Researchon mode division multiplexer with graded-index distribution, low loss and low crosstalk

A graded-index mode division multiplexer with low loss and low crosstalk is proposed. The transmission channel adopts a pure silica core with large effective area to achieve low attenuation, which effectively reduces the splicing loss with pure silica core few-mode transmission fiber. Low differential mode group delay is realized by using graded-index distribution. Also the effective index difference of the modes is greater than 0.5×10-3 to ensure low crosstalk between modes. The performance of the mode division multiplexer is investigated using the beam propagation method and full-vector finite element method. The result shows that the coupling efficiency of multiplexer is better than ?0.479 dB, and the extinction ratio is higher than 31.2 dB in the wavelength of 1 400—1 700 nm. In C band, the average coupling efficiency of all mode channels of multiplexer is better than that of ?0.140 dB, which shows flatness. The proposed scheme is an effective way to implement a multiplexer with low crosstalk, low loss, low fusion loss, high coupling efficiency, high extinction ratio and wide operating band.     

集成运放的前置放大应用

对集成运放的前置放大应用中出现的若干技术问题进行了分析，给出了相应的典型应用实例。     

Sub-picosecond chirped pulse propagation in concave-dispersion-flattened fibers

We propose the sub-picosecond chirped soliton pulse propagation in concave-dispersion-flattened fibers(CDFF).The effects of pulse characteristics and the fiber dispersion parameters on propagation characteristics of the chirped soliton pulse are numerically investigated in the CDFF by the split-step Fourier method(SSFM).The unchirped soliton pulse can stably propagate with unchanged pulse width in the CDFF.The temporal full width at half maximum(FWHM) of the chirped soliton performs a damped oscillation with the increase of propagation distance.The period and amplitude of theoscillation increase with the increase of the chirp parameter |C|.The effect of high-order dispersion(β3-β6) on soliton propagation characteristics can be neglected.The soliton pulse slightly broadens with the increase of propagation distanceand still maintains soliton characteristics when the fiber loss(ATT) is further considered.The variation of root-meansquare(RMS) spectral width with propagation distance is opposite to that of the temporal width.The output spectrum of soliton has a single peak for the unchirped case,while has multi-peak for chirped case.The temporal width of the soliton obviously increases with the increase of the initial width,decreases with the increase of dispersion peak D0 of the fiber,and slightly increases with the decrease of dispersion coefficients k1 and k2 of the fiber.     

MAX7414构成的低通有源滤波器及其应用

分析讨论了一种性能优良的可时钟调谐低通有源滤波器(Butterworth,巴特沃斯型)的有关技术问题,给出了它在电子技术中相应的典型应用实例.它的幅度响应在通带和阻带内呈单调变化,且通带内具有平坦特性,性价比高,具有重要的实用价值.     

柔版印刷金属网栅光电性能研究

为满足日渐增加的电磁屏蔽要求,设计了一种透明基材上柔版印刷电磁屏蔽用金属网栅,研究了影响金属网栅透光率与电磁屏蔽特性的主要因素。首先从理论分析入手,计算并分析金属网栅结构参数（线宽、周期、占空比）等对透明导电金属网栅透光率及电磁屏蔽效能的影响;接下来利用柔版印刷方式制备周期为300、400 ｍ线宽为20、30、40 ｍ的金属网栅,测试了在7、10、13 GHz3个频点处电磁屏蔽效能以及300~1 000 nm波段的紫外-可见透过率。测试与分析结果表明:金属网栅在紫外-可见光波段透过率在70%~80%之间,且随周期/线宽增大而分别增大/减小,电磁屏蔽效能最高达到了15 dB以上。结果显示,网栅的光电特性是矛盾的,线宽与周期越小电磁屏蔽效果越好。     

初始啁啾对凸形色散平坦光纤超连续谱的影响

采用分步傅里叶方法数值研究了线性频率啁啾对高斯光脉冲在凸形色散分布平坦光纤中产生超连续(SC)谱的影响,并与啁啾双曲正割脉冲产生SC谱的情况进行了比较.结果表明:无啁啾高斯光脉冲的SC谱达到200 nm以上,其特性优于双曲正割脉冲的SC谱;获得最佳SC谱所需光纤长度随啁啾参量C增加而缩短;负啁啾时的SC谱特性劣于正啁啾时的特性,2种情况下的SC谱特性均劣于无啁啾时的SC谱特性,SC谱特性的劣化程度随|C|的增加而增大;在最佳SC谱对应的传输距离附近,高斯脉冲频谱质心随C的增加而红移且红移速度逐渐增加,比双曲正割脉冲的红移大且红移速度增加;高斯脉冲方均根频谱和脉宽随传输距离和随C增加逐渐展宽且展宽速度逐渐加快,比双曲正割脉冲的相应参量展宽得快且宽.     

用于波分复用系统的新型掺铒光纤放大器

介绍了可用于波分复用系统的增益平坦、宽带放大的新型掺铒光纤放大器,文中就其结构、性能和实验结果进行了讨论.对实现掺铒光纤放大器的各种不同技术方案进行了分析,提出了适合波分复用系统的掺铒光纤放大器设计思想,为掺铒光纤放大器的深入研究提供了有益参考.     

MAX4310视频复用放大器的应用实例

１ ＭＡＸ４３１０的基本性能ＭＡＸ４３１０是ＭＡＸＩＭ公司生产的单电源工作的低功率高速多路视频复用放大器。它将双通道复用开关和一个可调增益放大器集成在同一芯片上,同时将通道复用开关（低闪变开关）和出色的视频特性结合起来,具备快速通道切换（４０ ｎｓ）、超低切换瞬变１０ ｍＶ（ＰＰ）、－３ ｄＢ带宽２８０ ＭＨｚ、摆率４６０ Ｖ／μｓ与低差分增益／相位误差０．０６％／０．０２°的特性。工作在＋４～＋１０．５ Ｖ的单电源（或双电源±２～±５．２５ Ｖ）,呈现出满电源范围输出和低于地电平的共模输入范围,…     

2.5 Gbit/s光发射模块的中心频率稳定性研究

波分复用的系统光源中心频率的稳定技术是该系统的关键技术之一。本文研究了高速率（以２．５Ｇｈｉｔ／ｓ速率为例）速分复用系统中光发射模块中心频率的稳定技术一温度反馈稳频技术。根据温度反馈稳频技术原理,作者设计并调试了高精度自动控制模块。该控温模块通过控制２．５Ｇｂｉｔ／ｓ光发射模块中激光器管芯温度来稳定其中心频率,为波分复用系统的应用提供了具备稳定中心频率特性的光源。     

初始啁啾对双曲正割光脉冲线性传输特性的影响

采用分步傅里叶方法数值研究了初始线性啁啾和非线性啁啾双曲正割光脉冲在单模光纤反常色散区的线性传输特性，并与啁啾高斯脉冲的线性传输特性作了比较.给出了双曲正割光脉冲频谱宽度和时间带宽积随初始线性啁啾变化的表达式.结果表明，双曲正割脉冲在线性啁啾|C|>0.1时随传输距离的增加逐渐演化成近高斯型，在0≤|C|≤0.1时最后将演化为近双曲正割脉冲.|C|越小，脉冲时域波形越趋近双曲正割曲线.负啁啾对脉冲时域展宽的影响比正啁啾要大得多.当|C|≥0.5时，初始啁啾对双曲正割光脉冲展宽的影响比对高斯脉冲的影响更大.非线性啁啾双曲正割光脉冲在线性传输过程中会出现时域波形分裂现象，比具有相同啁啾的高斯脉冲时域波形分裂严重. 关键词： 频率啁啾 双曲正割光脉冲 线性传输 时域波形分裂