傅立叶域锁模光纤激光器的研究新进展

傅立叶域锁模( FDML)光纤激光器是目前激光领域中比较有活力的研究课题,有着巨大的应用前景.在介绍了FDML光纤激光器的发展状况和应用前景基础,论述了其基本原理,对其关键技术及多种新型技术方案做了介绍和比较,分析FDML光纤激光器的应用前景及发展趋势.     

An optical modulation format generation scheme based on spectral filtering and frequency-to-time mapping

An optical modulation format generation scheme based on spectral filtering and frequency-to-time mapping is experimentally demonstrated. Many modulation formats with continuously adjustable duty radio and bit rate can be formed by changing the dispersion of dispersion element and the bandwidth of shaped spectrum in this scheme. In the experiment, non-return-to-zero (NRZ) signal with bit rate of 29.41 Gbit/s and 1/2 duty ratio return-to-zero (RZ) signal with bit rate of 13.51 Gbit/s are obtained. The maximum bit rate of modulation format signal is also analyzed.     

Multi-pulse operation in an actively Q-switched Er-doped fiber laser based on electro-optic modulator

In this paper, we report an experimental observation of different states of multi-pulse operation in an actively Q-switched Er-doped fiber laser, which has applications in pulse coding in optical communications. The Q factor is switched by an electro-optic modulator. Completely separated multiple pulses are obtained due to the short response time of the modulator. The influence of pump power and modulation frequency on output pulse state is investigated. In the experiment, the repetition rate of Q-switched pulse is not always consistent with the modulation signal. Single-pulse, single-dual-pulse, dual-pulse, dual-triple pulse, and multiple pulses are observed in one modulation period by increasing pump power. Single-pulse is also observed in two or three modulation periods by increasing the frequency of modulation signal. In addition, the waveform of modulating signal and the polarization state of modulated signal also affect the multi-pulse operation accordingly.     

基于掺铒光纤环形滤波器和多模光纤光栅的双波长激光器

提出了基于掺铒光纤环形滤波器和多模光纤光栅的双波长激光器。在单波长光纤激光器的基础上,增加了多模光纤布拉格光栅(MM-FBG)和高精细度的光纤滤波器。其中多模光纤布拉格光栅作为激光器的波长选择元件,可产生两个波长的激光输出。高精细度的光纤滤波器由两个光耦合器和一段弱泵浦的掺铒光纤构成,掺铒光纤产生的增益和光纤时延使滤波器具有高精细度的梳状谱响应,从而抑制了激光器产生的不需要模式,保证了输出的激光具有窄线宽特性。以980 nm的激光二极管(LD)作为泵源,得到了线宽为0.07 nm或0.08 nm的双波长输出,表明滤波器具有良好的滤波效果。     

基于虚拟仪器技术的热处理过程监控系统的设计

本文主要介绍了利用虚拟仪器技术,在图形化编程语言LabVIEW环境下设计出软氮化连续炉监控系统.相对于传统的热处理监控仪表,该监控系统具有参数调节方便、自动化程度高、稳定性好、易实现、成本低等优点.     

Optical arbitrary waveform generation based on an array of tunable apodized waveguide Bragg gratings

A structure of optical arbitrary waveform generation (OAWG) based on an array of tunable apodized waveguide Bragg gratings (WBGs) is proposed. The WBGs array on lithium niobate (LN) consists of several apodized gratings, waveguides and electrodes deposited on both sides of gratings and waveguides. The properties of OAWG are analyzed using transfer matrix method. Due to the electro-optic effect of LN, the amplitude and phase of incident light source are controlled via adjusting the voltages on electrodes. Consequently, the optical pulses with different waveforms are obtained and the amplitude is linearly tuned. In addition, voltages compensating amplitude and phase distortion are demonstrated.     

基于反馈光纤环的可调多波长布里渊掺铒光纤激光器

提出一种基于反馈光纤环(FFL)的多波长布里渊掺铒光纤激光器(MW-BEFL)。主腔由光环形器构成单通谐振腔,长度为50m,而FFL选用传统单纵模布里渊光纤激光器的光纤,长度为10m,以保证每一阶斯托克斯波及反斯托克斯波处于单纵模运行状态,并添加恒温系统消除外界干扰。采用延时干涉法,测得第一阶斯托克斯有45dB的边模抑制比和3.23kHz的线宽,通过调节不同的掺铒光纤放大器(EDFA)功率,对比分析了每一阶斯托克斯波和反斯托克斯波的关系。利用级联受激布里渊散射和四波混频效应,最终获得了50nm(1520~1570nm)可调范围的间隔为0.084nm的15个稳定输出的多波长布里渊掺铒光纤激光器。     

一种自适应模糊控制系统的设计与仿真

模糊控制是在模糊集合理论基础上发展起来的,模糊控制器的设计主要不依靠被控对象的数学模型,但它却非常依靠控制专家或操作人员的经验知识,若缺乏这样的控制经验,很难期望它能获得满意的控制效果.因此,模糊控制器应向着自适应、自组织、自学习发展,使得模糊控制参数或规则在控制过程中自动地调整、修改和完善,从而使系统的控制性能不断改善,达到最佳的控制效果.本文将表格查询学习算法和最近邻聚类学习算法采用加权平均的方法结合起来,确定系统的模糊控制规则,运用基于MATLAB环境下的“模糊推理工具箱”对自适应水位模糊控制系统进行了仿真,取得了很好的控制效果.     

基于LabVIEW技术的虚拟小波消噪仪设计

本文给出了利用虚拟仪器图形化编程软件LabVIEW和数学软件Matlab混合编程设计出虚拟小波消噪仪的方法。文中结合小波变换理论,在LabVIEW中调用Matlab脚本节点,进而对含有白噪声信号进行消噪压缩处理。与传统傅立叶分析消噪相比,该小波消噪仪具有参数调节方便、结果直观、准确及消噪效果好等优点。