波分复用器在光纤通信中的应用

在光纤通信领域中使用波分复用技术，可以极大地提高网络的传输容量及速率，是解决现代通信技术带宽危机的有效方法．本文介绍了波分复用（WDM）器件的特性，并以双路双向光纤通信为例说明应用WDM技术的优势．     

光通信中的光电子器件讲座第五讲 现代光纤通信中的波分复用技术

波分复用技术在现代光纤通信中发展十分迅速，已展现出巨大的生命力和光明的发展前景。中国的骨士网和一些局域网已开始采用波分复用技术，国内一些厂商也正在开发这项技术。文章详细介绍了波分复用技术的发展背景、原理、组成形式、实现方案及其国内外发展情况。     

可见光通信多维复用技术研究

LED替代白炽灯和日光灯用于照明已经成为明显的趋势。LED可以同时用于照明与通信的特点,使得可见光通信(VLC)成为了近年来国内外研究的热点。由于其具有无辐射、抗电磁干扰、频谱使用无需授权等优势,VLC已成为下一代高速无线接入的新兴技术。目前VLC发展的主要挑战在于LED有限的调制带宽限制了VLC系统的传输速率。针对这一瓶颈,从VLC系统多维复用方式出发,详细介绍了波分复用、频分复用、偏振复用和空分复用四种复用技术,实现多路复用信号并行传输,从而有效提升系统的传输容量。通过对这四种技术原理和性能的分析与讨论,验证了多维复用技术在提升VLC系统传输容量上的可行性,表明了其在VLC系统中广泛的应用前景。     

利用多模干涉效应集成0.98μm/1.55μm波分复用器及掺铒光信号放大器

波分复用器（ＷＤＭ）作为光纤通信中一种重要的元器件，能够在不改变原有通信线路的条件下，有效地增加光纤通信的容量。传统的波分复用器主要基于色散原理，分光比不能准确控制，信号间串音大；而基于平面波导中多模干涉效应研制的波分复用器，具有体积小，损耗低（＜０５ｄＢ），不受光偏振态的影响，易集成等优点；在很宽的工作波长范围内，受环境变化影响小，适合现代通信器件集成化的发展。利用多模干涉效应（ＭＭＩ）集成的０９８μｍ／１５５μｍ波分复用器，波导长度仅几个毫米，分光比例准确，隔离度可达３０－４０ｄＢ，波形失真小，它不仅可用于１５５μｍ光纤激光器和ＥＤＦＡ的集成，也可用于实现１×Ｎ和Ｎ×Ｎ分光，在光纤通信中有广泛的应用前景。     

蚀刻衍射光栅波分复用器件的设计与模拟

近年来光通信飞速发展,波分复用技术(WDM)是满足要求的有效手段.密集波分复用技术已经得到成功商用,其扩展信息传输容量的能力也在不断增强.作为波分复用中最关键的器件,蚀刻衍射光栅(EDG)是平面波导密集波分复用器件中很有发展潜力的一种.本文分析了EDG器件的解复用原理,参量设计,工艺过程.文章最后,建立了一个光栅干涉的简单模型,对设计好的器件参量进行模场形状、谱响应、色散等光栅性能的模拟,得到基本的器件解复用特性,并加以分析.     

聚合物微型谐振环波分复用器

研制出用于现代光通信密集波分复用（DWDM）系统的微型谐振环波分复用器（MRRWM）。微环与信道波导采用垂直耦合的方式,利用耦合模理论对器件参数进行了优化设计,设计出模板,并研制出符合器件光学性能要求的聚合物材料。利用反应离子刻蚀技术完成了硅基板上单级和八级的器件制作,波分复用器的中心波长为1．55μm,输出波长间隔Δλ=1．6nm,中心微环半径R=131．95μm,相邻微环半径差ΔR=500．0nm,器件测试结果表明实现了微环谐振输出。     

基于LED可见光波分复用的音频传输演示仪

利用LED高频率闪烁的响应特性,设计了一种基于LED可见光波分复用的音频传输演示仪。波分复用是让不同波长的可见光同时加载不同信号,通过同一信道传输信息的通信技术。本装置实现了可见光通信技术和波分复用技术的结合,可以大大提高可见光通信的效率。装置亦可用于课堂演示。     

单模光纤窄带波分复用器的研究

由组合波导理论出发，分析了超长耦合器合区光纤间的功率耦合特性以及器件的偏振特性，并提出了研制二段窄波分单模光纤波发复用器的新方法，在研制常规耦合器的工艺基础上，先后研制成功１３１０ｎｍ或１５５０ｎｍ单窗口窄带波分复用器及１３１０ｎｍ或１５５０ｎｍ双窗口等三种复用间隔约１４ｎｍ的窄带波分复用器，其波长隔离度大于２０ｄＢ，具有２～３ｎｍ的带宽，偏振灵敏度小于０．１ｄＢ，附加损耗小于０．５ｄＢ，这些参数     

光纤马赫—陈德尔干涉型8波分超窄波分复用器的研制

报道了采用７个单模光纤马赫－陈德尔干涉仪进行三级串联而组成的８波分复用器，既保留了干涉型光纤波分复用器超窄波分复用间隔的优点，又消除了其复用路数少的缺点。文中介绍了这类波分复用器的原理、设计方法和制造技术。实验样品的使用波段为１．５μｍ，波长复用间隔为２．４ｎｍ，整个器件的附加损耗约为１．５ｄＢ。     

短程透镜-光栅型集成波分复用器

制备了一种短程透镜——光栅型集成光学波分复用器。本文简述了波分复用器的原理和制备工艺,描述了其中的关键元件光波导光栅和光波导透镜的设计及特性测量,给出了波分特性的实验结果.     

Tbit/s超大容量光纤通信系统的研究进展

Tbit/s超大容量光纤传输系统促进了光纤通信技术的发展。综述了采用波分复用技术(WDM)、光时分复用技术(OTDM)和WDM/OTDM混合方式的Tbit/s超大容量光传输系统的研究现状、技术实现方式及研究的最新进展。对各种传输系统的优缺点进行了评价,对Tbit/s光纤通信系统的前景作了展望。     

Ultrafast and Wideband All-Optical Processing Technologies Towards Flexible Photonic Networks

Recent progress in ultrafast and wideband all-optical processing technologies to realize flexible and transparent optical time-division multiplexing (OTDM)/wavelength-division multiplexing (WDM) photonic networks is reviewed covering ultrafast OTDM technologies handling more than 100 Gbit/s per wavelength channel and wideband WDM technologies handling more than 1000 wavelength channels over the 200 nm range.     

Impact of a Post-OTDM-Demultiplexing Optical Filter on Dense OOK OTDM-WDM Transmission

The impact of a post-OTDM-demultiplexing optical filter on the performance of dense on-off keying (OOK) optical time division multiplexing (OTDM)—wavelength division multiplexing (WDM) systems was studied. For return-to-zero (RZ) modulation, it was found that the additional filter working in a double-tier filter configuration did not offer any significant improvements to performance when the signal pulse width is optimized. Improvements generally increase only when the signal pulse width deviates from its optimal value and only for low spectral densities. For ideal non-return-to-zero (NRZ) modulation, however, significant improvements of around 1 dB are obtained using the double-tier configuration over a large range of spectral densities.     

Characterization of wavelength interleaving in radio-over-fiber systems employing WDM/SCM

A radio-over-fiber (RoF) distribution system incorporating both sub-carrier multiplexing and wavelength division multiplexing (WDM) technologies is presented. This signal is directly modulated onto three high-speed lasers. Bragg filters are employed at the receiver base station in order to both demultiplex the required optical channel, and ensure that the detected signal is single side band (in order to overcome dispersion limitations of the link). System spectral efficiency is optimised by wavelength interleaving. The channel spacing between the WDM channels is varied and the system performance for different values of channel spacing and spectral efficiencies is investigated. The results show that wavelength interleaving is a reliable technique that could be used to increase the spectral efficiency of RoF systems.     

Absolute polar duty cycle division multiplexing over wavelength division multiplexing system

The performance of absolute polar duty cycle division multiplexing (AP-DCDM) over wavelength division multiplexing (WDM) system is presented based on the simulation results. The AP-DCDM signal has narrower bandwidth than conventional time division multiplexing (TDM) signal, which makes its implementation in WDM system advantageous. In this paper, characteristics of AP-DCDM and TDM signals in WDM system are compared at the speed of 40 Gbit/s per channel, for the minimum allowed channel spacing and the chromatic dispersion tolerance. The results clearly show that AP-DCDM performs significantly better than TDM. By using AP-DCDM, 1.28 Tbit/s (32 × 40 Gbit/s) was successfully transmitted over 320 km standard single mode fiber. Spectral efficiency of 0.64 b/s/Hz was achieved by using 10 Gbit/s transmitters and receivers without polarization multiplexing.     

面向LOFAR应用的160Gbit/s OTDM 试验平台

报告了一个用于低频射频天线网络LOFAR的160 Gbit/s 演示平台.文章介绍了LOFAR网络结构以及用于LOFAR长臂的OTDM/WDM系统结构，回顾并探讨了用于实现160 Gbit/s系统的关键技术，并介绍了实验室中实现该160 Gbit/s OTDM/WDM演示平台所采用的技术方案。出于经济性考虑，所有的关键系统功能都采用自己搭建方案.     

Analysis of physical layer performance of hybrid optical-wireless access network

The hybrid optical-wireless access network (HOWAN) is a favorable architecture for next generation access network. It is an optimal combination of an optical backhaul and a wireless front-end for an efficient access network. In this paper, the HOWAN architecture is designed based on a wavelengths division multiplexing/time division multiplexing passive optical network (WDM/TDM PON) at the optical backhaul and a wireless fidelity (WiFi) technology at the wireless front-end. The HOWAN is proposed that can provide blanket coverage of broadband and flexible connection for end-users. Most of the existing works, based on performance evaluation are concerned on network layer aspects. This paper reports physical layer performance in terms of the bit error rate (BER), eye diagram, and signal-to-noise ratio (SNR) of the communication system. It accommodates 8 wavelength channels with 32 optical network unit/wireless access points (ONU/APs). It is demonstrated that downstream and upstream of 2 Gb/s can be achieved by optical backhaul for each wavelength channel along optical fiber length of 20 km and a data rate of 54 Mb/s per ONU/AP along a 50 m outdoor wireless link.     

Effects of pulse chirp on supercontinuum produced in dispersion decreasing fibre

The supercontinuum (SC) source plays a key role in wavelength division multiplexing over the optical time division multiplexing (WDM/OTDM) transmission system. The SC produced in dispersion decreasing fibre (DDF) is wider and flatter than that produced in dispersion shifted fibre (DSF). In this paper, a SC producing process in DDF is numerically simulated, the effects of pump pulse chirp on the SC width and flatness are initially studied and the corresponding theoretical explanations are given. Particularly, we have analysed and compared the evolutions of the SC along DDF pumped by different chirp pulses. Several valuable conclusions are obtained.