WDM Optical Switching Research Articles

Study on Influence Factors of Nonlinear Finite Element Analysis for High Arch Dams

In communication network, WDM optical backbone network has become the primary long-distance options. In this paper, the structure of WDM optical networks are analyzed, the add-drop system in the architecture of WDM optical networks is discussed. In order to improve network efficiency, we analyzed the characteristics of network routing, and proposed a new routing design method. In communication network, a good routing is very important for network operation. Routing technologies manage the flow of data between network segments in optical communication network. In addition, we also discussed the WDM optical network switching technology.

Optimal Packet Scheduling in WDM Optical Switches With Output Buffer and Limited Wavelength Conversion

All-optical packet switching is a promising candidate for future high-speed switching. However, due to the absence of optical random access memory, the traditional Virtual Output Queue (VOQ) based input-queued switches are difficult to implement in the optical domain. In this paper we consider output-buffered optical packet switches. We focus on packet scheduling in an output-buffered optical packet switch with limited-range wavelength conversion, aiming at maximizing throughput and minimizing average queuing delay simultaneously. We show that this problem can be converted to a minimum cost maximum network flow problem. To cope with the high complexity of general network flow algorithms, we present an algorithm that can efficiently find an optimal schedule in O(min{NW,BW}) time, where <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</i> is the switch size, W is the number of wavelength channels per fiber and <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">B</i> is the length of the longest FDL at the output of the switch. The complexity of the new algorithm asymptotically matches the lower bound of the scheduling problem. We also conduct extensive simulations to test the performance of the proposed scheduling algorithm under different traffic models.

A novel collision free WDM optical switching network

To avoid burst collision in OBS-WDM ring network, a novel scheme called Estimated Traffic based Longest Queue First (ETLQF) has been proposed. In it, the scheduler considers both the queue length and the incoming traffic. The scheduler can adjust the queue lengths in advance to cater to the incoming traffic, targeting to reduce cell loss ratio (CLR) and improve the buffer utilization. The simulation results show that the ETLQF in OBS ring networks not only reduces CLR by 10–60%, but also achieves high throughput while saving 65% of wavelengths, when compared to conventional schemes with only destination delay.

Multipath traffic engineering in WDM optical burst switching networks

In this paper, we investigate the problem of multipath traffic engineering in optical burst switching (OBS) networks. The main goal of this work is to minimize burst loss rate in the network by adaptively balancing the burst traffic among multiple paths based on the measurement and analysis of path congestion. We develop three distributed traffic splitting algorithms by considering the special features of OBS networks. Among these three algorithms, one algorithm considers burst level traffic distribution, and the other two algorithms consider flow level traffic distribution to avoid packet reordering problem. The proposed multipath traffic engineering algorithms achieve significant performance improvement in reducing burst loss probability in a distributed manner in OBS networks. Further, through theoretical analysis and simulations, we show that the proposed algorithms converge quickly on a sudden traffic increase in the network.

Achieving multi-class service differentiation in WDM optical burst switching networks: a probabilistic preemptive burst segmentation scheme

We propose a Probabilistic Preemptive Burst Segmentation (PPBS) scheduling scheme to provide priority classes with different Quality-of-service (QoS) requirements in WDM Optical Burst Switching (OBS) networks. The PPBS scheme enables high priority bursts to preempt and segment low priority bursts in a probabilistic fashion. The PPBS scheme achieves 100% isolation among priority classes, and burst loss probabilities can be controlled by tunable parameters. Our PPBS queueing model also implicitly enables us to obtain several results related to the Erlang's loss function which may be useful in the role of this function arising in some areas of queueing theory, as well as characterizing a loss rate region that work conserving burst scheduling techniques can achieve. As an application to providing service differentiation, we show how the PPBS scheme can minimize the total sum of loss rates and achieve proportional loss differentiation. Finally, we also demonstrate the effectiveness of the PPBS scheme empirically using realistic Internet traffic model, e.g., long range dependent traffic model.

Effects of Crosstalk in WDM Optical Label Switching Networks Due to Wavelength Switching of a Tunable Laser

Crosstalk caused by switching events in fast tunable lasers in an optical label switching (OLS) system is investigated for the first time. A wavelength-division-multiplexed OLS system based on subcarrier multiplexed labels is presented which employs a 40-Gb/s duobinary payload and a 155-Mb/s label on a 40-GHz subcarrier. Degradation in system performance as the transmitters switch between different channels is then characterized in terms of the frequency drift of the tunable laser

Applications of Nonlinear Effects in Highly Nonlinear Photonic Crystal Fiber to Optical Communications

Unique dispersion characteristics and enhanced nonlinearity make the small-core photonic crystal fiber (PCF) an ideal candidate for nonlinear optical devices to telecommunication applications. Some technical reasons behind great research interest of highly nonlinear PCFs in optical communication components are reviewed. Nonlinear effects in highly nonlinear PCFs and their research progress are presented. Several typical applications including WDM sources, optical amplification, optical switching, wavelength conversion, optical regeneration and all-optical demultiplexing etc are introduced, together with state-of-the art performances. Some new possible applications and future prospects are discussed.

FLC SLM을 이용한 편광의존형 2×2 광스위치

We demonstrated a polarization dependent type 2<TEX>$\times$</TEX>2 optical switch, using a binary reflection type SLM. Reflection type FLC was used as a half wave retardation plate. Two inputs were controlled by each SLM for the desired output direction. In conclusion, in the "1" state the average optical loss was 6.6 ㏈, and in the "0" state the average optical loss was 14.6 ㏈, and measured the switching speed as 75 <TEX>$mutextrm{s}$</TEX>. By using this method, a polarization dependent type 2<TEX>$\times$</TEX>2 optical switch can be demonstrated and the possibility of a 4-port WDM optical switch also verified.