【作者】 嵇誉；

【导师】 林金桐；

【作者基本信息】 北京邮电大学 ， 通信与信息系统， 2013， 博士

【摘要】 随着各种高带宽高速率需求业务的不断涌现,如4G高速移动通信业务,高清视频、实时游戏、远程医疗、视频会议、电子商务、物联网等,对光纤通信系统的带宽和容量提出了更高的需求。提高光通信系统传输容量的方法主要有：提高单波道的速率,增加更多的波长数目,提高频谱效率等。这些方法可以通过光时分复用(OTDM)技术、波分复用(WDM)技术、光正交频分(OFDM)技术、高阶调制格式等方案来实现。本论文的研究内容主要集中在OTDM系统中超短脉冲光源产生技术和解复用技术,160GBaud差分正交移相键控(DQPSK) OTDM信号传输,频率梳的产生以及基于频率梳产生高速信号等方面。主要成果和创新点包括以下几个方面：1、论文中建立了简单有效的电吸收调制器(EAM)行波电极模型,实验验证了单个EAM和级联EAM产生脉冲的方案。单个EAM可以得到5ps的脉冲,级联EAM产生的脉冲更窄但是信噪比(SNR)恶化。为了得到高质量的窄脉冲,提出了三种超短脉冲光源产生方案。首先,对利用铌酸锂强度调制器级联两个相位调制器产生超短脉冲的方案进行了理论分析和实验验证。在此基础上提出了利用EAM级联两个相位调制器,和利用双平行调制器(DPMZM)级联两个相位调制器产生超短脉冲的方案。上述三种方案均可产生重复频率为40GHz,半高全宽(FWHM)约为2ps,时间抖动低于100fs,消光比(ER)大于20dB,信噪比高于25dB的超短脉冲。通过DQPSK信号背靠背调制、解调,实验验证了其相位稳定性。对这三种方案进行比较和分析得到,基于铌酸锂马赫-曾德尔调制器(MZM)的方案产生的脉冲基座较大,消光比(ER)低,但损耗小：基于EAM方案差损较大、信噪比低但消光比高；双平行调制器方案较好,信噪比和消光比都很高,但是必须有偏压控制才能保证其长期稳定工作。2、论文提出了分别利用EAM、DPMZM、偏振调制器将160GBaud的DQPSK信号解复用到40GBaud的方案。首先通过利用自级联EAM产生2.7ps的窗口,将160GBaud DQPSK信号解复用到40GBaud,4路复用/解复用的功率代价均低于2dB。其次,详细分析了DPMZM产生窗口的特性,并将产生的5.7ps的窗口利用到160GBaud DQPSK系统中,实现了支路信号的零误码解复用,功率代价仅为0.2dB。然后,提出了利用偏振调制器将160GBaud DQPSK信号解复用到40GBaud的方案,实验得到解复用的窗口宽度为5.4ps,ER大于15dB,SNR超过28dB。解复用带来的功率代价小于1.8dB。最后分析了上述三种方案的优劣。3、将超短脉冲光源和解复用模块应用到高速传输系统中,研究了信号传输的性能。完成了40GBaud信号到160GBaud的光复用器的制作和400km G.657光纤传输链路的设计。系统采用DQPSK调制格式,支路速率为40GBaud,总传输速率达到320Gb/s,经过400km传输后,I路灵敏度代价在2.5dB左右,Q路灵敏度代价在3dB左右。提出了一种脉宽可变的载波抑制归零码(CSRZ)信号的产生技术,并研究了不同宽度的CSRZ-DQPSK传输性能。利用一个DPMZM产生了40GHz脉冲宽度分别为7.8ps、12ps、15.5ps的信号,将其调制、传输320km后得到零误码。发现当脉冲宽度为12ps时,产生的CSRZ-DQPSK信号传输性能最好,I路和Q路灵敏度功率代价分别为2.6dB和2.7dB。4、提出了级联DPMZM产生平坦频率梳和基于频率梳产生高速信号的方案。研究了利用级联DPMZM产生25根谱线,幅度变化低于0.75dB,边摸抑制比约为20dB的超平坦频率梳,其频率间隔和波长均可灵活改变。在产生稳定的频率梳基础上研究利用可编程光学处理器产生高质量的毫米波和太赫兹波。可获得范围从40GHz到440GHz变化的信号,并分析了产生的毫米波和太赫兹波信号的频谱特性。同样利用可编程光学处理器对频率梳进行处理,产生了2～8倍40GHz脉冲信号而且脉冲宽度维持在1.9ps,信噪比超过26dB。最后提出了利用一个DPMZM被40GHz的正弦信号驱动产生了160GHz的脉冲信号的方案,并进行了仿真分析和实验验证。产生的160GHz脉冲FWHM为3.3ps,SNR为28.5dB。更多还原

【Abstract】 With the quick development of high speed and larger capacity busesiness, such as4G mobile communication, high-definition video, real-time games, telemedicine, Internet of Things, and so on, they propose great demand for high-speed backbone network. There are several ways to increase the capacity of optical communication system, such as:to increase the single-channel rate, add more wavelengths, improve the spectrum efficiency, and manufacture new types of fiber etc. These methods can be achieved through optical time optical time division multiplexing(OTDM), wavelength division multiplexing(WDM), orthogonal frequency division multiplexing and using high order modulation format. The content of this thesis is mainly focused on the high speed ultra-short optical pulse generation; demultiplexion technique;160GBaud differential quadrature phase shift keying (DQPSK) OTDM signal transmission; the generation of frequency comb and high speed signals.The main achievements and innovations are summarized as follows:1. A traveling wave electrode model of electro-absorption modulator (EAM) is proposed. Then, pulse generation based on a single EAM or cascaded EAMs are experimentally demonstrated. It is found that pulses with full width at half maximum (FWHM) of5ps can be generated using one EAM while3ps can be achived through cascaded EAMs, but the signal-noise ratio (SNR) is degraded seriously. To this end, three different generation methods are proposed to obtain short pulses with high quality. Firstly, based on the modulation function of the lithium niobate modulator, Mach-Zehnder modulator(MZM) and two phase modulators (PM) are used to generate ultra-short pulses. On this basis, using an EAM or a dual parallel MZM (DPMZM) cascaded with two PMs to generate ultra-short pulses is proposed and experimentally demonstrated. The generated40GHz ultra-short pulses are all with FWHM of～2ps, time jitter less than100fs, the extinction ratio (ER) larger than20dB and SNR larger than25dB. The phase stability is verified through DQPSK modulation and demodulation. At last, the advantanges and disavantages of the proposed methods are analyzed.2.160GBaud DQPSK signal to40GBaud de-multiplexing using EAM or DPMZM or polarization modulator are proposed and experimentally demonstrated. Firstly,2.7ps optical window is generated through self-cascaded EAM, and then it is used in160GBaud DQPSK signal to40GBaud de-multiplexing system. The measured demultiplexing power penalty is less than2dB. Second, the characteristics of the optical switch generated from the DPMZM are analyzed in detail. Then, the generated5.7ps window is used in160GBaud DQPSK system, and error free performance is achieved with only0.2dB power penalty. Thirdly, a polarization modulator is used to generate the optical switch with FWHM of5.4ps, ER larger than15dB and SNR exceeds28dB. The demultiplexing power penalty is less than1.8dB. The three approaches have their own strengths and weaknesses, which lead to different application scenarios.3. We have built up the high speed transmission platform and investigate the different signals transmission performance.The generated40GHz ultra-short pulse after DQPSK modulation is multiplexed to160GBaud and error free performance is achieved after410km G.657fiber transmission. Then, DPMZMs are used to generate pulse width tunable CSRZ-DQPSK signals. Error free performance is achieved after320km transmission for different width puses.The results show that12ps signal achieves the best performace.4. Ultra-flat phase and frequency locked frequency comb is generated using two cascaded DPMZMs. Based on frequency comb and programmable optical processor, high frequency-purity and low phase noise millimeter wave or terahertz wave signals with frequency from40GHz to as high as440GHz are successfully generated. Also,2,3,4,5,6,7,8times of the40GHz pulses are generated based on programmable optical processor and frequency comb.The generated pulses are with almost the constant pulse width of1.9ps, good ER and improved SNR over26dB.Finally,160GHz50%CSRZ signal generation only using a DPMZM driven by a40GHz sinusoidal signal is proposed and experimentally demonstrated.更多还原