A method of segment protection based on p-cycle for dynamic multicast with limited-range wavelength converter in WDM network

In the optical multicast network, node and link failures have very important influence on the network survivability which may lead to multiple destinations cannot receive data. Based on the wavelength layered-graph method, a method of efficiency-score based on heuristic algorithm of pre-configured cycle (p-Cycle) based-segment protection (ESHS) for dynamic multicast with limited-range wavelength conversion was presented in this paper. By finding the multicast tree segment protection, the total available p-Cycles are constructed for the multicast. Then we calculate each p-Cycle efficiency-score, the highest efficient-score p-Cycle is selected as the multicast route protection p-Cycle. The simulation results show that the ESHS can get higher performance than the existing ESHT algorithm, in terms of multicast request blocking probability and wavelength utilization.     

WDM-DPSK Systems Based on SOAs in TOSCA Project

Abstract

Using differential phase shift keying, we fully exploit semiconductor optical amplifiers (SOAs) for signal amplification in practical Wavelength Division Multiplexing (WDM) Nx10 Gbit/s unrepeated systems. Record transmission experiments are presented, thus making SOAs a competitive amplification alternative in metro and extended-metro networks.     

Advancements in passive planar lightwave circuits and hybrid integration devices

Planar silica device technology provides the ability to filter, route, switch, and attenuate optical signals for Wavelength Division Multiplexing (WDM) based photonic networks. As network capacity expands there is a requirement to increase the complexity, scale and density of the functions whilst reducing cost. It is also important that both the optical performance and long term stability of the devices are not compromised. The following paper reviews recent progress on these types of devices for large-scale manufacture, concentrating on key performance parameters for filter type structures and hybrid integrated devices such as insertion loss and polarisation dependent loss (PDL). To cite this article: J.R. Bonar et al., C. R. Physique 4 (2003).     

WDM光网络安全生存机制研究

针对WDM光网络安全生存性问题的故障的发现、定位和恢复三个重要环节之中的恢复问题,提出了一种WDM光层中的安全保护与恢复方案。采用了恢复路由选择算法和恢复波长分配算法,提出了一种混合的多层恢复机制,从而构建了一种从故障的发现、定位到故障恢复的覆盖各环节的连续性光网络安全生存机制,并在理论上进行了性能比较。     

An efficient fault localization or detection mechanism for high speed optical networks

Optical burst switching (OBS) has been considered as the gate through which the envisaged world of optical Internet will be conquered by implementing Internet Protocol (IP) software directly over a wavelength-division-multiplexing (WDM) optical layer (IP/WDM). The main feature for designing next generation optical networks is protecting and restoring high capacity WDM networks from the failures. Quick detection, identification and restoration make networks more strong and consistent even though the failures cannot be avoided. Hence, it is necessary to develop fast, efficient and dependable fault localization or detection mechanisms. In this paper, an efficient scheme for OBS networks has been proposed to provide fast restoration of links with minimum delay as well as blocking probability. By simulation results, it is shown that the proposed OBS scheme achieve less blocking probability and delay while getting higher throughput in comparison to conventional schemes.     

Performance of optical links with optical amplifiers

In this work a comparison between the performances of single and multichannel systems is reported for links with optical amplifiers, considering conventional and soliton signals, Time Division Multiplexing (TDM), and Wavelength Division Multiplexing (WM) techniques. The performance evaluation is obtained by means of numerical simulations taking into account the effects of the chromatic dispersion, the Kerr nonlinearity, and the ASE noise of the optical amplifiers. Both the regimes of constant and fluctuating chromatic dispersion along the link are studied. The possibility of implementing high-capacity optical systems for a high-bandwidth European network is evaluated.     

Dynamically selective multiwavelength cross-connect based on fibre Bragg gratings and mechanical optical switches

A dynamically selective multiwavelength cross-connect for wavelength division multiplexed (WDM) networks based on fibre Bragg gratings (FBGs) and optical switches is reported. Dynamically single- or multi-channel cross-connect functionality can be realized according to control of the optical switches and the FBGs' arrangement. Bit-error-rate performance with negligible power penalty is achieved in a 2.5Gbs-1x3 WDM channels over 100km conventional single-mode fibre (SMF) network demonstration. The characteristics of low channel crosstalk, uniform channel loss, high scalability and cascadability, and low cost of this device could provide more reconfiguration flexibility and network survivability for WDM networks.     

A novel full duplex 16 Gbps SCM/ASK radio over fiber WDM-PON sharing wavelength for up- and down-link using bidirectional reflective filter

In this paper, a new bidirectional wavelength division multiplexing radio-over-fiber (WDM-RoF) using Subcarrier Multiplexing/Amplitude Shift Keying (SCM/ASK) is proposed which shares the same wavelengths for both up-link and down-link. A bidirectional reflective filter (BRF) is utilized in the upstream link to provide a reliable bidirectional optical channel. WDM is used to further increase the capacity of system. Simulation of the proposed scheme demonstrates 1 Gbps down- and up-link data stream for 16 channels over the length of 25 km with acceptable Q-factor (>6 dB).     

Low crosstalk monolithic wavelength demultiplexing switch arrays

Wavelength Division Multiplexing (WDM) is a key enabling technology for increasing the transmission capacity of optical fiber communication systems. Recently, a new family of optoelectronic devices, including detectors, switches, and emitters, that is based on resonant cavity enhancement, has emerged. Wavelength selective optoelectronic switching is achieved by placing a photothyristor in an asymmetric Fabry-Perot cavity, which provides a highly selective response at a wavelength determined during device fabrication. These WDM optoelectronic devices haue promising applications in optical COmmunications and optical logic circuits. Results on a N-p-n-p optoelectronic switch with a ten wavelength channel capability are presented.     

Performance evaluation of survivable WDM based SANs in a metro ring network

Storage area networks (SANs) are an essential part of enterprise computing today. There is no comprehensive business continuity plan without SANs in the picture. This paper proposes and evaluates network survivability of optical paths in wavelength division multiplexing (WDM) based storage area networks in a metro ring network. The paper begins with a background on network survivability in metro WDM ring network. Subsequently, the network and node architectures along with their medium access control (MAC) protocols are described. In this work, one link failure (a single cable cut) in metro WDM based SANs in a ring network architecture is considered. Performance evaluation for network survivability in metro WDM SAN is carried out by means of discrete-event computer simulation. Network throughput and packet delay are investigated. The network performance is evaluated for asymmetric (unbalanced) traffic scenarios under Poisson and self-similar traffic.     

PSO算法用于WDM系统多信道PMD补偿的研究

根据波分复用（Wavelength Division Multiplexing,WDM）系统多信道偏振模色散（Polarization Mode Dispersion,PMD）的最坏信道补偿方案,将粒子群优化（Particle Swarm Optimization,PSO）算法用于多信道的PMD补偿.在补偿最坏信道的同时,保障了其他信道的性能.并以两信道PMD补偿系统为例进行了数值模拟,得到了很好的补偿效果.     

Adding channels with PSBT format at 40 Gbit/s in an existing 10 Gbit/s optical network

Until recently, the wavelength-division-multiplexed (WDM) transmission system has reached record capacities and distances due to innovations such as FEC (Forward Error Correction), distributed Raman amplification, new transmission fiber and advanced optical format. Optical-communication systems exclusively employed conventional On-Off Keying signals in either Non-Return-To-Zero (NRZ) or Return-To-Zero (RZ) format. Recently a number of advanced modulation formats have attracted attention. Some of these formats carry information through On-Off-Keying but also modulate the optical phase in order to enhance the robustness of signal to chromatic dispersion, optical filtering and non-linearities. Through extensive sets of simulation results, we showed that it is possible to replace a channel with higher bit-rate on existing DPSK or OOK at 10Gbit/s transmission link. Duobinary formats are ideal candidates to do it and are known for their low spectral range and high tolerance to residual chromatic dispersion. These particularities make them very attractive for both high bit rates and high distance-transmissions. Today, Phase Shaped Binary Transmission (PSBT) is considered as being the promising format for the deployment of 40Gbit/s technology on existing links at 10Gbit/s WDM long haul transmissions.     

Survivability in IP-over-WDM Networks: WDM Lightpath Protection versus IP LSP Protection

Abstract

This article compares the performance of WDM lightpath protection and IP LSP protection schemes for IP-over-WDM networks. A mathematical formulation of the maximum throughput problem is presented and analytical expressions for recovery time are derived for both schemes. The throughputs and recovery times are analyzed and compared. Results show that the IP LSP protection scheme presents higher throughputs then WDM lightpath protection. The IP LSP protection scheme, providing individual IP LSP protection has, however, scalability problems. This scheme presents high recovery times when a failure affects many lightpaths and many hops are allowed for the primary routes of IP LSPs.     

Multicast protection algorithms based on aggregated logical topology in survivable multi-domain optical networks

Since the optical network carries a lot of traffic, the survivability is an important issue to ensure the service continuity. At the same time, with the network scale increasing, the optical network has been divided into multi-domains each of which is managed by a unique network provider. Therefore, the survivability in multi-domain optical networks has got more attention in recent years. However, current works mostly addressed the unicast survivability and few or no solved the multicast survivability in multi-domain optical networks. Therefore, in this paper we propose two heuristic algorithms called Multicast Multi-domain Dedicated Protection (MMDP) and Multicast Multi-domain Shared Protection (MMSP) to provide the survivability in multicast multi-domain optical networks. In MMDP and MMSP, to provide the intra-domain protection, we use the modified Minimal-cost Path Heuristic (MPH) algorithm to compute the intra-domain survivable multicast tree. To provide the inter-domain protection, based on multi-domain logical topology, we firstly use the MPH algorithm to compute the inter-domain logical multicast tree and then use the Dijkstra algorithm to compute the inter-domain logical backup sub-path for each inter-link on this logical multicast tree. Simulation results show that MMSP has better resource utilization efficiency and lower blocking probability.     

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.     

Research trends in terrestrial transmission systems

The technique of wavelength division multiplexing (WDM) has paved the way for multi-terabit/s capacities in terrestrial optical networks. Recently, we conducted a laboratory experiment to emulate a terrestrial transmission of 6.3 Tbit/s capacity over a record 2700 km distance. After describing some of the specific features of optical terrestrial transmission, we discuss the various technologies possibly involved in such an emulator and discuss their implementation in actual systems, namely the modulation format, the optical amplifier scheme, the 40 Gbit/s electronics and the forward error-correcting codes. To cite this article: S. Bigo et al., C. R. Physique 4 (2003).     

Performance comparison of various modulation schemes over free space optical (FSO) link employing Gamma–Gamma fading model

Free Space Optics (FSO) is an emerging line-of-sight technology intending to provide last-mile solution to the network problem where fiber technology is not feasible. The use of Wavelength Division Multiplexing (WDM) technology for FSO is inspired due to the demand for broadband communication. This technique has brought a revolution because the system data capacity is enhanced by simply adding more number of channels and reducing the channel spacing without having the need of more than one FSO link. By reducing the channel spacing to an appropriate level, Dense Wavelength Division Multiplexing (DWDM) based FSO systems are also be attained and are reported by various research works. FSO finds applications in vast areas like backhaul networks for cellular communication, disaster recovery, LAN–LAN connectivity, high-definition TV, MAN-extension, video transmission, medicine industry and surveillance. However, its usage is limited due to the serious challenges of link vulnerability to weather and atmospheric turbulence-induced fading. This paper is based on a WDM-FSO system. An 8-channel WDM based FSO system is proposed and performance is evaluated on widely accepted modulation schemes under weak, moderate and strong turbulence conditions. Gamma–Gamma fading model is employed for atmospheric turbulence modelling. The system is simulated on OptiSystem 14.0.     

Flexible broadcasting and multicasting in 4λ × 10 Gb/s AOPR TWDM PON system

In this letter, we propose a new architecture of Time Wavelength Division Multiplexing Passive Optical Network (TWDM PON) system to support dynamic multi wavelength allocation (DMWA) in both upstream and downstream directions using an integrated semiconductor optical amplifier (SOA) and arrayed waveguide grating (AWG) with multi wavelength select continuous wave (CW) pump probe signal module. The significance of this architecture is the flexible routing function with the capability of multicasting and broadcasting between multiple optical line terminal (OLT) PON port with multiple optical distribution network (ODN) link using a new wavelength tuning free (WTF) OLT transmitter module to eliminate wavelength tuning delay in downstream signal utilizing multicasting Cross Gain Modulation (XGM) wavelength conversion. The experimental results show that 4λ × 10-Gb/s TWDM PON system can be used to connect 4096 users with the conventional fixed wavelength OLT transceivers with 36 dB link loss.     

Novel wavelength-division-multiplexed ring network architecture using optical path technology for multiple services and simple media access control procedure

A novel WDM ring network architecture that employs an attractive integrated-optic arrayed-waveguide grating (AWG) add-drop multiplexer (ADM) is proposed that fully uses a variety of optical path technologies. Single-hopped multiwavelength looped-bus optical paths establish multipoint-to-multipoint (M-M) communication, while conventional ringtype optical paths realize point-to-point and broadcast communication. Optical paths for OAM & C can also be established on a multihop basis with no additional wavelengths. All these optical paths can be established by a simple AWG-ADM in a node. A simple MAC procedure for M-M communication is proposed, and its performance is simulated. This procedure switches between the random with minimum slot distance limitation scheme and the slot assignment scheme. Simulation results confirm its fairness as evaluated by the metric of delay variance and its small delay. Network survivability is realized by the optical loop-back (LB) method.     

Spectrally Efficient 3D Optical CDMA Using Coherent Spatial Phase–Time Coding/Decoding

We demonstrate a WDM compatible optical CDMA system incorporating 3D spectral phase–time encoding/decoding. We provide coding and decoding using binary [0, π] phase chips for six users at 6 Gb/s, with a single coded signal separated with an acceptable bit-error rate ≤10 ^?9. The coding and decoding method is based on 3D coding of tightly spaced phase-locked laser lines that is compatible with conventional WDM networking. In optical CDMA systems, we propose to provide encoding and decoding done by converting Hadamard codes (used for conventional CDMA system) to the phase codes. We report that duo-binary modulation format is the best with adequate bandwidth compression. We confirm that better simulation results are reached in terms of the Q factor and bit error rate.