亚皮秒级时间分辨率的光取样示波器实验样机

利用自行开发的高稳定、低抖动和重复频率可调的“σ”型被动锁模光纤激光器作为高性能光学取样源,与待测的80 Gb/s光脉冲信号同时输入到100 m高非线性光纤中,通过四波混频效应实现了对被测光信号的全光采样。然后利用自行开发的数字信号处理与计算机图形显示软件,精确地重现了被测试的基于RZ码型的80 Gb/s光脉冲信号波形图。同时,还利用该光学取样示波器实验样机系统对重复频率为10 GHz、脉宽为1.8 ps的商用半导体主动锁模激光器的输出波形进行测量,所显示的脉冲宽度值为2.0 ps。这表明开发出的实验样机系统的时间分辨率优于900 fs。     

Ultrashort optical pulse monitoring using asynchronous optical sampling technique in highly nonlinear fiber

An asynchronous optical sampling scheme based on four-wave mixing （FWM） in highly nonlinear fiber （HNLF） is experimentally demonstrated. Based on this scheme, 10-GHz input pulse train with 1.8-ps pulse width is successfully sampled in 100-m HNLF. A single pulse at 10 GHz with 2.3-ps pulse width is rebuilt by using a 50-MHz frequency tunable free-running fiber laser as the sampling pulse source （SPS）. 40-GHz pulse train is used as the input signal. The rebuilt waveforms, together with the low-jitter eye diagram, are also presented.     

基于半导体光放大器和光滤波器的全光非归零码到归零码的转换

利用半导体光放大器模型和仿真软件对全光非归零码到归零码的变换进行了数值仿真.在仿真结果的基础上,实现了基于半导体光放大器和光滤波器的10 Gbps的全光非归零码到归零码的变换试验.试验结果显示在RZ码输入功率为－15 dBm时,该变换的误码率为1.0×10－9.     

Spatiotemporal evolution of continuous-wave field and dark soliton formation in a microcavity with normal dispersion

Stable dark soliton and dark pulse formation in normally dispersive and red-detuned microcavities are investigated by numerically solving the normalized Lugiato-Lefever equation. The soliton essence is proved by fitting the calculated field intensity profile with the analytical formula of a dark soliton. Meanwhile, we find that a dark soliton can be generated either from the nonlinear evolution of an optical shock wave or narrowing of a locally broad dark pulse with smoother fronts. Explicit analytical expression is obtained to describe the oscillatory fronts of the optical shock wave. Furthermore,from the calculation results, we show that for smaller frequency detunings, e.g., α 3, in addition to the dark soliton formation, a single dark pulse with an oscillatory dip can also arise and propagate stably in the microcavity under proper pump detuning and pump strength combination. The existence region together with various field intensity profiles and the corresponding spectra of single dark pulse are demonstrated.     

一种用于光线性采样的载波相位估计算法

提出了一种改进的相位盲搜索算法,该算法通过两次寻找二次最小欧拉距离得到载波相位噪声的估计值.为验证该算法,搭建了一套光线性采样仿真系统,对符号率为10 Gbaud/s的16QAM光调制信号的星座图进行了测量,采样源为脉宽为500 fs、周期为10 ns的光频梳.仿真结果表明,当两个激光器线宽和小于10MHz时,经过该算法对相位噪声进行补偿后,10G-Gb/s的16QAM信号的星座图能够清晰展示.     

研制超宽带全光取样示波器设备

全光取样示波器是研究与开发超高速光通信系统和光子交换网络的关键性测试仪器设备. 本文简介了我们自行设计和研制出的超宽带全光取样示波器设备的实验样机系统, 并报道了我们已取得的初步实验结果. 采用自主研发的高稳定性被动锁模飞秒光纤激光器作为该光学示波器的光脉冲取样源, 我们通过利用高度非线性光纤中的四波混频效应, 成功地实现了对脉宽为1.8ps、重复频率分别为10GHz和40GHz的光脉冲信号的全光取样. 然后通过数字信号处理和计算机图形处理, 得到了再现后的超短光脉冲信号波形, 并测出了其脉冲宽度值为2.3ps. 借助于该光学取样示波器实验样机, 我们还成功地完成了对脉宽为1.8ps、经过伪随机数据序列调制后的10Gbit/s和40Gbit/s光数据信号眼图的精确测量. 这是我国首次报道有关超宽带全光取样示波器设备的实际研制工作及其相应的实验测试结果. 所得到的有关超短光脉冲信号波形的测试结果也与用70GHz宽带电子示波器和超快光电探测器组成的常规光电测量系统所获得的结果进行了比较, 清楚地表明了我们研制出的全光取样示波器实验样机比后者具有更高的时间分辨率和更大的测量带宽.     

Theoretical analysis of the electromagnetic field inside an anomalous-dispersion microresonator under synthetical pump

We study the spatiotemporal evolution of the electromagnetic field inside a microresonator showing an anomalous dispersion at the pump wavelength by using the normalized Lugiato–Lefever equation. Unlike the traditional single continuous wave(CW) pumping, an additional pump source consisting of periodical pulse train with variable repetition rate is adopted.The influences of the microresonator properties and the pump parameters on the field evolution and the electromagnetic field profile are analyzed. The simulation results indicate that, in the anomalous dispersion regime, both increases of the input pulse amplitude and the repetition frequency can result in the field profiles consisting of multiple peaks. A series of equidistant pulses can also be obtained by increasing the CW pump power. In addition, we find that a large physical detuning between the pump laser carrier and the cavity resonance frequency also causes the splitting of the inside field.     

内置RF电路对增益开关工作的不利影响

对设有内置式RF电路的分布反馈（DFB）半导体激光器在增益开关工作状态下出现反常光谱的原因进行了分析.分别对该激光器在正常工作（即小信号驱动）和增益开关（即大信号驱动）情况下的时域和频域输出结果进行了对比和分析，研究发现内置式RF电路的瞬态失效是导致增益开关DFB激光器产生多波长光谱的原因.     

全保偏双飞秒光纤光频梳系统的频率联动特性

采用跟踪反馈控制法,实现了双飞秒光频梳系统的频率联动,研究了主动光频梳自动扫频和手动扫频情况下,双光梳间的频率联动特性.结果显示,对主动光频梳进行自动扫频或手动扫频时,从动光频梳的频率跟随变化,且双光梳频率间的相关系数最大可达0.99,说明双光梳的频率间保持了较好的联动特性.最后,将频率联动的全保偏双光梳系统用于测距实验中,测量距离为1.332m,时间间隔为0.2s,连续进行16次测量,测得数据的标准差为0.35μm,测量精度可达亚微米量级.     

20-GHz optical pulse source based on cascaded electroabsorption modulators

A high-quality low-timing-jitter 20-GHz optical pulse train is generated by using two cascaded sinusoidally driven electroabsorption modulators(EAMs)at very low bias voltage of-0.8 V in conjunction with a tunable distributed feedback(DFB)semiconductor laser.An approximate transform-limited optical pulse, with the pulse width less than 7 ps,the spectral width of 0.3nm,and the side-mode suppression ratio (SMSR)above 20 dB,is obtained by tuning the optical delay line.