【作者】 李超；

【导师】 余少华；

【作者基本信息】 华中科技大学 ， 物理电子学， 2015， 博士

【摘要】 过去近四十年光纤骨干网传输容量增长为每十年超过1000倍,即便如此仍不能满足互联网和宽带无线移动通信爆炸式增长的需求。为了攻克上一代光纤通信中谱效率低、非线性和色散严重等科学问题,本文提出在超大容量光传输系统中采用正交频分复用(OFDM)作为基本创新手段。OFDM技术是把高速串行数据流转换成若干正交的低速数据流,由于其频谱利用率高、抗光纤色散好、抗干扰能力强、计算复杂度低等优点,已作为国际上超大容量光纤通信的热点技术。针对以上科学问题,本文开展了系统深入的理论与实验研究,探索了100-Gb/s超低成本的直接检测方案、1-Tb/s超10,000km标准单模光纤(SSMF)传输相干系统实验、硅基光波导作为波长转换器的超大容量调制格式实验、强度导频补偿CO-OFDM系统发射端IQ不平衡和激光器相位噪声实验、偏振不敏感型、消除泵浦相位噪声的相位锁定双泵浦超大容量波长转换实验、超大容量光纤传输调制后信号边模抑制实验以及C+L波段超大容量相干光传输实验等。主要创新点如下：(1)针对当前国际上100G相干系统用于城域网中成本过高,以及接收端一个40GHz电器件带宽难以接收100-Gb/s光信号的热点问题,本文提出100-Gb/s单PD(光电检测二极管)接收载波共享且保护间隔共享的直接检测光OFDM (DDO-OFDM)传输系统方案,通过实验解决了100G非相干系统中40GHz电带宽PD同时接收100-Gb/s光信号的难题,实验结果表明SSMF传输距离达到880km, PD数从当前商用相干系统的8个减少到1个,ADC(模数转换器)个数从4减小到1。(2)针对Ker}线性效应制约超长距离光纤传输,以及当前国际前沿实验SSMF最高水平为1.15-Tb/s传输10,000km(2011年,美国NEC实验室)的现状,本文提出一种特色奇偶校验码(LDPC)和离散傅里叶变换扩频(DFT-S)调制技术相结合的CO-OFDM方案。实验结果表明,该方案有效地降低了LDPC编码的1.031-Tb/sDFT-S OFDM8-PSK信号光纤传输中Kerr非线性效应的影响,SSMF传输距离从10,000km达到了12,160km,接收机灵敏度从20%FEC解码门限0.02提高到了0.07。(3)当前国际上硅光器件因低功耗低成本、高非线性效应和易于集成等特点成为热点方向,针对其中超大容量光纤传输谱效率难以进一步提升,以及当前国际前沿利用硅基光波导作为波长转换器实验最高水平为16-QAM(2014年Optics Express发表,加拿大麦吉尔大学)的现状,本文结合硅基波长转换实验中需解决的高阶调制问题(如128-QAM),提出了一种利用硅基光波导的OFDM128-QAM波长转换方法,实验在国际上实现了从单载波16-QAM调制向具有低OSNR代价的OFDM128-QAM高阶调制格式的突破。(4)针对国际上超大容量CO-OFDM系统中普遍存在的IQ不平衡(IQ imbalance)问题,本文提出频域二阶矩估计(F-SOME)算法,巧妙地利用强度导频方法同时补偿发射端IQ不平衡和激光器相位噪声,解决了CO-OFDM4-QAM实验系统中发射端IQ不平衡问题。本文17-Gb/s DSB OFDM4-QAM实验结果表明,基于F-SOME的补偿算法可使接收机灵敏度提高1.2dB。(5)针对波长转换中输入信号光和泵浦光FWM后相位噪声转移到转换信号中,严重影响转换信号性能的问题(尤其是在高阶调制的相干光通信中),本文在国际上提出一种偏振不敏感型、消除泵浦相位噪声的相位锁定双泵浦AOWC方案,实验解决了高阶调制偏振复用CO-OFDM系统中转换信号相位噪声剔除的问题,92.9-Gb/sPDM-OFDM32-QAM和557-Gb/s PDM-OFDM8-QAM两种实验结果表明,转换信号OSNR代价均小于1dB,557-Gb/s是目前国际上这一实验的最高速率。(6)针对超大容量光纤传输系统发射端muli-band经OFDM调制后信号边模抑制比(SLSR)过低,导致符号间串扰(ISI)和载波间串扰(ICI)过大以及电信噪比(SNR)下降等问题,本文提出基于数字脉冲成型技术的偏置正交幅度调制OFDM (OFDM/OQAM)方法,从实验上基本解决了ISI和ICI过大的问题。实验结果表明,该方法所实现的OFDM/OQAM信号功率谱密度(PSD)从传统OFDM的15dB提升到35dB,而且在multi-band DDO-OFDM系统中SNR从17.37dB提高到18.56dB。(7)网络干线传输容量是衡量一个国家网络承载能力的关键性指标。本人(排2,共7人)与课题组同事合作完成了C+L波段DFT-S PDM-OFDM128-QAM调制的100.3-Tb/s (375×267.27-Gb/s)信号80km SSMF超大容量传输系统实验,刷新了我国超大容量传输系统实验最高纪录,该成果入选由两院院士选出的2014年中国10大科技进展新闻(位列第八)。更多还原

【Abstract】 The fiber-optic transmissions have increased in capacity by more than one thousand times per ten years sice the past forty years. However, it can not meet the demand on the explosive growth of internet and broadband wireless mobile communication. In order to conquer the scientific issues of low spectral efficiency, serious fiber nonliearity and dispersion in the last generation fiber-optic communication, in this dissertation ultra-large capacity fiber-optic transmission system with orthogonal frequency division multiplexing (OFDM) as the basic method of innovation is proposed. OFDM is a technology that converts higher rate serial data stream into multiple orthogonal data streams with lower rate relatively. Due to its intrinsic advantanges such as high spectral efficiency, robust tolerance against fiber dispersion, robust anti-jamming, low computation complexity and so on, OFDM has been widely researched and used in ultra-large capacity fiber-optic transmission system as a novel and hot technology.To address the above scientific issues, this dissertation carries out systematic and in-depth study. It researches on the application of optical OFDM technology for the related fields in fiber-optic communications, e.g.100-Gb/s low cost direct detection scheme, experiment of1-Tb/s coherent optical signal transmitted over more than10,000km, experiment of wavelength conversion of high order modulation formats using silicon waveguide wavelength converter, experiment of joint compensation of transmitter IQ imbalance and laser phase noise using intensity pilots in CO-OFDM system, experiment of polarization insensitivity pump phase noise cancelled ultra-large capacity wavelength conversion and experiment of C/L-band ultra-large capacity coherent optical signal transmission. The main works and research achievements of this dissertation are summarized as follows:Firstly, to address the hot issue that using current100G coherent detection system in metropolitan area networks leads to high cost and single electrical device with40GHz bandwidth at the receiver could not detect the100-Gb/s optical signal simultaneously, a novel guard-band-shared single-PD direct detection optical OFDM (GBS-DDO-OFDM) scheme is proposed in this dissertation to receive100-Gb/s signal simultaneously. The issue of receiving100-Gb/s signal by one40GHz PD at the same time in non-coherent system is sloved through experiment. The experimental results indicate that the transmission distance over880km SSMF is achieved, the numbers of PDs is decreased from8in current commercial coherent system to1in this scheme, and the numbers of analog-to-digital converter (ADC) is reduced from4to1.Secondly, to address the issue that Kerr nonlinear effect limits the ultra-long-haul fiber transmission reach and the present situation that the reported longest1Tb/s-class transmission is1.15-Tb/s signal over10,000km SSMF in2011accomplished by American NEC lab. A CO-OFDM scheme combined with a kind of characteristic LDPC code and DFT-S technology is proposed in this dissertation. The experimental results show that this scheme can effectively reduce the Kerr nonlinear effect influence in LDPC coded1.031-Tb/s DFT-S OFDM8-PSK signal transmission system. Compared with NEC lab’ work, the transmission distance over SSMF is enhanced from10,000km to12,160km in this scheme. Also, the receiver sensitivity is improved from BER level of0.02(20%FEC limit) to0.07.Thirdly, currently silicon device is becoming a hot research direction in international due to low cost low power consumption, high nonlinear effects and easy to be integrated. To address the present situation that the spectral efficiency of ultra-large capacity transmission is hard to further improve and the highest modulation format used in silicon-based wavelength conversion is16-QAM, a novel wavelength conversion scheme based on silicon waveguide is proposed to slove the issue of OFDM128-QAM signal conversion. The observed constellations in the experiment reveal the impressive on-chip OFDM128-QAM wavelength conversion performance with low OSNR penalty.Fourthly, to address the ubiquitous issue of IQ imbalance in ultra-large capacity CO-OFDM tramsmission system, a frequency domain second moment estimation algorithm (F-SOME) is proposed for the first time in this dissertation. The designed intensity polits can jointly compensate the transmitter IQ imbalance and laser phase noise. The experimental results of17-Gb/s DSB OFDM4-QAM signal indicate that1.2dB receiver sensitivity is improved after F-SOME algorithm compensation.Fifthly, to address the issue that phase noise of input signal and pumps transfers to converted ilders and severely affects the system performance, a polarization insensitivity pump phase noise callanced coherent dual-pump scheme is proposed in this dissertation. The experimental results of92.9-Gb/s PDM-OFDM32-QAM and557-Gb/s PDM-OFDM8-QAM signal reveal that the OSNR penalties of the converted idlers are all below1dB, among which the557-Gb/s is the highest data rate in this kind of scheme.Sixthly, to address the issues of inter symbol interference (ISI), inter carrier interference (ICI) and degradation of signal electrical signal-to-noise ratio (ESNR), which is caused by low sibe lobe suppression ratio (SLSR) of conventional OFDM at transmitter in multi-band ultra-large capacity fiber-optic transmsisson systems. A novel digital pulse shaping technology called offset QAM OFDM (OFDM/OQAM) is proposed in this dissertation, which can basically slove the issue of large ISI and ICI. The experimental results indicate that compared with conventional OFDM, the power spectrum density (PSD) of OFDM/OQAM is improved from15dB to35dB and the SNR is also enhanced from17.37dB to18.56dB in multi-band DDO-OFDM system.Moreover, the author of this dissertation together with other team colleagues designed and performed the experiment of C-and L-band DFT-S PDM-OFDM128-QAM modulated100.3-Tb/s (375×267.27-Gb/s) signal transmission over80-km SSMF. This achievement was picked up by academicians of the Chinese Academy of Sciences and Chinese Academy of Engineering as top10China’s news about progress in science and technology in2014(in the8th palce).更多还原