A heuristic for placement of limited range wavelength converters in all-optical networks

Wavelength routed optical networks have emerged as a technology that can effectively utilize the enormous bandwidth of the optical fiber. Wavelength converters play an important role in enhancing the fiber utilization and reducing the overall call blocking probability of the network. As the distortion of the optical signal increases with the increase in the range of wavelength conversion in optical wavelength converters, limited range wavelength conversion assumes importance. Placement of wavelength converters is a NP complete problem [K.C. Lee, V.O.K. Li, IEEE J. Lightwave Technol. 11 (1993) 962-970] in an arbitrary mesh network. In this paper, we investigate heuristics for placing limited range wavelength converters in arbitrary mesh wavelength routed optical networks. The objective is to achieve near optimal placement of limited range wavelength converters resulting in reduced blocking probabilities and low distortion of the optical signal. The proposed heuristic is to place limited range wavelength converters at the most congested nodes, nodes which lie on the long lightpaths and nodes where conversion of optical signals is significantly high. We observe that limited range converters at few nodes can provide almost the entire improvement in the blocking probability as the full range wavelength converters placed at all the nodes. Congestion control in the network is brought about by dynamically adjusting the weights of the channels in the link thereby balancing the load and reducing the average delay of the traffic in the entire network. Simulations have been carried out on a 12-node ring network, 14-node NSFNET, 19-node European Optical Network (EON), 28-node US long haul network, hypothetical 30-node INET network and the results agree with the analysis. (C) 2001 Elsevier Science B.V, All rights reserved

Priority based dynamic lightpath allocation in WDM networks.

Internet development generates new bandwidth requirement every day. Optical networks employing WDM (wavelength division multiplexing) technology can provide high capacity, low error rate and low delay. They are considered to be future backbone networks. Since WDM networks usually operate in a high speed, network failure (such as fiber cut), even for a short term, can cause huge data lost. So design robust WDM network to survive faults is a crucial issue in WDM networks. This thesis introduces a new and efficient MILP (Mixed Integer Linear Programming) formulation to solve dynamic lightpath allocation problem in survivable WDM networks, using both shared and dedicated path protection. The formulation defines multiple levels of service to further improve resource utilization. Dijkstra\u27s shortest path algorithm is used to pre-compute up to 3 alternative routes between any node pair, so as to limit the lightpath routing problem within up to 3 routes instead of whole network-wide. This way can shorten the solution time of MILP formulation; make it acceptable for practical size network. Extensive experiments carried out on a number of networks show this new MILP formulation can improve performance and is feasible for real-life network. Source: Masters Abstracts International, Volume: 43-01, page: 0249. Adviser: Arunita Jaekel. Thesis (M.Sc.)--University of Windsor (Canada), 2004

Heuristic for the design of fault tolerant logical topology.

Wavelength division multiplexing (WDM) in optical fiber networks is widely viewed as the savior for its potential to satisfy the huge bandwidth requirement of network users. Optical cross connect (OCX) in WDM network facilitates the switching of signal on any wavelength from any input port to any output port. As a result, it is possible to establish ligthpaths between any pair of nodes. The set of lightpaths established over fiber links defines logical topology. In our thesis, we proposed a heuristic approach for the design of fault tolerant logical topology. Our design approach generalizes the design protection concept and enforces wavelength continuity constraint in a multi-hop optical network. In our work, we first designed logical topology for fault free state of the network. We, then, added additional lightpaths for each single link failure scenario. Numerical results clearly show that our approach outperforms Shared path protection and Dedicated path protection. Our simulation result shows that our approach is feasible for large networks. (Abstract shortened by UMI.) Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis2005 .S24. Source: Masters Abstracts International, Volume: 44-03, page: 1413. Thesis (M.Sc.)--University of Windsor (Canada), 2005

Inside all-optical networks

Imagine a world where lightning speed Internet is as common as telephones today. Imagine when light, the fastest moving thing in the universe, is the signal-carrying transport medium. Imagine when bandwidth no more remains a constraint for any application. Imagine when imagination is the only limit! This all can be made possible with only one technology and that is optical communication. Optical networks have thus far provided a realization to a greater extent to the unlimited bandwidth dreams of this era, but as the demands are increasing, the electro-optic conversions seem to become bottlenecks in blended optical networks. The only answer to this is a complete migration to `All-Optical Networks\u27 (AONs) which promise an end-to-end optical transmission. This thesis will investigate various aspects of all-optical networks and prove that AONs perform better than currently existing electro-optical networks. In today\u27s\u27 electro-optical networks, routing and switching is performed in electronic domain. Performance analysis of electro-optical and all-optical networks would include node utilization, link utilization and percentage of traffic routed. It will be shown through Opnet Transport Planner simulations that AONs work better under various traffic conditions. The coming decade will see a great boom in demands on telecommunications networks. The development in bandwidth-hungry applications like real-time video transmission, telemedicine, distance learning and video on demand require both an unlimited amount of bandwidth and dependable QoS. It is well understood that electrically switched networks and copper cables will not be able to meet the future network demands effectively. The world has already agreed to move towards optical communication techniques through the introduction of fiber in access parts of the networks replacing copper. Now the race is to bring optics in higher layers of OSI reference model. Optical communication is on the horizon, and new discoveries are still underway to add to the value of available bandwidth through this technology. My research thesis will primarily focus on the design, architecture and network properties of AONs and challenges being faced by AONs in commercial deployment. Optical components required in AONs will be explored. A comparison between AONs and electro-optical networks will also be shown through optical transport planner simulations

A tunable-channel multi-access wavelength division multiplexed network and surveillance schemes for optical cross-connects.

by Eddie Ting Pong Kong.Thesis (M.Phil.)--Chinese University of Hong Kong, 1999.Includes bibliographical references (leaves 61-68).Abstracts in English and Chinese.Chapter 1 --- Introduction --- p.1Chapter 1.1 --- Optical Network Architecture --- p.1Chapter 1.2 --- High-Speed All-Optical Tunable-Channel Multi-Access Networks --- p.3Chapter 1.3 --- Fault Surveillance of Optical Cross-Connects in Wavelength Routing Network --- p.3Chapter 1.4 --- Outline of the Thesis --- p.5Chapter 2 --- Optical Multi-Access Networks --- p.6Chapter 2.1 --- All-Optical Networks --- p.6Chapter 2.2 --- Optical Multi-Access Schemes --- p.8Chapter 2.2.1 --- Wavelength-Division Multi-Access (WDMA) --- p.9Chapter 2.2.2 --- Time-Division Multi-Access (TDMA) --- p.12Chapter 2.2.3 --- Subcarrier Multi-Access (SCMA) --- p.14Chapter 2.3 --- Design Considerations --- p.14Chapter 3 --- All-Optical Tunable-Channel Multi-Access Networks --- p.18Chapter 3.1 --- Tunable-Channel Multi-Access Networks --- p.19Chapter 3.2 --- Protocols for TCMA Networks --- p.20Chapter 3.3 --- Photonic Implementation of a Wavelength Division TCMA Network with Time- Slot Access --- p.23Chapter 3.3.1 --- Proposed Network Architecture --- p.25Chapter 3.3.2 --- Experimental Results --- p.30Chapter 3.3.3 --- Discussion --- p.34Chapter 3.3.4 --- Summary --- p.35Chapter 4 --- Fault Surveillance for Optical Cross-Connects in Wavelength Routing Networks --- p.36Chapter 4.1 --- Wavelength Routing Networks --- p.37Chapter 4.2 --- Options in Fault Surveillance --- p.39Chapter 4.3 --- Optical Path Surveillance of Optical Cross-Connects in Wavelength Routing Networks --- p.41Chapter 4.3.1 --- Scanning Amplified Spontaneous Emission Identification Surveillance Scheme --- p.43Chapter 4.3.2 --- Pilot-Tone Based Surveillance and Removal Scheme --- p.49Chapter 4.4 --- Summary --- p.55Chapter 5 --- Conclusion --- p.57Chapter 5.1 --- Summary of the Thesis --- p.57Chapter 5.2 --- Future Work --- p.60Bibliography --- p.61Publication List --- p.5

Providing Survivability In Optical Wdm Mesh Networks Considering Adaptation

Tez (Yüksek Lisans) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2007Thesis (M.Sc.) -- İstanbul Technical University, Institute of Science and Technology, 2007Internet kullanımının artışı ile birlikte, hızla büyüyen bant genişliği isteklerini karşılayabilecek olan optik WDM ağları, gelecekteki en uygun Internet omurgaları haline gelmiştir. Oluşabilecek herhangi bir bağlantı hatası, o bağlantı üzerinden geçen tüm ışık yollarının başarısızlığına yol açabilir. Bu yüzden, optik WDM ağları etkili hata bağışıklığı yöntemlerine ihtiyaç duymaktadır.Optik WDM ağlarındaki hata bağışıklığı problemini etkili bir şekilde giderebilmek için son günlerde bir çok yöntem sunulmuştur. Bu yöntemler arasında paylaşılan yol ile koruma yöntemi etkin kaynak kullanımı sağlayabildiğinden, en umut verici yöntemlerden biri olarak görülmektedir. Bu yöntemde yedek ışık yolları, eğer ilişkili birincil ışık yolları karşılıklı olarak farklı ise yani ortak bağ kullanmıyor iseler, dalga boyu paylaşımı yapabilemekdirler. Bu özelliğinden dolayı paylaşılan yol ile koruma yöntemi, yedek ışık yollarına daha az kaynak ayrılmasını sağlar ve diğer koruma yöntemlerinden daha iyi performans gösterir. Bu çalışmada, bir optik WDM ağına dinamik olarak gelen bağlantı isteklerine cevap verilirken, paylaşılan yol ile koruma ve yeniden yönlendirme özelliğini kullanan etkili bir yöntem geliştirilmiştir. Adaptasyon sağlayan paylaşılan yol ile koruma yöntemi olarak adlandıralan yeni yaklaşım, dinamik trafik akışında yedek yolların yol açtığı fazla kaynak tüketimini azaltmak için zaman içinde ağı yeni durumlara adapte edebilen, etkili yani daha çok isteğe cevap verilebilen bir servis sağlayabilmektedir. Bağlantıların öncelik beklentisine göre yeniden yönlendirme yapma özelliğinden dolayı servis seviyesinde anlaşma sağlayabilen bir yaklaşımdır.WDM optical networks are able to meet the rapid growth of bandwidth demands and are considered to be the most appropriate choice of future Internet backbone. However, the failure of a network component such as a fiber link can lead to the failure of all the lightpaths that traverse the failed link. Therefore, the huge bandwidth of WDM also requires efficient survivability mechanisms. Recently, new techniques have been proposed to efficiently deal with this problem in mesh networks. Among them, shared-path protection is a promising candidate because of its desirable resource efficiency, which is a result from effective backup sharing. Backup paths can share wavelength channels, when their corresponding working paths are mutually diverse. Therefore, shared-path protection can outperform other protection techniques based on the dedicated reservation of backup capacity. In this work, we focus on rerouting feature to design an efficient algorithm, called Adaptable Shared Path Protection (ASPP), for dynamic provisioning of shared-path-protected connections in optical mesh networks employing WDM. In particular, backup-channel capacity reservation in shared-protection causes too much resource consumption parallel to network load. ASPP provides the adaptation of network against dynamic traffic, and decreases blocking probability thanks to rerouting capability of paths. Also, ASPP can present SLA by providing an uninterrupted traffic flow for connection requests come with a high priority.Yüksek LisansM.Sc

Impact of wavelength converters in wavelength routed all-optical networks

This paper attempts to study the impact of wavelength converters in WDM wavelength routed all-optical networks. A new heuristic approach for placement of wavelength converters to reduce blocking probabilities is explored. Multihop virtual topology is designed to minimize the number and overall cost of the converters. Blocking probabilities for Static Lightpath Establishment (SLE) and Dynamic Lightpath Establishment (DLE) are analyzed. In the case of SLE, arranging lightpaths in ascending order of their path length reduces blocking probability. Wavelength converters placed at nodes with high nodal degree further reduces the blocking probabilities. Simulation studies performed on 28-node USA long haul network, 20-node arbitrary mesh network, and 19-node EON (European Optical Network) validate the observations made earlier

NASA SBIR abstracts of 1991 phase 1 projects

The objectives of 301 projects placed under contract by the Small Business Innovation Research (SBIR) program of the National Aeronautics and Space Administration (NASA) are described. These projects were selected competitively from among proposals submitted to NASA in response to the 1991 SBIR Program Solicitation. The basic document consists of edited, non-proprietary abstracts of the winning proposals submitted by small businesses. The abstracts are presented under the 15 technical topics within which Phase 1 proposals were solicited. Each project was assigned a sequential identifying number from 001 to 301, in order of its appearance in the body of the report. Appendixes to provide additional information about the SBIR program and permit cross-reference of the 1991 Phase 1 projects by company name, location by state, principal investigator, NASA Field Center responsible for management of each project, and NASA contract number are included