WDM光网中虚拓扑重构的优化设计

采用优化方法来研究光网络业务发生改变时的虚拓扑重构问题,并提出了相应的混合整数线性规划算法.主要的思路是当业务发生改变时,寻找既能保证网络性能又对现有业务中断最小的虚拓扑.对影响虚拓扑重构的因素进行了研究,发现,如果使网络性能达到次优而不是最优可以大大减少对现有业务的中断.     

A Pixelized Variable Optical Attenuator Using Liquid Crystal on Silicon Technology for Tunable Filters

We apply liquid crystal on silicon (LCOS) in 0.8-$mUm standard complementary metal-oxide semiconductor (CMOS) technology to demonstrate a low-cost, high-performance pixelized liquid crystal variable optical attenuator (VOA) with pulse width modulation. We then build a prototype tunable filter by using this VOA along with a grating in the Littrow configuration. With the application of 5-V pulse width modulation, the proposed VOA achieves a 5.6-dB insertion loss, a dynamic range of more than 20 dB, a 50-GHz channel spacing capability, and a polarization-dependent loss (PDL) of less than 0.6 dB at 15-dB attenuation. Our VOA is suitable for applications such as dynamic channel gain equalizers, channel-blocking filters, sub-components of re-configurable add-drop modules, and wavelength selectors.     

Fast intra-modal and inter-modal wavelength switching of a high-speed SG-DBR laser for dynamic wavelength routing

As the SG-DBR laser is among the most attractive sources for WDM and DWDM systems, it is important and necessary to investigate its wavelength switching characteristics. This behaviour will affect wavelength routing and the capability limits for channel re-allocation in future optical networks. This paper presents detailed experimental studies on a high-speed SG-DBR laser by using a Fabry–Perot Interferometer technique adapted for the non-continuous wave case. Measurements of fast intra-modal (i.e. cavity mode) and inter-modal (i.e. super-mode) wavelength switching and insights into the device's dynamic behaviour are obtained. Implications are given for transmitter design in dynamic wavelength routing and channel re-allocation.     

单纤双向WDM滤光片的研制

随着光纤接入网的发展 ,对光纤器件的价格、性能等方面提出了更严格的要求。尤其是当光纤线路紧张时 ,需要进行单纤双向传输。滤光片是关键元件 ,它分别要求 1310nm透过时要大于 98%、15 5 0nm反射时要大于 95 %以上 ,或者 1310nm反射时大于 95 %、15 5 0nm透过时大于 98%以上 ,并且带宽为± 40nm。由于滤光片尺寸较小 ,必须切割划片 ,所以对膜层的牢固度有很高的要求。经过膜系优化和大量的工艺实验 ,提供的样品完全满足用户的要求 ,现已定型批量生产。     

WDM光网络串扰特性分析与实验研究

提出了WDM光网络系统串扰分析统一的数学模型,分析比较了WDM光网络系统各种串扰的起源与特征,实验研究了不同的非相干串扰代价下,WDM光网络系统的功率代价.对应1dB功率代价下,得出WDM光网络系统对应非相干串扰代价容限小于-20dB的结果.     

WDM网中同频串扰的研究

串扰是波分复用(WDM)光网络中限制光交叉连接(OXC)节点容量的一个重要因素.本文分析了相干和非相干串扰对通过OXC节点的光信号的影响,给出了固定和最佳判决门限两种情况下的光功率恶化,并进行了仿真计算.结果表明相干串扰对系统的影响很大.与固定判决相比,采用最佳判决可以降低串扰影响.串扰引起的光功率恶化主要取决于复用波数M,而与输入光纤数N关系不大.为了减小串扰对网络的限制,可以在OXC节点内使用滤波器.     

A Novel Add/Drop Multiplexer Architecture for DWDM Network

By using the coupled-mode theory and F-matrix method, the transmission spectra of apodized phase-shifted LPFGs are calculated and analyzed. A novel configuration of OADM is proposed for flexible multiple wavelengths add-drop based on cascaded phase-shifted LPFGs filters with apodization technique.     

RWA scheme minimizing FWM effect in a wide area optical network

In WDM based fiber optic communication systems, nonlinearities deteriorate network performance. A channel wavelength assignment scheme is required which not only minimize the FWM effect but also the network delay produced during assignment process. Wavelength assignment schemes along with impairment constraint based routing (ICBR) is proposed which minimizes the effect of four wave mixing and network delay in WAN. Results have been obtained for 8 and 16 equally spaced channels and observed that for equally spaced channels, in comparison with adjacent-next channel assignment scheme the proposed channel assignment scheme gives improvement in the results in terms of lower power of FWM products and lower number of in-band FWM products. Unlike existing channel assignment schemes the algorithm is simple and there is no need to calculate the FWM effect for each channel before assigning it hence reduction in network delay. Calculations have been obtained for point to point multi-fiber link of 1000 km, when power launched per channel is 1 mW for amplified wavelength convertible WAN with amplifier placement of 50 km apart.     

Twin-Ring Optical WDM-MAN Enabling Triple-Hierarchical Reconfigurations and Quadruple-Shared Protections

An optical wavelength division multiplexing metro access network is proposed in this paper. With the design of flexible distribution node (FDN), three kinds of reconfigurable networks can be flexibly built to achieve intra- and inter-optical network unit (ONU)-direct communications. With the adoption of multiple tangent twin-ring topologies, four-level shared protections covering both feeder and distribution fibers are also supported. Moreover, the network can be smoothly expanded by adding express ONUs connected to FDNs. Thus, the network can not only achieve capacity increasing but also support full-duplex reconfigurable communication. A reconfigurable transmission algorithm is also set to avoid wavelengths conflict.     

Effect of line coding on jitter and initial laser phase on Q value in soliton transmission

In this paper we described how different line coding techniques vary with values of jitter in soliton transmission system. Then the idea of this soliton transmission system is applied for multiuser structure and effects of initial line phase spacing are examined.