【作者】 黄博；

【导师】 刘文； 迟楠；

【作者基本信息】 华中科技大学 ， 光学工程， 2013， 博士

【摘要】 激增的网络业务需求促使光纤通信迅猛发展，随着光信号传输速率和传输距离要求的不断提高，先进相位调制格式研究受到越来越多学术圈和工业界的关注。相位调制格式具有巨大的优势：不仅接收灵敏度比传统强度调制信号提高3dB，而且在光纤传输中有更大的非线性容忍度，此外，其高阶调制形式四相相移键控（QPSK）降低了信号波特率，减轻对高速电子器件的要求。因此相位调制信号的产生、解调、以及探测技术是关键的研究课题。近些年由于引入光相干探测技术，相位调制格式接收方式更加灵活，利用强大的数字信号处理技术还可以实现光纤传输损伤的补偿。在此背景下，本论文针对光相位调制格式的产生、信号解调和相干探测展开理论和实验研究，概括全文可以总结为以下几个方面：（1）分析了光调制的理论基础，研究了差分相移键控（DPSK）、QPSK、高阶正交幅度调制（QAM）先进调制格式的产生、解调和探测机理。（2）基于马赫-曾德尔延时干涉仪（MZDI）解调DPSK信号原理，提出了联合差分相移键控到双二进制码（DPSK-DB）调制方式应用于40Gb/s长距离接入WDM-PON下行链路传输的方案，利用了DPSK信号长距离传输的优势结合DB信号大色散容忍度和直接探测接收的特点，实现无源光网络中80公里干道传输和5公里接入传输的实验，并演示了基于一个MZDI进行4信道DPSK信号到DB信号的并行转换，节约了系统成本。（3）基于微环谐振腔（MRR）解调DPSK信号原理，提出了一种新型硅基偏振复用差分相移键控（DP-DPSK）解调器件，利用信号模式变换和多模干涉（MMI）结构实现偏振态分离，以及利用一个微环谐振腔实现双偏振态DPSK信号同时解调。首次实验展示了片上80Gb/s DP-DPSK信号的偏振解复用和相位解调。（4）基于相位调制到强度调制的鉴频原理，提出了基于硅基微环谐振腔耦合马赫-曾德尔干涉仪（MRR-MZI）器件产生超宽带（UWB）信号的新方案，该器件具有鉴频响应度高、线性度好的优点。实验演示了由高斯相位调制脉冲通过MRR-MZI器件产生正负极性UWB信号。（5）分析了光相干探测的基本原理和光相干接收机的工作机制，详细论述了不同调制格式信号恢复算法的原理及过程。通过系统仿真评估了QPSK信号恢复算法的性能和受限因素，通过传输实验数据的信号恢复，展示了算法的工作流程和均衡效果。提出了一种新型的级联盲均衡算法，在误差函数中引入相位项使得均衡器具有载波相位恢复的功能，利用最后判决信息来做误差反馈使得该算法与调制格式无关。通过QPSK和16-QAM实验数据的信号恢复证实了该算法的有效性，实验结果表明其恢复性能与经典算法相当。（6）为了提高频谱效率，提出了一种光域超强滤波的Nyquist QPSK方案，并对中间采样点形成的9-QAM信号进行处理，利用提出的一套9-QAM信号恢复算法成功抑制了码间干扰（ISI）效应。11×112Gb/s DP-QPSK25GHz间隔Nyquist-WDM背靠背实验证明该方案在接收光信噪比方面比国际领先方案改善0.5dB。另外进行了3×112Gb/s DP-QPSK信号1120公里光纤传输实验，每信道被压缩至18GHz超窄带宽，信号传输后最小误码率达到1×10^-4更多还原

【Abstract】 The high development of optical fiber communications is excited by the rapidincreasing demand of network services. Advanced phase modulation formats have beenattracting more and more attentions both from academic and industry as the higher bit rateand transmission length are required. The advantages of phase modulation format are: thesensitivity to receive phase modulated signal is superior to traditional intensity modulationby3dB. Phase modulation format can tolerate higher fiber nonlinearity effect in the fibertransmission. The deployment of Quadrature Phase Shift Keying (QPSK) decreases thesignal baud rate and releases the requirement of high speed electronic devices. Therefore,phase modulated signal generation, demodulation, and conversion become very importantresearch issues. Optical coherent detection has made revolutionary progress in recent years.Phase modulation formats are used more widely because the phase signal can be receivedby the coherent detection. Besides the transmission impairments can be compensatedthanks to the powerful digital signal processing techniques.The optical signal generation, conversion and optical coherent detection with respectto the phase modulation formats are theoretical investigated and experimentally studied inthis thesis. The major research achievements and contributions of this dissertation aresummarized as follows:(1) The optics modulation principle is investigated. The generation, demodulation, anddetection of Differential Phase Shift Keying (DPSK), QPSK and high level QuadratureAmplitude Modulation (QAM) are studied.(2) We propose and demonstrate combining DPSK and duobinary (DB) transmissionfor the downstream in40Gb/s long-reach wavelength division multiplexed-passive opticalnetworks (WDM-PONs) in order to provide robust transmission performance in thebackhaul section and simple detection at the Optical Network Units (ONUs). DPSK isdeployed in the trunk span as it provides stronger robustness to fiber nonlinearity. DB isused in the access span where its higher chromatic dispersion tolerance relieves the need fordispersion compensation.4channel all-optical modulation format conversion from DPSKto duobinary is realized in a single Mach-Zehnder delay interferometer (MZDI) in the Remote Node (RN) to decrease system cost.(3) A novel silicon based dual polarization DPSK (DP-DPSK) demodulation device isproposed. The polarization separation is realized based on the mode conversion and themulti-mode interference (MMI) structure. The orthogonal polarization DPSK signals aredemodulated based on only one microring resonator. We first time demonstrate the80Gb/sDP-DPSK polarization de-multiplexing and demodulation on chip.(4) Ultra-wideband (UWB) generation based on the microring-coupled Mach-ZehnderInterferometer (MZI) is proposed. Microring-coupled MZI plays the role of high sensitivelinear discriminator. Two polarity Monocycle pulses are generated from Gaussianmodulated phase signal using silicon microring-coupled MZI device.(5) Optical coherent detection principle and coherent receiver are investigated. Digitalsignal processing (DSP) algorithms for different modulation formats are studied in principleand simulation analysis. The performances of algorithms are presented for the experimentaldata recovery. We propose a novel cascaded adaptive blind equalizers based ondecision-directed modified least mean square (DD-MLMS) algorithm for polarizationseparation and carrier phase recovery. The algorithm is compatible with varioussquare-QAM formats. The experimental results of DP-QPSK and DP-16QAM back-to-backtransmission show that the performance is very close to the general algorithm but with abenefit of the reduced operation complexity.(6) We propose9-QAM data recovery for DP-QPSK signal in presence of strongfiltering to approach Nyquist bandwidth in order to increase spectrum efficiency. Thedecision-directed least radius distance (DD-LRD) algorithm for blind equalization is usedfor9-QAM recovery and inter-symbol interference (ISI) compression.11×112Gb/sDP-QPSK25-GHz spaced Nyquist-WDM experiment result shows optical signal-to-noiseratio (OSNR) tolerance is improved by0.5dB at a bit error rate (BER) of1x10-3comparedto constant modulus algorithm (CMA) plus post-filter algorithm.3×112Gb/s DP-QPSKover1120km transmission is demonstrated. The BER can achieve1×10-4when thebandwidth per channel is strongly compressed to18GHz.更多还原