Showing papers in "Photonic Network Communications in 2001"
TL;DR: This study proposes the design and analysis of a PON architecture which has an excellent performance-to-cost ratio and discusses the possibility of improving the bandwidth utilization by means of timeslot size adjustment, and by packet scheduling.
Abstract: With the expansion of services offered over the Internet, the “last mile” bottleneck problems continue to exacerbate. A passive optical network (PON) is a technology viewed by many as an attractive solution to this problem. In this study, we propose the design and analysis of a PON architecture which has an excellent performance-to-cost ratio. This architecture uses the time-division multiplexing (TDM) approach to deliver data encapsulated in Ethernet packets from a collection of optical network units (ONUs) to a central optical line terminal (OLT) over the PON access network. The OLT, in turn, is connected to the rest of the Internet. A simulation model is used to analyze the system’s performance such as bounds on packets delay and queue occupancy. Then, we discuss the possibility of improving the bandwidth utilization by means of timeslot size adjustment, and by packet scheduling.
349 citations
TL;DR: New weight functions are presented that exploit the strong correlation between blocking probability and number of hops involved in connection setup to increase the performance of the network and show the best performance in terms of blocking probability.
Abstract: Optical dense wavelength division multiplexed (DWDM) networks are an attractive candidate for the next generation Internet and beyond. In this paper, we consider routing and wavelength assignment in a wide area wavelength routed backbone network that employs circuit-switching. When a session request is received by the network, the routing and wavelength assignment (RWA) task is to establish a lightpath between the source and destination. That is, determine a suitable path and assign a set of wavelengths for the links on this path. We consider a link state protocol approach and use Dijkstra’s shortest path algorithm, suitably modified for DWDM networks, for computing the shortest paths. In [1] we proposed WDM aware weight functions that included factors such as available wavelengths per link, total wavelengths per link. In this paper, we present new weight functions that exploit the strong correlation between blocking probability and number of hops involved in connection setup to increase the performance of the network. We also consider alternate path routing that computes the alternate paths based on WDM aware weight functions. The impact of the weight functions on the blocking probability and delay is studied through discrete event simulation. The system parameters varied include number of network nodes, wavelengths, degree of wavelength conversion, and load. The results show that the weight function that incorporates both hop count and available wavelength provides the best performance in terms of blocking probability.
58 citations
TL;DR: In this article, a new multicast tree construction algorithm is proposed based on a concept called virtual source, where a virtual source is a node having both the splitting and wavelength conversion capabilities.
Abstract: Wavelength-division multiplexed (WDM) networks using wavelength-routing are considered to be potential candidates for the next generation wide-area backbone networks. Multicasting is the ability to transmit information from a single source node to multiple destination nodes and is becoming an important requirement in high-speed networks. As WDM technology matures and multicast applications become increasingly popular, supporting multicast routing at the WDM layer becomes an important and yet a challenging topic. This paper concerns with the problem of optical multicast routing in WDM networks. A few nodes in the network may have wavelength conversion and/or splitting capabilities. In this paper, a new multicast tree construction algorithm is proposed. This algorithm is based on a concept called virtual source. A virtual source is a node having both the splitting and wavelength conversion capabilities. By exploiting the presence of virtual source nodes, the proposed algorithm achieves improved performance. To further improve the performance, the algorithm assigns priorities to nodes based on their capabilities. The effectiveness of the proposed algorithm is verified through extensive simulation experiments.
49 citations
TL;DR: Two approximate analytical models are presented that can be used both for analysis and engineering of the optical buffer and in particular to dimension the buffer time unit in an way that is optimal with respect to packet loss probability.
Abstract: This paper addresses the problem of dimensioning buffers realized by means of fiber delay lines in optical routers able to switch packets that have variable length and are sent asynchronously on the optical links. The optical buffer is analyzed focusing on the different behavior of a delay buffer and an electronic memory. The role of the time unit of the fiber delay lines is discussed, showing that it is a crucial parameter to determine the queuing performance. The paper presents two approximate analytical models that can be used both for analysis and engineering of the optical buffer and in particular to dimension the buffer time unit in an way that is optimal with respect to packet loss probability. The first model is based on an infinite queuing approximation. It is not very accurate and is valid for a limited set of values of the traffic load, but is extremely simple. The second model is based on a finite queuing approximation. It is more complex but more accurate and is valid for any value of traffic load. The accuracy of the models is compared with simulation and their range of applicability purposes is discussed.
46 citations
TL;DR: The results of comparing the two path establishment schemes show that, for dynamically changing traffic, the adaptive selection of wavelengths on a fixed route during path establishment is more beneficial than the optimal selection of the route and wavelengths prior to path establishment.
Abstract: This paper studies algorithms for connection establishment in wavelength division multiplexing networks. Although wavelength conversion capabilities are assumed at each node in the network, the goal of this research is to minimize or impose an upper bound on the number of wavelength conversions on the established path. Two types of schemes are investigated and compared. In the first scheme, the wavelengths are selected adaptively during path establishment on a given route, and in the second scheme, both the route and the wavelength assignment are selected optimally based on global information about path costs and wavelength availability in the network. We present two efficient algorithms for globally selecting routes and wavelengths, one finds the least cost route for a maximum number of wavelength conversions, and the other selects from among the shortest routes, the one with a minimum number of wavelength conversions. The results of comparing the two path establishment schemes show that, for dynamically changing traffic, the adaptive selection of wavelengths on a fixed route during path establishment is more beneficial than the optimal selection of the route and wavelengths prior to path establishment.
46 citations
TL;DR: A dynamically reconfigurable fiber-wireless network using flexible wavelength routing techniques is proposed by the PRISMA project, which offers a “forecast-tolerant” solution for handling a wide variety of wireless services and capacity demands as may emerge in the fast evolving market of mobile communications.
Abstract: A dynamically reconfigurable fiber-wireless network using flexible wavelength routing techniques is proposed by the PRISMA project, which offers a “forecast-tolerant” solution for handling a wide variety of wireless services and capacity demands as may emerge in the fast evolving market of mobile communications. This approach can considerably increase the operation efficiency of wireless networks for broadband nomadic services (wireless LANs). It also supports the evolution from GSM and GPRS towards UMTS, and the entry of new operators and/or services into the liberalized mobile communications market. The system has been implemented in a field trial and has been operated successfully with real users and broadband nomadic services. The system concept is ready for further development into products.
32 citations
TL;DR: The results demonstrate that it is beneficial to use a single-hop approach based on simulated annealing for a small grooming ratio, but for a large grooming ratio and node number, the use of the multihop approach is advocated.
Abstract: To fully utilize the capabilities of a SONET/ADM network, traffic grooming is needed to multiplex a number of lower-rate traffic streams into a higher-rate stream, and vice versa. Although the capacity of a SONET ring network can be upgraded by operating it over multiple wavelengths, the corresponding network design may be costly if it employs a large number of ADMs. A cost-effective design attempts to minimize the total number of ADMs used in the network while carrying the offered traffic. We introduce and evaluate the performance characteristics of two new traffic-grooming approaches for WDM ring networks, called single-hop and multihop. Our single-hop implementation uses the simulated-annealing heuristic. After placing all the traffic on “virtual circles”, we group the circles in order to reduce the number of ADMs in the network. Our multihop implementation places an ADM at each node based on the requested traffic in the traffic-demand matrix; then, it tries to groom the wavelengths which can be groomed. We select one of the nodes to be the “hub” node which has an ADM for each wavelength. The hub node, therefore, can “bridge” traffic between all of the wavelengths. Each algorithm is specified and illustrated by a simple example. Our results demonstrate that it is beneficial to use a single-hop approach based on simulated annealing for a small grooming ratio, but for a large grooming ratio and node number, we advocate the use of the multihop approach.
27 citations
TL;DR: This work improves system performance by using a hidden Markov chain based prediction algorithm to reduce the amount of time spent in computing the schedule by predicting traffic requests and shows that the error of prediction is reasonable for most cases.
Abstract: This paper presents the design and performance analysis of a predictor-based scheduling algorithm for optical wavelength division multiplexed (WDM) networks. WDM technology provides multiple, simultaneous and independent gigabit-per-second channels on a single fiber. A reservation-based multiple access control (MAC) protocol is considered here for a local area WDM network based on the passive star topology. The MAC protocol schedules reservation requests from the network nodes on the multiple channels. In previous work, we have presented an on-line scheduling algorithm for such a network. We have shown earlier that schedule computation time can significantly affect performance and the scheduling algorithms should be simple for better performance. In this work, we further improve system performance by using a hidden Markov chain based prediction algorithm. The objective here is to reduce the amount of time spent in computing the schedule by predicting traffic requests. Performance analysis based on discrete-event simulation, varying parameters such as number of nodes and channels is presented. The results show that the error of prediction is reasonable for most cases: more than 70% of the time, the error between actual request and predicted request is less than 20%. Network throughput is higher with the proposed prediction algorithm due to pipelining of schedule computation.
23 citations
TL;DR: This paper explains how multi-protocol label switching (both electrical and optical) recovery mechanisms can be important to reach that goal and a novel MPLS recovery mechanism called fast topology-driven constrained-based rerouting is presented.
Abstract: Due to the fast increase of Internet traffic and the enormous bandwidth potential of all-optical transport networks based on wavelength division multiplexing, an IP-over-WDM network scenario is likely to be widespread in future communication networks. At the same time, IP networks are becoming more and more mission-critical. Hence, it is of paramount importance for IP-over-WDM networks to be able to recover quickly from frequently occurring network failures. This paper explains how multi-protocol label switching (both electrical and optical) recovery mechanisms can be important to reach that goal. Moreover, a novel MPLS recovery mechanism called fast topology-driven constrained-based rerouting is presented. Different MPLS recovery mechanisms are compared to each other. Special attention hereby goes to the additional capacity that is required to recover from frequently occurring failures.
22 citations
TL;DR: The work presented here builds on the IETF multi-protocol lambda switching (MPλS) initiative and addresses the implementation issues of the path selection component of the traffic-engineering problem in a hybrid IP-centric DWDM-based optical network.
Abstract: Recent advances in optical networking technologies are setting the foundation for the next-generation data-centric networking paradigm, an “Optical Internet”. This work addresses one of the most challenging issues facing today's service providers and data vendors; how will the SONET/SDH-based legacy infrastructure currently in place make a graceful transition to the next generation networking paradigm? A simplified, two-tiered architecture that requires two types of sub-systems will set the stage for a truly optical internet: service delivery platforms that enforce service policies; and transport platforms that intelligently deliver the necessary bandwidth to these service platforms. If IP can be mapped directly onto the WDM layer, some of the unnecessary network layers can be eliminated, opening up new possibilities for the potential of collapsing today's vertically layered network architecture into a horizontal model where all network elements work as peers to dynamically establish optical paths through the network. This paper presents a balanced view of the vision of the next-generation optical internet The work presented here builds on the IETF multi-protocol lambda switching (MPλS) initiative and addresses the implementation issues of the path selection component of the traffic-engineering problem in a hybrid IP-centric DWDM-based optical network. An overview of the methodologies and associated algorithms for dynamic lightpath computation is presented. Specifically, we show how the complex problem of real-time provisioning of optical channels can be simplified by using a simple dynamic constraint-based routing and wavelength assignment (RWA) algorithm that compute solutions to three sub-problems: (a) routing; (b) constrained-based shortest-route selection; (c) wavelength assignment. We present two different schemes for dynamic provisioning of the optical channels. The two schemes use the same dynamic lightpath computation approach proposed here, except that the third component, that is the wavelength assignment algorithm and its implementation, is different for each of the two schemes.
11 citations
TL;DR: This paper proposes a new architecture for building nonblocking optical switching networks that has much lower signal loss and crosstalk than the crossbar without increasing switch complexity.
Abstract: With the current technology, all-optical networks require nonblocking switch architectures for building optical cross-connects. The crossbar switch has been widely used for building an optical cross-connect due to its simple routing algorithm and short path setup time. It is known that the crossbar suffers from huge signal loss and crosstalk. The Clos network uses a crossbar as building block and reduces switch complexity, but it does not significantly reduce signal loss and crosstalk. Although the Spanke's network eliminates the crosstalk problem, it increases the number of switching elements required considerably (to 2N
2 - 2N). In this paper, we propose a new architecture for building nonblocking optical switching networks that has much lower signal loss and crosstalk than the crossbar without increasing switch complexity. Using this architecture we can build non-squared nonblocking networks that can be used as building block for the Clos network. The resulting Clos network will then have not only lower signal loss and crosstalk but also a lower switch complexity.
TL;DR: Four kinds of traffic grooming algorithms depending on the considered virtual topologies of WDM multi-ring networks according to the way in which traffic is transmitted among rings are designed: mixed (MTG), partially mixed (PMTG), separate (STG), and independent (ITG).
Abstract: In this paper, we propose novel traffic grooming algorithms to reduce the cost of the entire system in WDM multi-ring networks. In order to achieve this goal, it is important to construct a virtual topology and groom the traffic in these networks. We consider four kinds of virtual topologies of WDM multi-ring networks according to the way in which traffic is transmitted among rings. Accordingly, we design four kinds of traffic grooming (TG) algorithms depending on the considered virtual topologies: mixed (MTG), partially mixed (PMTG), separate (STG), and independent (ITG) traffic grooming algorithms. Each algorithm consists of a separation, a connection-ring construction, and a grooming procedure. In the separation procedure, all traffic connections are classified into intra and inter-connections. The connection-ring construction procedure makes full connection-rings from traffic connections. The grooming procedure groups connection-rings onto a wavelength in order to reduce the number of SONET add/drop multiplexers (SADMs) and wavelengths and to improve the utilization of network resources. To analyze the performance of each algorithm, a circular multi-ring architecture with uniform traffic is considered. The simulation results show that ITG and PMTG are more efficient in terms of wavelengths. STG and PMTG require a smaller number of SADMs.
TL;DR: Switch architectures to support dynamic wavelength encoding and the related performance evaluation are presented and discussed in the paper, evidencing the benefits of packet switching over WDM.
Abstract: Packet switching over wavelength division multiplexing (WDM) channels is considered with the aim to investigate algorithms for wavelength assignment and to define feasible switch architectures, in the presence of connectionless or connection-oriented transfer modes. In particular, as regards the connection-oriented scenario, mapping of virtual connections onto wavelengths operated by network nodes is considered and procedures are proposed to achieve statistical multiplexing efficiency by dynamic wavelength re-assignment. Switch architectures to support dynamic wavelength encoding and the related performance evaluation are presented and discussed in the paper, evidencing the benefits of packet switching over WDM.
TL;DR: This paper addresses a novel routing and switching method for optical IP networks — flow routing, and its facilitating protocol, and concludes that EFD behaves as a robust technique, which is more tolerant than FD to the change of traffic and transmission system factors.
Abstract: Optical packet-switching networks deploying buffering, wavelength conversion and multi-path routing have been extensively studied in recent years to provide high capacity transport for Internet traffic. However due to packet-based routing and switching, such a network could result in significant disorder and delay variation of packets when they are received by end users, thus increasing the burstiness of the Internet traffic and causing higher-layer protocol to malfunction. This paper addresses a novel routing and switching method for optical IP networks — flow routing, and its facilitating protocol. Flow routing deals with packet-flows to reduce flow corruption due to packet out-of-order, delay variation and packet loss, without using complicate control mechanism. Detailed performance analysis is given for output-buffered optical routers adopting flow routing. Two flow-oriented discarding techniques, i.e., flow discard (FD) and early flow discard (EFD), are discussed. Compared with optical packet-switching routers, a remarkable improvement of good-throughput is obtained in the optical flow-routers, especially under high congestion periods. We conclude that EFD behaves as a robust technique, which is more tolerant than FD to the change of traffic and transmission system factors.
TL;DR: This paper proposes labeling of the optical packets based on multidimensional headers constructed by using a combination of two or more physical properties like time, wavelength, sub-carried frequency, or polarization state, which offers potential speed processing gains over the binary case as well as improvements on bit-error rate versus OSNR.
Abstract: Bit-asynchronous optical packet-switched networks are seen as viable candidates for Metropolitan areas. For such networks we are proposing labeling of the optical packets based on multidimensional headers constructed by using a combination of two or more physical properties like time, wavelength, sub-carried frequency, or polarization state. The resulting header can be processed using slower electronics than the line rate without any sacrifice of the information transfer rate and with higher immunity with respect to degradation of the optical signal-to-noise ratio (OSNR). Packet identification as well as header-payload separation is achieved using passive devices. This method for constructing and switching information as well as transporting frames offers potential speed processing gains over the binary case as well as improvements on bit-error rate versus OSNR. The feasibility of using headers constructed by combination of wavelength and in terms of dispersion and spectral efficiency is established as a function of bit-rate and distance. Finally a generic architecture for a suitable optical packet add/drop node is described.
TL;DR: The enhancements obtained by augmenting traditional MSN (Manhattan Street Networks) with optical buffering with impact of the parameters associated with optical buttering, such as the number of delay loops and the loop length, are discussed in detail.
Abstract: Multihop networks are strong candidates for the implementation of high-speed networks, ranging from back-plane networks for cluster computing to metropolitan-area networks. Besides using deflection routing for contention resolution, optical buffering may be used to enhance the performance of optical multihop networks and to reduce or even eliminate the need for optical-electrical conversions. The enhancements obtained by augmenting traditional MSN (Manhattan Street Networks) with optical buffering are evaluated. The MSN considered here is based on a novel 6 × 6 optical switching node with up to two fiber delay loops. Impact of the parameters associated with optical buttering, such as the number of delay loops and the loop length, are discussed in detail.
TL;DR: The functional elements of the protocol are described and the way they interact to support the Diffserv's Expedited Forwarding PHB and Assured Forwarding (AF) PHB group is described, where PHB stands for Per-Hop-Behavior.
Abstract: This paper presents a Media Access Control (MAC) protocol for a WDM passive optical star. The protocol supports scalable service differentiation for Internet traffic in the spirit of the IETF's Diffserv architecture. We describe the functional elements of the protocol (signaling, arbitration, service disciplines and buffer management techniques) and the way they interact to support the Diffserv's Expedited Forwarding (EF) PHB and Assured Forwarding (AF) PHB group, where PHB stands for Per-Hop-Behavior. Extensive simulation results give quantitative estimations of the performance of the protocol under combined EF/AF traffic.
TL;DR: By the use of both, high-speed electronics for implementing functions of higher complexity with higher level of parallelism and all-optical techniques for the realization of simple ultra fast medium access functions, a hybrid medium access node capable of handling high data rates can be designed.
Abstract: In this paper, photonic technologies for the realization of high-capacity optical time-division multiplexed (OTDM) local and metropolitan area networks (LANs and MANs) are addressed including all-optical techniques such as ultra short pulse generation, all-optical clock recovery, optical multiplexing/demultiplexing, and optical packet compression/decompression Furthermore, the new trends in high-speed electronics, data processing and optical interconnects are analyzed enabling the avoidance of the electronic processing bottleneck By the use of both, high-speed electronics for implementing functions of higher complexity with higher level of parallelism and all-optical techniques for the realization of simple ultra fast (> 40 Gbit/s) medium access functions, a hybrid medium access node capable of handling high data rates can be designed
TL;DR: A new model, which contains innovative elements, is provided, and it is shown that the innovative network structure, i.e., use of a passive wavelength router node (PWRN), works also perfectly with more different traffic streams.
Abstract: The “switchless” all-optical network aims to provide a future single-layer, advanced transport architecture on a national scale. The single-hop, shared-access network employs time and wavelength agility (a WDMA/TDMA scheme), using fast tuneable transmitters and receivers, to set up individual customer connections through a single wavelength router, which is suitably replicated for resilience. While in a recent paper we reported the analysis and dimensioning of a switchless network assuming just the telephone traffic, we provide in this paper a new model, which contains innovative elements, and report original results assuming to deal with data traffic of two different types: constant bit rate (CBR) and variable bit rate (VBR). The innovation is based on the fact that the model considers more traffic flows with different traffic requirements (e.g., bandwidth, duration) as input to a group of time-slot connections on the same wavelength between two passive optical networks (PONs). We obtained analytical expressions of the main traffic characteristics (loss probability, throughput and overflowing traffic) both for the primary group of time-slots and for the secondary group of time-slots, to which the overflowing traffic streams enters. Moreover, we show that the innovative network structure, i.e., use of a passive wavelength router node (PWRN), works also perfectly with more different traffic streams. The analytical model presented in this paper has been compared with a simulation model. The comparison has revealed very good agreement. Relevant network cases are considered, and the dimensioning of the network in such cases is reported, in terms of the key network parameters, loss probability and throughput.
TL;DR: A taxonomy of OADMs is given to serve as a frame work for cost and performance studies on dense wavelength division multiplexing (DWDM) optical transmission systems.
Abstract: The use of optical add/drop multiplexers (OADMs) is considered as a possible way to save the number of transponders required at a network node by optically bypassing wavelengths that do not need to be dropped. There are many different flavors of OADMs offered by vendors. In this paper, we give a taxonomy of OADMs from the perspectives of both technology considerations and possible implications on network performance. The purpose of the taxonomy is to serve as a frame work for cost and performance studies on dense wavelength division multiplexing (DWDM) optical transmission systems.
TL;DR: The proposed modular and scalable all-optical packet switch architecture is feasible to be implemented, and can be a good candidate for future packet switching solutions.
Abstract: In this paper, a modular and scalable all-optical packet switch (AOPS) is proposed. The range of its capacity can be easily scaled from gigabit per second to multi-terabits per second. Due to its broadcast-and-select property, the proposed AOPS is capable of performing a multicast function. By taking the advantage of wavelength division multiplexing (WDM), this architecture can provide the best network performance using a limited number of optical fiber delay lines as buffers. To perform the header replacement function, a novel all-optical header replacement unit (HRU) is introduced to be integrated with the switching function. The proposed HRU is shared by all the inputs which provides cost advantages. In addition, we present a generic control scheme for the proposed AOPS. To implement the function of the AOPS, two possible approaches, based on the design of wavelength conversion pools (WCPs), are presented and their cascadability performances are compared. Our simulations show that the proposed AOPS with an arrayed waveguide grating (AWG) based WCP provides better cascadability performance than the one with a star coupler based WCP. We conclude that, based on the status of current optical and electronic technologies, the proposed architecture is feasible to be implemented, and can be a good candidate for future packet switching solutions.
TL;DR: In this paper, a dynamically configurable DWDM transmission technology for bit rates up to 10 Gb/s has been investigated in a field trial in Berlin, which is part of the KomNet research project.
Abstract: Dense wavelength division multiplexing (DWDM) is the key technology for future data transport It combines transmission of data rates up to several Tb/s [1] with an overall transparency to data format and bit rate The expected huge bandwidth demand in the near future requires an adaptability of DWDM transmission technology to metropolitan networks Therefore, dynamically configurable DWDM transmission technology for bit rates up to 10 Gb/s has been investigated in a field trial in Berlin This field trial is part of the KomNet research project It is the goal of this field trial to optimize DWDM systems to metropolitan network requirements Several aspects are in this paper: (i) A network simulation tool is described which helps to enlighten the profitability of statically and dynamically configured network nodes (ii) A newly developed technology to add and drop single-wavelength channels is explained (iii) The scalability of the approach is demonstrated with an aggregate capacity of 08 Tb/s The equipment has already been installed in the field and is ready for experiments
TL;DR: Three architectures, namely Gigabit Ethernet, Packet over Sonet/ SDH and Dynamic Packet Transport are investigated and evaluated as an alternative to the IP/ATM/SDH/WDM architecture.
Abstract: The commonly used IP-backbone network architecture of today is IP/ATM/SDH/WDM This architecture has many redundant functionalities and is not optimized to transport IP traffic New approaches for simplified network architectures try to eliminate redundant functionalities and to decrease the protocol overhead and thereby transport IP as efficiently as possible over WDM-based optical networks EURESCOM project P918 “Integration of IP-over-optical networks: networking and management” investigated scenarios for optimized IP transport in WDM-based backbone networks In this paper, three architectures, namely Gigabit Ethernet, Packet over Sonet/SDH and Dynamic Packet Transport are investigated and evaluated as an alternative to the IP/ATM/SDH/WDM architecture
TL;DR: The ability of electronically tuned lasers to cope with demanding channel spacing and inevitable low frequency setting error is demonstrated and new possibilities for DWDM access networks are opened up.
Abstract: As WDM channel spacing continues to decrease in size, and with the application of tunable lasers in DWDM (dense wavelength division multiplexing) systems, we demonstrate the ability of electronically tuned lasers to cope with demanding channel spacing and inevitable low frequency setting error. By finding the stable operating points of a single tunable laser at the desired frequencies, using advanced software for feature extraction a look-up table to drive the laser was generated. Once the drive currents to access 2000 channels in a 2 GHz comb are found, and in order to justify their usability in WDM networks, their frequency setting error and Side Mode Suppression Ratio (SMSR) was found. These results open up new possibilities for DWDM access networks while pointing to new potential for management of versatile wavelength re-allocation as well as providing a limit of achievement for channel density and granularity in the optical fiber network.
TL;DR: It is shown that by some modifications in the basic AR/LTP local area protocol and by parallel processing of connection requests, commands and control signals, the waiting time performance of a Robust-WDM interconnection can be improved.
Abstract: Robust-WDM is a technique to realize wavelength division multiplexed (WDM) local area networks (LANs) in the presence of laser wavelength drifts. Various medium access control (MAC) protocols have been proposed for Robust-WDM LANs. Among these protocols, the one with Aperiodic Reservation and Lenient Token-Passing control channel (the AR/LTP protocol) is the most promising. We discuss three internetworking strategies for AR/LTP Robust-WDM LANs. The aim is to explore the possibility to scale the AR/LTP Robust-WDM concepts to the metropolitan domain by looking at some basic medium-access arrangements and specifying the advantages and limitations of each. Special Remote Access Nodes (RANs) are proposed to facilitate interconnection. It is shown that by some modifications in the basic AR/LTP local area protocol and by parallel processing of connection requests, commands and control signals, the waiting time performance of a Robust-WDM interconnection can be improved. The improvement would be accomplished at the expense of some control sophistication. Further improvement can be achieved by designing a set of point-to-point links among the RANs of different Robust-WDM stars. In this case, control is relatively simplified, but the design of a RAN is made more complex and expensive.
TL;DR: It is found that in metropolitan areas the scalability of a WDM-ring network using bidirectional transmission is not mainly limited by the RIN arising from the Rayleigh backscattering.
Abstract: We analyze the scalability of a metropolitan bidirectional multifiber wavelength-division-multiplexed (WDM) ring network. The analysis is carried out by using a bidirectional transmission model for optical networks and by building an experimental network. The model includes major limiting factors in WDM-ring networks such as relative intensity noise (RIN) due to multiple Rayleigh backscattering, amplified spontaneous emission (ASE) accumulation in a cascade of bidirectional erbium-doped fiber amplifiers (EDFA), tilting of the EDFA gain spectrum and input saturation power of the EDFA. We found that in metropolitan areas the scalability of a WDM-ring network using bidirectional transmission is not mainly limited by the RIN arising from the Rayleigh backscattering. The result was verified experimentally. The maximum size of the demonstrated network is 33–43 nodes with a spacing of 5–10 km between nodes. With this spacing, which is typical in metropolitan areas, the scalability of the network is mainly limited by the gain tilt and the input saturation power of the EDFA.
TL;DR: This paper analyzes wavelength division multiplexing technology, in both high capacity links and optical networks, highlighting the impact of fiber non-linearity, and addressing the main source of impairments.
Abstract: The rapidly increasing data traffic volumes will demand for very high transmission capacity and network nodes’ throughput. Wavelength division multiplexing (WDM) technology will be asked to support many channels on the same fiber, both in point-to-point links and in WDM optical networks. The transmission of a high number of wavelength channels in all these systems is a key issue. This paper analyzes this topic, in both high capacity links and optical networks, highlighting the impact of fiber non-linearity, and addressing the main source of impairments. This is done through the use of a semi-analytical model recently upgraded to account for all the contributions deriving from Kerr effects, particularly four-wave mixing and cross-phase modulation. The analysis reveals that more than one hundred of channels at 2.5 Gbit/s can be transmitted in point-to-point links whose length can span until the order of 1000 km, and 32 channels per fiber, at the previous bit rate, can be handled in WDM networks, without dispersion compensation. For a higher number of channels (e.g., 64) dispersion compensation is needed.
TL;DR: A new receiver architecture using multi-wavelength selectivity to eliminate the penalties, and a corresponding optimal scheduling algorithm for uniform all-to-all transmission is proposed, which results in significant cost reduction in comparison with existing pipeline technique.
Abstract: The use of low-speed tunable devices in packet-switched WDM star networks may lead to throughput and delay penalties. We propose (i) a new receiver architecture using multi-wavelength selectivity to eliminate the penalties, and (ii) a corresponding optimal scheduling algorithm for uniform all-to-all transmission. This architecture results in significant cost reduction in comparison with existing pipeline technique. When using a two-wavelength simultaneous selection, our numerical results show that (i) the throughput can increase by 40% in comparison with using a tunable filter alone; (ii) the throughput degradation is 2% in comparison with using two tunable filters in systems using a pipeline technique.
TL;DR: An efficient optical packet addressing technique for optical packet-switched networks, where the pre-assigned RF frequency carriers are used to represent the packet addresses, can simplify the control process of optical packet switching.
Abstract: We propose an efficient optical packet addressing technique for optical packet-switched networks, where the pre-assigned RF frequency carriers are used to represent the packet addresses. It can simplify the control process of optical packet switching so that it results in reduced address processing time and smaller complexity of the packet address processor due to simple extraction of address information. We also analyze the performance of the proposed packet addressing scheme in the transmission aspect taking into account packet address wavelength beating and laser nonlinearity.
TL;DR: A network based on an array waveguided multiplexer and arrays of non-tuneable or slow tuneable transmitters and receivers and an uniformly distributed traffic matrix is suggested in order to avoid the costs of the fast tuneable devices.
Abstract: Some of today's optical networks are based on the well known WDM-star topology. In most cases, these are single-hop networks equipped with fast-tuneable wavelength transceivers. For these well studied packet-switched networks, several protocols have been designed. In order to avoid the costs of the fast tuneable devices, a network based on an array waveguided multiplexer (AWGM) and arrays of non-tuneable or slow tuneable transmitters and receivers is suggested. In order to enable communication among all stations, a multi-hop environment is introduced which is determined by the AWGM routing matrix. In the case of slow-tuneable devices, the topology can be reconfigured in dependence on changing traffic patterns. In order to get a first insight into the performance of these topologies, we focus on the case of fixed transceiver units and an uniformly distributed traffic matrix.