This paper presents a comparison study of average queuing delay performance between slotted and unslotted all-optical packet-switched metropolitan area network (MAN) configured as star physical topology. After studying the average queuing delay performance of the two networks which are both equipped with infinite optical buffers, we research the relationship between average queuing delay and the number of optical buffers in the networks equipped with finite fiber delay lines. Considering the complexity of exact solution, we give an approximate solution. By using mathematical expressions and figures, we give the following main results: (a) for a network equipped with finite optical buffers, there exists a maximum average queuing delay; (b) when the numbers of fiber delay lines that are respectively equipped to slotted and unslotted network is same, the maximum average queuing delay of unslotted network is bigger than that of slotted network; (c) there exist the best N1 and N2 (the number of optical fiber delay lines), which can bring on the best average queuing delay performance of slotted network that is equipped with finite optical buffers.

The proliferation of fiber optic technologies and rapid improvement in component price to performance ratio has opened a wide space for architecting metro scale optical networks. At the same time, the recent slowdown of the telecommunication industry has made it difficult for equipment vendors to differentiate themselves while still meeting the cost objectives. In this presentation, we review the architectures and technologies used to construct metro optical networks and discuss the implications of recent component development on network architectures. The trade-offs of different approaches will be compared.

Today's Metro networks are facing the challenge to transport different services like 2.5 Gbit/s and 10 Gbit/s SDH, Gigabit and 10G Ethernet, and different data formats at costs as low as possible. Particularly due to cost and associated performance reasons wavelength-division multiplex (WDM) transmission systems are an attractive candidate for the Metro area e.g. offering different services over different wavelengths. However, for cost-reduction it is mandatory to avoid expensive components like optical amplifiers (OAs) and dispersion compensating modules (DCMs) whenever possible. This leads to a limited extension of the transparent reach due to e.g. transmitter and receiver characteristics, fiber dispersion, and fiber nonlinearity. It is the object of this paper to investigate the potential of Metro WDM systems and to derive design guidelines without use of OAs and DCMs. Based on computer simulations different fiber infrastructures like Standard Single-Mode Fiber (SSMF, ITU-G.652), positive and negative dispersion Non-Zero Dispersion Shifted Fibers (NZDSF) are analyzed with respect to 2.5 Gbit/s and 10 Gbit/s data rate per channel with low-cost direct and chirp-free external modulation at both data rates. Non-Return-to-Zero- (NRZ-) intensity-modulation is assumed as standard modulation format. At 10 Gbit/s single channel transmission external modulation over pure SSMF results in transmission length of about 50km. Only for high-input powers fiber nonlinearity partly compensates the fiber dispersion and allows an increase in reach up to 90km. For WDM transmission the performance is limited by Self-Phase Modulation (SPM) and Cross-Phase Modulation (XPM) allowing 40x10 Gbit/s uncompensated low-cost transmission over 50km of existing SSMF.

In this paper we present concepts and field trails of automatically switched DWDM networks (ASON). One test network was part of the German field trial "KomNet". The other network is developed and will be tested in the "CAPRICORN" project, a project in the framework of IST (European Community). We focus our investigations on the photonic layer and show results of our experiments on the performance of the network control plane. Each testbed consists of 4 optical cross connects (OXC) in an optically meshed network configuration for the metropolitan and regional area. The main goals are to demonstrate in the field an optical network managed by a control plane and to investigate the functionality of automatically switched transparent optical networks.

An ITU G.652.C-compliant low water peak (LWP) single-mode fiber used with low-cost, full-spectrum, coarse wavelength division multiplexing (CWDM) transmission system [ ] optimizes bandwidth and distance reach for moderate bandwidth, un-amplified, metro/access networks. In this work, we used low-cost active and passive full spectrum CWDM devices to achieve 16-channel error-free transmission (1310 nm - 1610 nm) at 2.5 Gb/s per channel over 50 km of LWP fiber. The aggregate capacity of 40 Gb/s is 33% greater than standard fibers with inherently higher attenuation at 1383 nm. At 50 km, ITU G.652-compliant standard single-mode fiber excessively attenuates the four channels between 1370 nm and 1430 nm. Additional testing utilizing Avalanche PhotoDiode (APD) receivers is demonstrated to extend the LWP fiber distance reach to nearly 70 km [ ] for all 16 channels between 1310 nm and 1610 nm. The transmission equipment included 16 un-cooled distributed-feedback (DFB) laser transceivers and a pair of 16-channel mux/demux modules. All 16 channels showed Q-factors (20logQ) exceeding 18 dB over 50 km of LWP fiber, corresponding to a BER well below 10-15. The standard single-mode fiber exhibited excess loss near 1383 nm, resulting in failure of three channels due to receiver shutdown, with a fourth channel performing at marginal operation with a bit error rate (BER) of 10-9. The dispersion power penalty was negligible for O-band (1260 nm - 1360 nm) channels, increasing to about 1 dB for L-band (1565 nm - 1625 nm) [ ] channels. Robust, error-free operation was achieved for ambient temperatures up to 50 °C for representative channels across the CWDM bands from 1310 nm to 1610 nm. These results demonstrate that a G.652.C, LWP fiber enables optimal transmission distance and optimizes low-cost transmission technology [4] for moderate bandwidth, un-amplified, metro/access networks through full-spectrum CWDM with an aggregate capacity of 40 Gb/s.

Optical technology has brought about altogether new paradigms in the networking field and created an immense momentum in the telecommunications market. Optical component technologies are now enabling the development and deployment of advanced, optical solutions for many networking needs. Overall, there have been some major trends towards optical networks comprising ring/mesh-routed topologies, and connection management intelligence. One of the key challenges to the evolving optical transport network (OTN) is network survivability; how traffic can be protected in OTN with survivability levels equivalent to those achieved in todays SONET/SDH networks. In this article, we focus on metro optical network protection. We begin with an overview of metro optical transport network survivability requirements, followed by an analysis of various network protection mechanisms and how these mechanisms may evolve to support the development of metro optical networks. The benefits of using ring protection scheme in metro optical networks are demonstrated.

In to day's access network, the challenges are current access technologies. We've built networks that are driven by bandwidth, both in the enterprise, on the campus, and in the carrier networks. On enterprises, we're delivering 100 megabits to the desktop. We're delivering gigabit uplinks, multi-gigabit switches at the core. On the other side, in the core carrier networks, the optical revolution of the past a few years has exploded the bandwidth capabilities almost at unimaginable rates. The challenge, though, is between that high bandwidth core network and our high bandwidth campus distributions, the wide area networks are still based on the technologies of the early '90s and even late '80s. We're bandwidth limited by El/Ti 5, by lowspeed ATM and frame relay networks, and they've driven us to a computing model that doesn't deliver the value the organizations need today. Here we propose the optical Ethernet to solve this problem. The fundamental definition of Optical Ethernet is based on taking the power of the Ethernet, that's evolved in the enterprise, and combining it with the power that we delivered in those core service provider optical networks, and putting them together to redefine the access network and the network end-to-end. The Optical Ethernet has the characteristics of the campus in terms of performance and speed and of service provider networks in terms or reliability and multi-site support. Enterprises can build private Optical Ethernets or use a service provider managed service, or a mixture of these two options. Optical Ethernet can be deployed on a MAN or WAN basis between major cities.

A high-performance metropolitan area network has been designed with the combination of coarse wavelength division multiplexing (CWDM) and electrical time division multiplexing (ETDM) techniques. The network consists of n access nodes with each node transmitting and receiving m wavelengths. Virtual multi-channel (VMC) has been achieved at each wavelength via ETDM technique to minimize the data blocking possibility. This network structure has high bandwidth, low communication latency and high performance-to-cost ratio. A prototype network of 6 access nodes has been implemented with 4 virtual channels at each wavelength. The data transmission speed at each wavelength is 1.25 Gbit/s. It can be upgraded to 2.5 Gbit/s. The network has high flexibility and scalability. To further expand the network capacity, multi-wavelength window CWDM technique can be adopted at 1300 nm and 1550 nm simultaneously.

Data services are a primary target for increasing carrier revenues. As carriers prepare to capture this opportunity, they must determine how to cost-effectively deliver the more flexible and scalable bandwidth customers are requesting. Ethernet has emerged as a key technology for delivering these next-generation services; it is easy-to-use, widely understood and offers lower cost to both carriers and end customers. With more bandwidth available in the carrier core, the next challenge is the Metropolitan Area Network (MAN), where data services have been constrained by technologies optimized for voice services. This paper describes an Ethernet-over-SDH/SONET migration scenario that enables a portfolio of metro data services, such as Internet access and Virtual Private Lines, which can be delivered. It illustrates how optimizing SONET/SDH networks for next-generation data services will prove to be more cost-effective, scalable, manageable and resilient.

IEEE's 802.3ah (Ethernet in the First Mile task force) is concentrating on a standard aimed at making optical access affordable and ubiquitous. Subscribers will be able to get 1 Gb/s bi- directional capacity to the central offices. This Gigabit passive optical network (PON) system implies the use of low-cost opto-electronics and standard single-mode fibers. Historically, dispersion of single-mode fibers in these systems has not been an issue due to the relatively low data rates and limited distance. However, for optical Ethernet access, distances up to 20 km and extended temperature ranges are being considered. Therefore, there are now system limitations due to various dispersion penalties. This paper explores the fundamental issues of dispersion and its impact on the access network from a statistical point of view.

The structure of a chip, which maps 10/100 Mbit/s Ethernet fames into SONET/SDH virtually concatenated VC-12 payloads, is put forward. The required link capacity to satisfy the desired QoS is calculated. A closed-loop flow control mechanism for both local and remote ends is suggested and the buffer size under self-similar traffic is estimated

The main goal of this article is to introduce the considerations for developing the All Optical Ether and the successful Base-band Optical Ether Demonstration Experiment we did last year. Besides, some application considerations and comparisons with existing PON are briefly stated as well.

EPON (Ethernet Passive Optical Network) is a new technology for access network based on Ethernet protocol. In this paper, a system model is established to simulate the EPON system. The different noise sources that affect the system performance are taken into account, including 1ST, MIPN, RIN, Extinction Ratio, etc. Not only the system performance degradation induced by burst-mode reception but also the requirement and effect of FEC are considered. The optimal system parameters are found to achieve a tradeoff between system performance and cost. At last, a technical scheme technically and economically feasible for China is put forward. More attention is paid to the burst mode operation which leads to the system performance degradation. A theoretical model is adopted to determine the sensitivity penalty caused by burst mode reception.

Synchronization is one of the difficult problems in realization of Ethernet PON receiver, because the bit rate is as high as 1 .25Gb/s and the receivers works in burst mode. Burst mode synchronization relates to two key techniques: ranging and phase adjustment. For these two key techniques, this paper puts forward a ranging flow for the Ethernet PON system and a novel burst mode synchronization circuit running at 1.25Gbps. Using VHDL, the algorithm and the structure of ranging could be realized, and the result of simulation is provided. The performance of the ranging flow is compared for the different collision resolution algorithm. At the same time, the feasibility and the performance of a high speed burst synchronization circuit are presented with the simulation result.

An algorithm to improve the bandwidth utilization for EPON by using dynamic bandwidth distribution is put forward. System performance, such as queuing delay under self-similar traffic, is simulated by using OPNET.

In this paper, we proposed the request-counter MAC protocol for a broadband access network using an ATM-PON supporting CBR/rtVBR, nrtVBR, UBR and ABR traffic. For this, we present grant field format, minislot format, and dynamic bandwidth allocation algorithm. The proposed MAC protocol applies the different priority to permit distribution process. CBR/rtVBR traffic, with the stringent requirements on CDV or delay, is allocated prior to any other traffic class. nrtVBR traffic such as Internet traffic, which has non-strict CDV or delay criteria, uses flexibly the available bandwidth. UBR traffic is allocated with lowest priority for the remaining capacity. The performance of proposed MAC protocol is evaluated in terms of 1-point CDV with various offered load. From the simulation result, we have confirmed that our proposed scheme can reduce the average cell delay in comparison to that of conventional MAC schemes.

A two-level bidirectional path-protected ring (BPR) architecture for the dense wavelength division multiplexing/subcarrier multiplexing (DWDM/SCM) broadband fiber-wireless access network is proposed and experimentally verified. This architecture can perform self-healing function that utilizes a distributed controller placed at each remote node (RN) and each concentration node (CN) under link failure. If fiber cut occurs between two RNs or CNs, two separate rings are constructed and the up/downstream signals can be delivered adequately. Consequently, the BPR is a reliable architecture for fiber-wireless network. Moreover, we employ a 16-quadrature amplitude modulation (16-QAM) modulated scheme to achieve better spectral efficiency on both up/downstream subcarrier channels. The data rate for each channel is up to 12 Mbit/s for a 3 MHz bandwidth. According to simulated and analyzed results, this architecture can provide large bandwidth, high reliability and excellent flexibility for future broadband wireless networks. Finally, we set up an experimental fiber-wireless network to demonstrate the feasibility of the proposed architecture.

The free-space optical (FSO) communication technology has the advantages of broadband, high-security, immunity to radio, low cost and license-free, etc. It has become a good solution for the "last-mile" access networks. In this paper, We give an outline for designs of the transmitter and receiver circuits, as well as the optical system. The technical parameters calculations of a particular FSO system are also presented.

In this paper, we have analyzed and simulated the BER performance of a turbo coded optical code-division multiple-access (TC-OCDMA) system. A performance comparison has been made between uncoded OCDMA and TC-OCDMA systems employing various OCDMA address codes (optical orthogonal codes (OOCs), Generalized Multiwavelength Prime codes (GMWPC's), and Generalized Multiwavelength Reed Solomon code (GMWRSC's)). The BER performance of TC-OCDMA systems has been analyzed and simulated by varying the code weight of address code employed by the system. From the simulation results, it is observed that lower weight address codes can be employed for TC-OCDMA systems that can have the equivalent BER performance of uncoded systems employing higher weight address codes for a fixed number of active users.

Spatial Reuse can significantly increase the throughput of optical ring networks by allowing multiple stations to transmit concurrently over distinct segments of the ring. Buffer Insertion Ring (BIR) scheme is widely used to achieve spatial reuse. However, because non-preemptive priority is usually given to the ring (pass-through) traffic, BIR scheme may cause fairness problems in allocating the ring bandwidth among distinct nodes. In this paper, we propose a novel approach that can prevent starvation and maximize the throughput with low complexity. The main idea of this method is that for every node of the ring to provide a separate queue for each source that shares the output link of the particular node. We then fairly allocate the output link bandwidth to all the sources based on the weight of the corresponding queues. Simulations and analysis show that this new scheme can provide fairness with less end-to-end delay compare to BIR scheme.

Ethernet is being groomed as the ISP WAN media protocol of the future, both for home users and the corporate market. The need to develop a standard for Ethernet in the first mile (EFM) was given enthusiastic endorsement by main access equipment providers. Ethernet solutions in the first mile enable designers of hardware systems to use the installed base of 300 million Ethernet ports and merchant industry of chipsets and optics. Standardization efforts for this emerging technology are already underway. This paper describes the media access control (MAC) design for the tree-topology Ethernet Passive Optical Network (EPON) system.

ATM based passive optical networks can provide broadband services as defined by the international telecommunication union. The medium access control protocol is of great importance to the access scheme as it controls the flow of traffic in the access network. This paper presents a novel MAC protocol with the ability of traffic profile distortions control for APON system at low cost of bandwidth consumption. We evaluate the protocol performance in the term of cell transfer delay and cell delay variation at different traffic load by computer simulations, which approve the validity of the protocol and the bandwidth allocation algorithm.

Coarse wavelength-division multiplexing (CWDM) is an ideal solution to the tradeoff between the cost and the capacity. Compared with DWDM, CWDM system deploys uncooled distributed feedback (DFB) lasers and wideband optical filters. These technologies provide several advantages to CWDM systems such as lower power dissipation, smaller size and less cost. For these merits mentioned above, the CWDM system will be widely used in the metro and access networks in the future. The CWDM system is scalable, but the scalability is limit. So, in some metro networks, it can¡¯t meet the increasing needs of the capacity. To solve this problem, there are a few of solutions proposed now, such as the TDM techniques and the combination with the DWDM that is applied in C band. In this paper, firstly, we will introduce the techniques of the CWDM, and explain the reasons of the less cost, and then the solutions to the scalability are presented in detail. At last we introduce the applications in the metro and access networks at present.

The recent increase in the transmission speed and bandwidth has resulted in the emergence of new networking solution, Resilient Packet Ring. In this paper, we firstly study the spatial reuse protocol in Resilient Packet Ring. Then based on node model, we discuss several access control mechanisms, including traffic shaping and Virtual Destination Queuing. Finally, a new effective fairness algorithm is presented. In order to ensure the requirement of high priority traffic and avoid high priority traffic taking up all of capacities, the algorithm proportionally assigns the fair rate to different traffic in a theoretical optimal way according to the service priority.

The IEEE 802.1D STP is a kind of layer 2 link management protocol which provides path redundancy while preventing undesirable loops in the network. And it is based on all spanning tree protocols using an algorithm that calculates the best loop-free path through the network. The IEEE 802.1W RSTP provides rapid convergence comparing to 802.1D STP and the IEEE 802.1S MSTP allows frames assigned to different VLANs to follow separate paths, each based on an independent Multiple Spanning Tree Instance, within Multiple Spanning Tree Regions composed of LANs and or MST Bridges offering RSTP feature. These regions and the other Bridges and LANs are connected into one common spanning tree about three types of STPs.

A laboratory experiment was evaluated on the CWDM/GbE Metro Network System. The system is configuration with the optical fiber Coarse Wavelength Division Multiplexing (CWDM) devices that are designed for Metropolitan and Access Area Network. CWDM devices can support 8 channels over a single fiber either a uni- directional or bi-directional mode, and can increase fiber capacity from 2 to 16 times transmission capacity. The system performance was evaluated using the network performance analyzer by measuring the characteristics of throughput and latency. The systems test results showed that this CWDM based Gigabits Ethernet have good transmission performance through the distance to 50 Km.