分复用(DWDM)通信系统中可能经历40Gb / s和100Gb / s信道 具有50GHz信道间隔。 描述了一种光学DPSK接收机,其采用具有大于待解调的DPSK信号的符号速率(SR)的自由频谱范围(FSR)的光学延迟干涉仪(ODI)解调器。 接收机包括用于在ODI解调器的输出之间引入附加功率不平衡的装置,并且附加功率不平衡可以与FSR与SR的比率有关。 额外的功率不平衡增加了对严格光学滤波的信号容限,从而在诸如DWDM的应用中实现高频谱效率。
    • 96. 发明申请
    • System, method and apparatus for channel estimation with dual polarization training symbols for coherent optical OFDM
    • 用于相干光OFDM的双极化训练符号的信道估计的系统,方法和装置
    • US20090324223A1
    • 2009-12-31
    • US12215741
    • 2008-06-30
    • Xiang Liu
    • Xiang Liu
    • H04J14/06
    • H04J14/06H04L25/0204H04L25/022H04L25/0228
    • System, apparatus and method of optical communication are provided for performing channel estimation for an optical OFDM system by utilizing correlated dual-polarization training symbols (CDPTS) to offer high system tolerance to fiber nonlinear effects such as cross-phase modulation (XPM) among wavelength-division multiplexed (WDM) channels. An exemplary method includes receiving a pair of dual-polarization or polarization-multiplexed training symbols in an optical polarization-division multiplexed (PDM) orthogonal frequency-division multiplexed (OFDM) signal, and performing channel estimation to obtain an estimated channel matrix for at least a first of a plurality of subcarriers of the PDM-OFDM signal. Channel compensation is performed based on the estimated channel matrix for at least the first subcarrier of the OFDM signal and symbols then decoded.
    • 提供了光通信的系统,装置和方法,用于通过利用相关的双极化训练符号(CDPTS)来对光OFDM系统进行信道估计,以提供对光纤非线性效应(例如波长之间的交叉相位调制(XPM))的高系统容限 (WDM)通道。 一种示例性方法包括在光偏振分复用(PDM)正交频分复用(OFDM)信号中接收一对双偏振或偏振复用训练符号,并执行信道估计以获得至少至少的估计信道矩阵 PDM-OFDM信号的多个子载波中的第一个。 基于OFDM信号的至少第一子载波的估计信道矩阵进行信道补偿,然后进行解码。
    • 97. 发明授权
    • Data-aided multi-symbol phase estimation for optical differential multilevel phase-shift keying signals
    • 用于光学差分多电平相移键控信号的数据辅助多符号相位估计
    • US07623796B2
    • 2009-11-24
    • US11307899
    • 2006-02-27
    • Xiang Liu
    • Xiang Liu
    • H04B10/06
    • H04B10/66
    • A data-aided, multi-symbol phase estimation (MSPE) scheme is described for improving receiver sensitivity in the direct-detection of optical differential multi-level phase-shift keying (ODmPSK) signals including optical differential quadrature phase-shift keying (ODQPSK) signals, ODQPSK signals with amplitude shift keying (ODQPSK+ASK), optical differential 8-level phase-shift keying (OD8PSK) signals with eight phase levels, and optical differential phase-shift keying signals with more than eight phase levels. The use of data-aided MSPE substantially reduces the “differential detection penalty,” with receiver sensitivity approaching that of coherent detection schemes.
    • 描述了数据辅助的多符号相位估计(MSPE)方案,用于在包括光学差分正交相移键控(ODQPSK)的光差分多电平相移键控(ODMPSK)信号的直接检测中提高接收机灵敏度, 信号,具有幅移键控(ODQPSK + ASK)的ODQPSK信号,具有八个相位电平的光差分8电平相移键控(OD8PSK)信号,以及具有八个以上相位电平的光差分相移键控信号。 数据辅助MSPE的使用大大降低了接收机灵敏度接近相干检测方案的“差分检测损失”。