ROF系统中基于四波混频的全光波长变换的研究

理论分析了基于四波混频(FWM)实现ROF(光载射频系统)全光波长变换.在分析基于高非线性光纤中FWM效应实现全光波长转换的基础上,指出影响转换效率的主要因素,讨论了提高转换效率的几种方法,采用提高非线性系数、光纤长度、调整泵浦光的功率以及信号光和泵浦光偏振方向之间的关系可以有效地提高基于FWM的波长变换效率,从而为在ROF系统中高效实现波长变换技术提供了依据.同时通过仿真实验,验证了已有的理论分析.     

基于非线性光纤环镜的全光波长变换器性能分析

非线性光纤环镜是一种很有前途的全光波长变换装置。介绍了利用光束传输法（ＢＰＭ） 对耦合非线性薛定谔方程组进行数值解析,详细讨论了对变换信号质量起作用的因素,包括泵浦光脉冲与信号光脉冲之间的走离和初始时延、光纤长度、向长波长变换和向短波长变换等。结果表明,适当的初始时延可以补偿走离的影响,适当增加光纤长度可以改善脉冲波形。     

脉冲泵浦双包层掺Yb3+光纤放大器理论研究

对比研究了在连续泵浦和脉冲泵浦两种情况下,高功率双包层掺Yb3+件光纤放大器的输出特性.计算结果表明:采用脉冲泵浦放大50 kHz高斯脉冲信号,在ASE光抑制方面和光纤放大器热效应方面都优于连续泵浦情况下的光纤放大器.进一步又研究了脉冲泵浦下,从泵浦脉冲峰值功率,掺杂光纤浓度和泵浦波长三方面选择泵浦脉冲宽度,优化放大器输出特性.为提高和设计掺Yb3+抖光纤放大器和MOPA系统的输出功率和稳定性提供了理论依据.     

增益分布对皮秒脉冲自相似放大的影响

采用数值模拟的方法,研究了增益分布对皮秒脉冲自相似放大的影响。构建了掺镱光纤内超短激光脉冲自相似放大的理论模型,以不同的泵浦方式、光纤长度和总增益系数实现不同的增益分布,探究了不同增益分布对增益光纤中皮秒脉冲的自相似放大过程和结果的影响。结果表明,皮秒脉冲在不同的增益分布下存在最佳的自相似放大结果,可以得到近变换极限的百飞秒高质量脉冲输出。发现同一信号光脉冲在增益光纤中演化至自相似放大过程时,正向泵浦方式下的演化速度比反向泵浦快。对于不同的增益光纤长度和总增益系数,正向泵浦方式下的信号光自相似区域主要集中在低入射脉冲能量和长波长区域,反向泵浦方式下的信号光自相似区域主要集中在高入射脉冲能量和短波长区域。     

2.8 μm中红外同步泵浦锁模光纤激光器

2.8μm波段中红外光纤激光器在激光医疗领域具有重要的应用,受到广泛关注。研究并实现了2.8μm同步泵浦锁模脉冲光纤激光器。自主研制了大功率单模976nm皮秒脉冲激光器并以此作为泵浦源,以掺铒氟化物光纤环形腔作为谐振器,通过纤芯同步泵浦的方式,在交叉相位调制作用下实现了2.8μm同步泵浦锁模脉冲激光器的制备。锁模脉冲的中心波长为2784.7nm,重复频率为6.534 MHz,脉冲宽度接近光电探测器极限。所提方案不需要在谐振器内插入任何中红外主动或被动调制器,具有系统稳定性好和易于实现全光纤化等优势。     

光纤中基于交叉相位调制与喇曼放大的超短光脉冲串的产生

本文提出一种在单模光纤负群速色散区连续波产生超短光脉冲串的新方法，即让波长位于光纤负色散区的连续波和波长位于光纤正色散工铁泵浦脉冲串在光纤中共同传输，在光纤的零色散波位于连续波长与泵浦脉冲波长中间附近的情况下，交叉相位调制与喇曼放大能使连续波演化成比泵浦脉冲窄得多的无调啾，无脉座的超短光脉冲串。数值计算表明，泵浦脉冲愈强，由连续波产生的超短光脉冲宽度愈宽，峰值功率愈高，而且所需的光纤愈短。     

光子晶体光纤中双脉冲非线性传输的数值分析

采用分布傅立叶方法数值求解耦合的非线性薛定谔方程,模拟了双脉冲在光子晶体光纤中的非线性传输过程,计算和分析了离散效应和脉冲内拉曼散射对信号脉冲传输和压缩的影响。结果表明,当中心波长为800nm的泵浦脉冲在反常色散区进行泵浦,而中心波长为740nm的信号脉冲在正常色散区入射,在群速度色散,自相位调制及交叉相位调制联合作用下,信号脉冲在传输过程中不仅被压缩且存在最佳光纤长度。离散效应不仅导致脉冲压缩比的减小和压缩后峰值功率的降低,而且导致脉冲所需最佳光纤长度的增加以及压缩后的脉冲呈现不对称,还发现,脉冲内拉曼散射有利于改善脉冲压缩质量。     

侧面分布式泵浦双包层脉冲光纤放大器

采用自行研制的光纤侧面耦合器,设计和研制了侧面分布式泵浦、两级全光纤连接的掺镱双包层脉冲光纤放大器,实现了输出波长为1064nm、平均输出功率达到2.12W、脉冲宽度20ns、重复频率50kHz的高功率、高重复频率全光纤结构脉冲光纤放大器.光纤侧面耦合器对泵浦光耦合效率最高达到69%,对反向信号光的隔离度最低为17dB,有效避免了高功率脉冲回波对泵浦光源的损害,使用更高泵浦耦合效率的侧面耦合器,可进一步提高放大器输出功率.     

基于高非线性光纤和SOA非线性效应的星上再生波长变换

针对分布式卫星系统信息交换频繁、波长变换频 次高且由此导致信号损伤严重的特点, 提出了一种基于高非线性光纤(HNLF)和半导体光放大器(SOA)非线性效应的星上全光再生 波长变换方案。利用HNLF的自相位调制(SPM)效应对原始信号频谱进行展宽,通过 红移或蓝移滤波取出预变换信号,分别作为波长上变换或下变换的泵浦光信号,最后基于 SOA的四波混频(FWM)效应实现了对原始信号的波长变换。理论推导了波长变换方案的工 作原理,分析了波长变换性能与各结构参数之间的关系。仿真实验结果表明:本文方案在有 效 实现波长变换的同时能够一定程度地改善信号质量,Q因子改善 最高可达3dB以上,功率转换效率可达到20dB。     

泵浦波长对光子晶体光纤中飞秒脉冲压缩的影响

采用分布傅立叶方法数值模拟了飞秒光脉冲在光子晶体光纤反常色散区的非线性传输和压缩过程。计算和分析了不同泵浦波长对光子晶体光纤中超短脉冲传输和压缩的影响,结果表明,在相同初始脉冲峰值功率条件下,泵浦波长为1000nm的脉冲压缩因子和峰值功率最大,最佳光纤长度最短,但品质因子适中,并且随着初始峰值的增大,其压缩因子增长幅度最大。合理选择泵浦波长,有利于增强压缩效果,提高脉冲压缩质量和峰值功率,使得最佳光纤长度减小。     

基于非线性光纤环形镜的二光平信号全光分离器

非线性光纤环形镜(NOLM)在不同抽运条件下具有不同的连续波开关特性,当单抽运NOLM在抽运峰值功率大于开关阈值功率时具有反转抽运脉冲峰的特点,在抽运脉冲上升与下降沿处各产生一个脉冲输出;当使用双脉冲抽运在两抽运脉冲除峰值功率和波长不同外其他参数一致时,透射输出由两个脉冲的峰值功率差决定,具有脉冲峰值功率比较作用。基于NOLM的这两个特性设计了全光分离两光功率水平信号的方案。利用光子学仿真软件进行了数值仿真,结果显示二光平信号被成功分离,并分别加载到不同波长上。实现了高功率级无基座脉冲输出,表明该方案也具有消除脉冲基座的能力。     

Generation of bright and dark soliton trains from continuous-wavelight using cross-phase modulation in a nonlinear-optical loop mirror

A simple technique for the simultaneous generation of bright and dark soliton trains from continuous-wave (CW) light is proposed and demonstrated theoretically. It is based on the optical switching characteristics of a nonlinear-optical loop mirror (NOLM) through which the CW signal is switched by a pump pulse train at another wavelength by the creation of cross-phase modulation-induced phase bias between the counter-propagating CW components. The transmitted and reflected signals exiting from the NOLM can then evolve, respectively, into bright and dark soliton trains in fibers with the appropriate group-velocity dispersion at the signal wavelength. Numerical simulations indicate that the generated solitons can be narrower than the pump pulses and that the scheme permits the conversion of nearly all of the CW energy into the soliton train energy without generating pulse pedestals     

Simultaneous 4 × 10 Gb/s NRZ-to-RZ Modulation Format Conversion in Nonlinear Optical Loop Mirror With a Photonic Crystal Fiber

Orthogonal cross-phase-modulation (XPM) scheme in a nonlinear optical loop mirror (NOLM) is proposed to simultaneously convert four synchronized 10-Gb/s nonreturn-to-zero signals into return-to-zero (RZ) format. Modulation format conversion is achieved by using a synchronized optical control pulse train as the pulse carver in a NOLM. The control pulse train and the targeted signals are orthogonal in their states of polarization. This orthogonal nonlinear interaction substantially suppresses the undesirable four-wave mixing (FWM) induced crosstalk in the multichannel operation. Experimental demonstration of the proposed scheme shows that the suppression of the generated FWM idler is >26 dB. Error-free operation is achieved for the four converted 10-Gb/s RZ signals in a single NOLM by sharing the nonlinear XPM effect induced by the control pulse train.     

长腔被动锁模掺镱光纤激光器的方波脉冲产生

报道了一种基于非线性光纤环形镜(NOLM)、工作在耗散孤子共振(DSR)区的长腔被动锁模掺镱光纤激光器,该激光器谐振腔的总长度约为1502 m,可以输出重复频率为133.18 kHz的高能量方波脉冲,且输出脉冲的宽度和单脉冲能量均随泵浦功率的增大而呈线性增大。当泵浦功率增大到414.47 mW时,输出的方波脉冲具有最大宽度(761.6 ns),同时单脉冲能量达到了最大值(60.2 nJ)。通过改变NOLM中单模光纤的长度,进一步研究了谐振腔长度对输出方波脉冲特性的影响,结果表明:谐振腔越长,所得DSR方波脉冲越宽,脉冲峰值功率越低。     

哑铃形高功率全保偏大模场掺镱锁模光纤激光器

采用基于非线性光纤环形镜的哑铃形结构搭建了全光纤全保偏掺镱锁模激光器。通过使用全保偏大模场光纤、高功率光纤器件和优化的腔结构,实现了脉冲宽度在156 ps到8.1 ns范围内可调的高功率、大能量矩形耗散孤子共振脉冲输出,在最大泵浦功率22.7 W下激光器直接输出功率达到5.5 W,脉冲能量达到0.68μJ,峰值功率为84 W。得益于全保偏光纤结构,所设计的激光器具有出色的抗干扰性和稳定性。     

All-optical wavelength conversion of short pulses and NRZ signalsbased on a nonlinear optical loop mirror

Wavelength conversion of short pulses at 10 GHz based on a nonlinear optical loop mirror (NOLM) is experimentally and numerically investigated for the case of small group velocity dispersion and walkoff between the control pulses and continuous lightwaves. Experimental and numerical simulation results show that the pulsewidths of the converted signals at different wavelengths are almost the same, and the pulsewidths are compressed when the peak power of the control pulse is smaller than a certain value. An RZ optical source containing eight wavelengths having a high sidemode suppression ratio, equal amplitudes and almost the same pulsewidths is obtained by using wavelength conversion in a NOLM consisting of a common dispersion shifted fiber. 10 Gb/s NRZ wavelength conversion based on the NOLM is demonstrated for the first time and certain conclusions in some of the references are confirmed by our experimental results     

NOLM中反向交叉相位调制作用分析

提出了反向交叉相位调制(XPM)耦合方程,得出了非线性光学环路镜(NOLM)中正、反向信号脉冲在传输过程中共同作用的非线性相移,研究了高斯脉冲情况下NOLM的开关特性,NOLM作为解复用器时反向XPM的影响,及作为光路由选择单元时无放大联接的级数.最后讨论NRZ码情况下的开关特性.     

Generation of a 4 /spl times/ 100 GHz pulse-train from a single-wavelength 10-GHz mode-locked laser using superimposed fiber Bragg gratings and nonlinear conversion

In this paper, the design of a simple and practical repetition-rate multiplier based on superimposed-chirped fiber Bragg gratings (FBGs) is presented. A tenfold increase in the repetition rate of a mode-locked fiber source, by generating a 100-GHz optical pulse train from a 10-GHz train, is demonstrated experimentally. As compared with previous demonstrations, the superimposed FBG filter was specifically designed to decrease the duty cycle of the generated pulse train or, in other words, decrease the pulsewidth. In addition, a fiber nonlinear optical loop mirror (NOLM) is used to eliminate the pulse-to-pulse phase fluctuations in the output high-repetition-rate train and to achieve a wavelength-tunable transform-limited pulse sequence. Moreover, it is shown that nonlinear conversion using the NOLM can be used to simultaneously generate multiwavelength high-repetition-rate optical pulse trains (4 /spl times/ 100 GHz in the example shown here).     

变占空比脉冲测量非线性光环镜阈值特性的实验研究

光阈值器件是多用户光码分多址(OCDMA)系统接收机中抑制基底噪声和互相关旁瓣峰的重要部件。非线性光环镜(NOLM)是实现光阈值的一种有效方法。对基于高非线性光纤(HNLF)NOLM的阈值特性进行了实验研究及数据分析,提出利用改变抽运脉冲占空比分析阈值特性的方法,实验发现抽运脉冲占空比D为1/25时出现阈值点,阈值功率为3.75W。讨论了抽运光与信号光的波长间隔对NOLM输出信号的影响,得出阈值点处的最优波长间隔为5.8nm,脉冲压缩量为114.47ps。实验搭建了接收机阈值系统,眼图分析表明该系统能较好地抑制噪声。     

All-optical TDM data demultiplexing at 80 Gb/s with significant timing jitter tolerance using a fiber Bragg grating based rectangular pulse switching technology

We demonstrate the use of fiber Bragg grating based pulse-shaping technology to provide timing jitter tolerant data demultiplexing in an 80 Gb/s all-optical time division multiplexing (OTDM) system. Error-free demultiplexing operation is achieved with /spl sim/6 ps timing jitter tolerance using superstructured fiber Bragg grating based 1.7 ps soliton to 10 ps rectangular pulse conversion at the switching pulse input to a nonlinear optical loop mirror (NOLM) demultiplexer comprising highly nonlinear dispersion shifted fiber (HNLF). A 2-dB power-penalty improvement is obtained compared to demultiplexing without the pulse-shaping grating.