This paper focuses on the problem of optical buffer control strategies for recirculation shared optical buffer in optical packet switching. Five control algorithms are presented, and their performances are evaluated and compared by computer simulations. Issues on the optimal configuration of optical buffers are also discussed. The numerical results show that the time delay resolution of fiber delay line has significant influence on the system performance in all three discussed switching mode. The results are valuable in designing the optical packet switch.
In this paper, we investigate the somewhat untraditional approach of contention resolution in WDM optical packet switches. The most striking characteristics of the developed switch architecture are that (1) contention resolution is achieved by a combined sharing of fiber delay-lines (FDLs) and tunable optical wavelength converters (TOWCs); (2) FDLs used for contention resolution is in non-degenerate form, i.e., buffers are achieved by non-uniform distribution of the delay lines; (3) TOWCs just can achieve wavelength conversion in partial continuous wavelength channels, i.e., sparse wavelength conversion. We describe and analyze the concrete configuration of FDLs and TOWCs under non-bursty and bursty traffic scenarios. Simulation results demonstrate that for a prefixed packet loss probability constraint, e.g., 10-6, the developed architecture provides a different point of view in the optical packet switching (OPS) design. That is, combined sharing of FDLs and TOWCs can, effectively, obtain a good tradeoff between the switch size and the cost, and TOWCs which are achieved in sparse form can also decrease the implementing complexity.
This paper investigates the implementing techniques concerning 2-to-1 node receiver for all-optical packet switching. We point out that the state-of-the-art technologies introduced in the literatures are all associated with one main limitation, i.e., even if two incoming packets are directed to the different ports and thus no contention will occur, they can not be directed to the output ports simultaneously. To overcome this problem, a novel node receiver model is proposed in this paper. This work presents a solution that makes use of fiber delay-lines (FDLs) which allow multiple packets to be concurrently stored or transmitted. With a novel switch control, it is shown that this solution is very efficient to resolve contention, and overcomes the limitation existing in the current models (e.g., Quadro, M-Quadro and COD architectures). We describe and analyze the concrete scheduling of the switches. Simulation results based on bursty and non-bursty traffic scenarios demonstrate that the proposed node architecture (1) performs well in terms of performance metrics such as packet loss probability; (2) has a simple control requirement. In addition, we find that the required number of the recirculating time of the packets is minimal.
Since optical ring is the main topology in metro ring, it is essential to study on the medium access control protocol. In this paper, medium access control protocols in metro optical ring are discussed. We firstly classify the current protocols, then analyze performance requirements and technology attributes thoroughly. At last, several topics remained to be studied are presented.
A novel, simple and controllable bandwidth allocation scheme, called bandwidth on Demand (BoD), is proposed for optical burst-switched network in this paper. It assures every service class to consume bandwidth no more than its granted percentage by examining the bandwidth usage of each class periodically. The burst loss ratios under arbitrary input loads are theoretically analyzed as well as numerically simulated. The theoretical descriptions accord with the simulated results very well. The scheme can be used as an effective scheme of bandwidth allocation and management.
In this paper, inefficiencies of the QoS scheme based on extra-offset-time-based priority for variable-length optical burst-switched network were pointed out, and a novel fixed-length burst assembly scheme is proposed. This scheme is not only practical, but also able to decrease the latency of bursts at the edge nodes. Compared to variable-length (traditional) scheme, a smaller blocking probability for the highest priority service and almost one third offset time delay for every class were obtained in fixed-length scheme.
Since Resilient Packet Ring has been the subject of intense research, it is necessary to study and analyze the performance of technology. In this paper, based on queuing theory and M/G/1/K queuing system, the average packet transfer delay following Darwin preliminary draft is analyzed. The results show that high priority traffic gets the lowest delay and the difference between medium and low priority traffic is small. In addition, the larger the network, the less is the difference. Maximum network throughput is also obtained in theory, which is instructive to further promote the related standard and even to design network in practice.
In order to improve the processing ability in the switching node, a lot of optical packet switching schemes were proposed, one of them is multi-wavelength label switching. In the scheme, a case of using K bit-long label and W different wavelengths can obtain WK unique labels at most. Here A novel label-coding scheme was put forward, which can produce more labels than before, For an example, if using 2 bit-long label and 2 different wavelengths, we can get 9 different labels, instead of 4 different labels using the old coding method proposed in the paper. At last, we give the design of the transceiver in detail.
This article focuses on the problem of switch control strategy for optical burst switch with optical buffer supporting variable length packets and under asynchronous mode. Two novel control algorithms are proposed, and their performances as well as that of the well-known reserve-switching mode, are evaluated and compared by computer simulations. Issues on the optimal configuration of optical buffers are also discussed. The numerical results show that the time delay resolution of fiber delay line has significant influence on the system performance in all three switching modes.
Optical Label Switching (OLS) is one of the practical manners of optical packet switching. It is a main research domain in optical networks. The advantage of OLS is its bandwidth efficiency and ability to support various network devices. There are a lot of practical problems need to be resolved. Today, research into OLS technology has focused on key networking and hardware issues such as high-speed optical switch, optical storage component, and network nodes source distribution optimization algorithm. The optical Label Header contains header synchronizing bits, routing address bits, etc. Header reading and rewriting includes synchronizing, routing and checking technologies. So it is the key issue in the OLS, and has very important research and application values. In this paper, a novel proposed fabric scheme was discussed to achieve the function of the header reading and rewriting. It can be applied to the high-speed header reading and rewriting to satisfy the requirements of practical applications. The fabric scheme adopts a high-speed tunable laser and wavelength converter to rewrite the header. The high-speed tunable laser is based on Grated Coupler Sampled Reflector (GCSR) structure and the wavelength converter is based on Cross-Phase Modulation (XPM) in a Semiconductor Optical Amplifier (SOA) and a Mach-Zehnder Interferometer (MZI) structure. The synchronization of the packet in the node also be discussed.
Wavelength-division multiplexing appears to be the solution of choice for providing a faster networking infrastructure that can meet the explosive growth of the Internet. Future networks are expected to utilize the WDM technology for optical functionalities capable of handling multi-Teragabit signals and thus the cost, therefore it is very important that the Optical cross-connects (OXCs) and optical Add-drop Multiplexers (OADMs) have performed routing and switching capacities. Optical Packet Switch (OPS) technology allows us to rapidly deliver the enormous network bandwidth. OPS offers high-speed data rate and format transparency. But there are still many technologies and key components need to solve. In this paper we propose a novel architecture for OPS using Tunable Wavelength Converters (TWC) and Fiber Delay-Lines (FDLs). We use wavelength converters and demuxes connected with several FDLs that provide different delay periods. Input wavelengths can be tuned to different ones in order to acquire different delay periods. Wavelength converters are shown to improve the traffic performance of the switch blocks for both random and burst traffic. It can also provide contention resolution solution in wavelength and time domains. This architecture improves packet switching speed and significantly decreases the use of optical switches comparing with general architecture. Finally, the simulation results show that the packet blocking can be decreased.
The realization technology of a new kind of multi-wavelengths label optical packet switching technology is discussed. In this switching, optical header is labeled by several optical pulses at different wavelengths in the same optical communication channel band as optical payload. The optical transmitter with header generation and packet formation, receiver with data restoration and switching node with route processing are introduced. The switching principle is verified by a simplified experiment.
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.
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.
Several tunable optical splitter techniques and some of their applications, including some prospective schemes, are discussed in this paper. It is explained by specific examples that all the variable transmission/reflection film technology, variable fiber couple length technology, acousto-optic/electro-optic deflection technology, and Mach-Zehnder interference technology are the capable technologies to realize tunable optical splitter, and tunable splitter technology to be applied to optical transmission networks, other devices and optical measurements.