谐波锁模光纤激光器脉冲振幅数值分析

为了研究马赫-曾德尔型调制器的调制特性及锁模脉冲振幅均衡条件,采用调节直流偏置电压和调制深度的方法,来控制调制器透射曲线。通过时域分析,在5GHz调制频率下对锁模脉冲序列和调制曲线进行数值研究。用MATLAB软件模拟分析了2阶～7阶锁模光脉冲序列和调制曲线的时域分布图。数值分析结果表明,锁模脉冲振幅均衡的条件是光脉冲序列经过调制器后经历相同的透射系数。线性调制区与非线性调制区均可获得振幅均衡的锁模脉冲;当有理数谐波锁模阶数p4时,调制深度β变化对脉冲振幅均衡程度影响剧烈。该结果对获得功率均衡的谐波锁模脉冲的实验研究有一定的参考意义。     

脉幅稳定的有理数谐波锁模光纤激光器

通过调节振幅调制器的静态偏压和驱动功率来控制调制器的驱动频率边频分量 ,在 2 5GHz的射频调制频率下 ,有效地抑制了 3～ 5阶有理数谐波锁模脉冲序列的幅度起伏 ,直接由激光器输出幅值稳定的有理数谐波锁模脉冲序列     

基于主动锁模控制的激光谐波研究

介绍一种采用主动锁模控制产生超短激光脉冲序列的方法。首先通过基于主动锁模激光系统的参量自治微分方程思想,导出了系统出现稳定条件时参数设置方法。然后利用铌酸锂的非线性,展开成贝赛尔系数的函数级数,载频与边频数差为调制频率的整数倍,最后产生高重复频率超短光脉冲,得到高阶锁模脉冲,实验结果表明:其通过调节调制器的调制参数来控制谐振腔中的模式损耗,在调制频率为１ＧＨz量级的情况下,可获得重复频率１０ＧＨz的超短光脉冲序列,有啁啾时脉冲时域形状是很好的高斯型,没有出现明显畸变。     

锁模光纤激光器中的矢量孤子簇

为了研究锁模光纤激光器中矢量孤子的动力学特征,利用非线性偏振旋转锁模机制,实验获得了矢量孤子及矢量孤子簇。矢量孤子簇表现出来的动力学特点与抽运功率与偏振设置有关。抽运功率越高,由矢量孤子裂变所形成的矢量孤子簇对数越多。而且,孤子簇脉冲序列在时域上显示出强度周期调制现象。实验中观察到强度周期调制的4阶和7阶脉冲矢量孤子簇。结果表明,强度周期调制的矢量孤子簇输出是非线性偏振旋转锁模光纤激光器偏振调制的本征属性,孤子簇周期强度调制现象归因于腔内偏振相关隔离器对孤子簇的周期偏振调制的结果。     

高次谐波混合锁模脉冲生成及其数值仿真研究

对混合锁模掺铒光纤激光器中高阶谐波锁模脉冲生成进行了试验和仿真研究。利用非线性偏振旋转技术和碳纳米管可饱和吸收体相结合的混合锁模技术，有效降低谐波脉冲锁模泵浦阈值，更加有利于锁模自启动。通过增加泵浦功率，利用峰值功率钳位和孤子能量量化效应，可实现泵浦功率和脉冲重复频率呈线性关系的谐波锁模脉冲输出。当泵浦功率调节为198.8 mW时，激光器最高输出重复频率约为1.31 GHz,约72阶谐波锁模脉冲，其超模抑制比约为35 dB。同时采用基于修正的非线性薛定谔方程进行了数值模拟，通过调节小信号增益系数为3.4和4.4时，单脉冲分裂为等周期间距的2阶和3阶谐波锁模脉冲，数值仿真结果和试验数据基本相吻合。谐波混合锁模脉冲生成的试验和理论结果有利于进一步了解光纤激光器中谐波脉冲的生成原理和方法。     

谐波锁模光电振荡器（特邀）

提出了一种主动锁模光电振荡器（OEO）方案,可以实现高阶谐波锁模,从而产生具有高重复频率的微波脉冲信号。在所提方案中,通过在OEO腔内的电光强度调制器直流偏置端口引入一个正弦驱动信号,当该正弦信号的频率为OEO环腔自由光谱范围的整数倍时,实现基频（）或谐波（）锁模,输出重复频率为的微波脉冲信号。实验中分别实现了10阶、50阶和100阶谐波锁模,输出微波脉冲信号的重复频率分别为360 kHz、1.8 MHz和3.6 MHz。该方案为脉冲多普勒雷达等系统应用提供了一种全新的、具备低相噪潜力的微波脉冲信号产生的技术途径。     

同步泵浦锁模掺铒光纤激光器

通过对泵浦光源半导体激光器(LD)的驱动电源进行正弦调制,实现了掺铒光纤激光器(EDFL)的同步泵浦锁模。在相应于谐波锁模、有理数谐波锁模条件下得到了稳定的脉冲输出。对重复频率544．431。kHz的二次谐波锁模脉冲序列,脉冲宽度为420．4ns,占空比为1．0：4．4,峰值功率为3．34mW;实验中还观察到了自调Q现象,脉冲序列的重复频率为18．25MHz,脉冲半宽度为8ns,占空比为1．0：6．9,峰值功率为2．3mW。     

半导体激光侧面泵浦主动锁模Nd：YAG激光器

报道了用调制频率为４８ＭＨｚ的调幅锁模调制器实现准连续６０Ｗ半导体激光侧面泵浦Ｎｄ：ＹＡＧ激光器的锁模，初模脉冲宽度为１２０ｐｓ。实验中观察到自锁模现象，并对此作了分析。     

可产生高重复频率光脉冲的新理论与新技术

文中论述了获取高重复率光脉冲的一种新方法--有理数谐波锁模技术,阐述了有理数谐波锁模输出高阶光脉冲的物理机制、失谐量与谐波锁模阶数的关系,给出了改善高阶有理数谐波锁模输出脉冲幅度不均衡的几种具体方法.     

主动锁模光纤环形激光器的新进展

在概述主动锁模光纤环形激光器主要特性的基础上,介绍了实现主动锁模的3种技术方案：基于调制器的主动锁模光纤激光器、用半导体激光器作调制器的主动锁模光纤激光器和注入型主动锁模光纤激光器。最后主要讨论了有理数谐波锁模光纤激光器、多波长主动锁模光纤激光器和光子晶体光纤激光器的最新进展,同时指出了当前主动锁模光纤激光器研究的重点。     

Orthonormal pulses for high data rate communications in indoor UWB systems

In this letter, we propose novel pulses which not only meet the power spectral mask of the Federal Communications Commission (FCC) for indoor Ultra-wideband (UWB) systems but also preserve orthogonality at the correlation receiver. The proposed pulses are derived from a parametric closed-form solution. Thus, multiple orthonormal pulses that comply with the FCC mask without additional frequency shifting or bandpass filters can be generated for high data rate communications or multiple access schemes. Simulation results demonstrate that high data rate communication is achieved by the proposed orthonormal pulses via pulse shape modulation and pulse position modulation.     

Performance Evaluation of UWB Systems Exploiting Orthonormal Pulses

The novel pulses, which not only meet the power spectral mask of the Federal Communications Commission (FCC) but also preserve orthonormality at the correlation receiver, have been proposed by Kim for high data rate communications in indoor ultra-wideband (UWB) systems. The proposed multiple orthonormal pulses comply with the FCC spectral mask without additional frequency shifting or bandpass filters, and furthermore, provide enhanced bit-error rate (BER) performance, compared with a well-known Gaussian monocycle and modified Hermite pulses. This paper analyzes the impact of the proposed pulses' properties, such as their auto- and cross-correlations, on the correlation receiver of the UWB system based on the pulse position modulation. The performance of the proposed pulses are compared with different waveforms under various conditions, such as multipath fading, timing mismatch, and multiuser interference. We also discuss a modulation scheme using the multiple orthogonal pulses to achieve the enhancement of data rate and the impact of the correlation characteristics of the proposed waveforms on the BER performance. Simulation results demonstrate the effectiveness of the proposed orthonormal pulses in various conditions, comparing with different waveforms     

半导体激光器的微腔结构调制及其脉码在光纤中的传输

采用腔量子电动力学(QED)方法,定量讨论了平面结构微腔半导体激光器的自发发射特征物理量随腔结构的变化规律.在微腔半导体激光器自发发射因子调制、自发发射寿命调制以及一些实验依据的基础上,提出了微腔结构调制方法.数值模拟了其脉码在光纤中的传输图形.结果表明,微腔结构调制方法在提高脉码比特率方面优于同参数下的电流调制方法.     

利用自相位调制效应测量微结构光纤的非线性系数

报道了利用光纤中的自相位调制(SPM)效应对微结构光纤的非线性系数进行测量的实验.实验中采用半导体激光器作为脉冲光源,输出宽度为1.6 ps的双曲正割型脉冲,经掺铒光纤放大器(EDFA)放大后进入80 m的色散平坦微结构光纤,由于自相位调制效应,出射光谱得到展宽.通过测量输入微结构光纤的脉冲峰值功率和输出光谱,可以计算得到微结构光纤的非线性系数.该测量方法简单、准确,实验测量值与光纤的标称值误差小于1%.     

Modulation instability in erbium-doped fiber amplifiers

The onset of modulation instability in erbium-doped fiber amplifiers (EDFAs) is studied through a stability analysis of the underlying nonlinear Schrodinger equation. The existence of gain in EDFAs lowers the threshold for modulation instability considerably compared with the case of undoped fibers. Modulation instability generates multiple pulses when a single pulse is amplified. It can also create multiple subpulses in mode-locked fiber lasers, a feature observed experimentally. Numerical simulations show that EDFAs can convert a continuous-wave optical signal into a train of high-repetition rate femtosecond pulses     

Improving PPM schemes in wireless infrared links at high bit rates

The authors conclude that pulse-position modulation (PPM) with Gaussian pulses provides better performance than classic PPM schemes with rectangular pulses over unguided optical links operating at high bit rates. In this fashion, both intersymbol interference (ISI), induced by multipath propagation, and the phase distortion effects due to the high-pass filter whose function is to suppress interference, are minimized. However, relevant improvement is not achieved if compared with the OOK format with Gaussian pulses and low duty cycle. The above conclusion is validated by the corresponding bit-error rate (BER) computation using Monte Carlo simulations     

基于正交脉冲波形的高速超宽带通信系统

提出了基于小波函数的两个正交脉冲,其功率谱密度满足美国通信委员会(FCC)对UWB系统的频谱限制。在此基础上提出了使用脉冲波形的极性调制和正交脉冲波形的形状调制相结合的一种高速超宽带通信系统,可以同时传送多个比特信息提高传信率。     

Design of Coding and Modulation for Power-Efficient Use of a Band-Limited Optical Channel

We show thatQ-ary pulse-position modulation with raised cosine pulses minimizes the average power (photons/s) required to communicate at a specified throughput rate (nats/s) over a band-limited, noisy optical channel. The best choice ofQis identified, as are other encoder parameters.     

超辐射掺铒光纤脉冲放大器的时间特性分析

为了分析掺铒光纤脉冲超辐射放大器的输出特性,通过对时变激光速率方程求解的方法,进行了理论分析和数值验证,获得了系统对不同调制频率的响应和输出特性.结果表明,在一定频率范围内,将产生高峰值超辐射脉冲序列.用0.1W抽运1m铒光纤放大,种子具有纳秒级调制周期且占空比为1/2时,输出脉冲峰值渐减,约200ns后渐趋稳定.通过调节种子信号的光谱特性、调制特性并选择合适的光纤参数,可以控制放大脉冲性质.这一结果为利用超辐射光纤光源产生高功率、光谱性质可调的脉冲提供了有效途径,在1.5μm大气窗口及远程应用中具有实际价值.     

1.3μm InGaAsP激光器无偏置增益调制产生ps光脉冲

本文通过求解非线性速率方程分析了半导体激光器增益调制产生ps光脉冲的动力学过程。用自制的双雪崩脉冲发生器产生的短电脉冲无偏置直接驱动InGaAsP激光器获得15ps(FWHM)光脉冲。