Optical Label Switching Networks Research Articles

A Joint Multicast Optimization Approach for QoS Provisioning in Optical Label Switching (OLS) Networks

Abstract Optical label switching is introduced for ensuring fast data transfer, quality of service (QoS) support, and better resource management. However, the important issue is how to optimize resource usage and satisfy traffic constraints for improving network performance and design. This paper proposes a dynamic approach that optimizes the resource in terms of link capacity and FDL (fiber delay line) buffering as well as a wavelength converter. The proposed approach decreases the resources usage and guarantees QoS support for various traffic demands. The optimization strategy consists of two stages: path building and traffic management. The path building assures logical topology making using the cumulative cost of available resource and traffic requirements including unicast and multicast. The traffic management solves the resource formulation problem during the traffic transfer by guaranteeing the required loss and blocking delay. Simulation work is conducted for validating the proposed approach and evaluating its performances and effectiveness. Simulation results show that our proposal minimizes effectively the use of link capacity of lightpath and light-tree. Moreover, our approach optimizes the use of buffering capacity and wavelength converter and guarantees QoS support according to traffic requirements.

A Novel Multicast Scheme with Grooming for Quality of Service (QoS) Provision and Resource Optimization over Optical Label Switching (OLS) Networks

Abstract Optical label switching is proposed for providing fast all-optical switching, covering all granularities transfer and assuring quality of service support. However, the important issue is improving optical resource and providing a steadiness between satisfying traffic demands and reducing resource utilization. This paper proposes a novel multicast approach which enables grooming using an upgraded core node architecture that switches suitably unicast and multicast connections. The proposed node architecture manages appropriately all optical resource including a fiber delay line and wavelength bandwidth, as well as traffic requirements. A new label framework is introduced to assure the required information exchange for handling suitably real-time traffic constraints and optical resource status. Moreover, innovative signaling and switching schemes are introduced to perform suitably lightpath and traffic constraints supervision. Theoretical model and simulation experiments are conducted for validating the proposed scheme and evaluating its performances and effectiveness. Finally, the proposal guarantees traffic requirements and reduces resource usage while improving resource availability.

Flexible-rate optical packet generation/detection and label swapping for optical label switching networks

Abstract In recent years, optical label switching (OLS) gains lots of attentions due to its intrinsic advantages to implement protocol, bit-rate, granularity and data format transparency packet switching. In this paper, we propose a novel scheme to realize flexible-rate optical packet switching for OLS networks. At the transmitter node, flexible-rate packet is generated by parallel modulating different combinations of optical carriers generated from the optical multi-carrier generator (OMCG), among which the low-speed optical label occupies one carrier. At the switching node, label is extracted and re-generated in label processing unit (LPU). The payloads are switched based on routing information and new label is added after switching. At the receiver node, another OMCG serves as local oscillators (LOs) for optical payloads coherent detection. The proposed scheme offers good flexibility for dynamic optical packet switching by adjusting the payload bandwidth and could also effectively reduce the number of lasers, modulators and receivers for packet generation/detection. We present proof-of-concept demonstrations of flexible-rate packet generation/detection and label swapping in 12.5 GHz grid. The influence of crosstalk for cascaded label swapping is also investigated.

Simple Scheme for PDM-QPSK Payload Generation in an Optical Label Switching Network

We propose and experimentally demonstrate a novel and simple scheme for dual-polarization vector pay-load generation in an optical label switching network. The 8 Gbaud quadrature-phase-shift-keying (QPSK) payload, generated by one intensity modulator with signal precoding and optical carrier suppression, is first polarization-multiplexed by a polarization multiplexer, then combined with a 2.5 Gb/s label before being transmitted over 20 km single-mode fiber, and finally separated from the label and recovered by the receiver with less than 2 dB power penalty. The proposed scheme can facilitate label insertion and is suitable for an optical label switching network with a simple architecture.

Using Stuffed Quadratic Congruence Codes for SAC Labels in Optical Packet Switching Network

While optical codes in optical code-division multiple access (OCDMA) has been extensively investigated, research of optical coding labels in optical multi-protocol label switching (MPLS) network is relatively unexplored. This paper studies optical labels with spectral-amplitude coding (SAC) for optical packet switching (OPS) network. The research focuses on implementing two different codes in optical labels: stuffed quadratic congruence (SQC) codes and M-sequence codes. Label-error rate (LER) is quantified to ascertain the influence of code pattern on system performance. The findings suggest that SQC coded label can support more numbers for label stacking, due to its very low cross-correlation value.

Traffic Grooming and QoS Management over OLS Networks

Optical label switching (OLS) has been proposed as promising technology for providing seamless integration of data transmission and optical networking while supporting data burst and packet handling using label paradig m. The current status of OLS technology can insure fast switching, contention resolution and QoS provision. The main issue in OLS networks is how to improve network efficiency according to traffics requirements, since resources managing and traffic trans mission are fundamental criteria that can influence the networking platform design. Imp roving network efficiency in OLS networks can be achieved using grooming traffic along transmission path or Label Switching Path (LSP) for providing a balance between resources allocation and utilizat ion. In this paper, we proposed a real-t ime traffic groo ming scheme through the use of an upgraded OLS core node architecture that can efficiently integrate several input traffics on the unique output port. The proposed scheme tries to increase the usage of the available resources in terms of Optical Delay Line (ODL) and wavelength conversion. This scheme introduces a new label switching framework that transports the requested information for handling suitably the grooming procedure, especially traffic requirements and real-time reachable resources. In addit ion, the p roposed scheme perfo rms a set of advanced functions including signaling tasks, resources allocation and utilizat ion mechanisms as well as dynamic QoS management. Finally, theoretical model and simu lation work will be conducted in order to validate our proposal and evaluate its performances and effectiveness.

Virtual Optical Buffers: A Novel Interpretation of OCDMA in Packet Switch Networks

Among all proposed structures for optical networks, the optical packet switching (OPS) scheme, due to its practical implementation of IPs in an optical configuration and the consequent advantages, is a prizeworthy candidate for being employed in metropolitan area network and local area network communication levels. One of the few problems frequently met using the OPS structure in the fiber-optics realm is the lack of optical buffers, thus deteriorating the system's flexibility and quality of service. For example, optical label switching networks that have been developed recently based on the generalized multiprotocol label switching protocol, profoundly suffer from this setback which is considered as a great hurdle in their evolution. In this paper, we first introduce the input and output buffer switching models while deducing their blocking probability formulations. Then, by utilizing codes in the OPS structure, we closely examine the potential of code and/or wavelength switching in packet switching networks and also determine their blocking probability. Due to close similarities between different scenarios, we present the prospect of virtual optical buffers using codes, which have close performance to input and output buffers in sight of block probability. The most significant distinction in using virtual buffers is the fact that due to their substantial nature, they happen to exhibit some error probability. However, on account of the advantageous features of codes, the simulated and formulated error probability for both coherent and noncoherent optical code division multiple access (OCDMA), such as Spectrally phase encoded OCDMA and optical orthogonal codes, using virtual buffers, tends to be negligible. Two main code and wavelength switching schemes are also brought to attention in this work, the intelligent and random methods. These scenarios demonstrate an even greater behavioral performance to that of the mere code switching scenario, leading into a more reliable adaptation of virtual buffers. In addition, simulations results happen to provide clear verifications to our analytical approach.

A novel orthogonal modulation format of D8PSK/ASK with differential bi-phase encoding and its application in a label switching optical network

The principle of a novel orthogonal modulation format of differential 8-level phase-shift keying amplitude-shift keying (D8PSK/ASK) with differential bi-phase encoding (DBC) is introduced. Based on it, an optical labeling scheme, in which the payload is 100 Gbit/s D8PSK signal and the label is 10 Gbit/s DBC-ASK signal, is proposed and simulated. The results are compared with other current schemes, and the effects of transmission range, modulation extinction ratio (ER) and received power on system performance are analyzed, respectively. The results show that the spectrum efficiency and bit error rate (BER) are improved greatly, and when the modulation ER is increased to 11 dB, the balanced performance between the payload and label is achieved.

An Overview of Optical Label Switching Technology

Optical label switching is a new technology of optical switching, which can overcome the electronic bottleneck of optical communication effectively, optical label switching (OLS) network as a specific implementation of future optical packet network has been paid more and more attention, its key technology is the generation and extraction of optical label. In this paper, subcarrier multiplexing label, OCDM optical code label and orthogonal modulation label are described and discussed. Their strength and weakness are analyzed.

155 Mb/s–10 Gb/s combined FSK-IM/optical label-packet modulation signals 100 km transmission over standard single mode fiber using mid-span spectral inversion by four-wave mixing in an SOA

This paper introduces the mid-span spectral inversion by four-wave mixing in a commercially available semiconductor optical amplifier (SOA) with a length of about 1.5 mm to optical label switching network based on combined frequency shift keying (FSK)-intensiy modulation (IM)/optical label-packet modulation to overcome the dispersion limitation of fiber. The 155 Mb/s–10 Gb/s combined FSK/IM signal is experimentally transmitted over a 100 km standard single mode fiber. 10−10 and 10−9 BER (bit error ratio), or even better, is achieved for the FSK label and IM packet, respectively. The –19 dB power conversion efficiency is obtained for –1 nm wavelength detuning.

Optical Phase Add–Drop for Format Conversion Between DQPSK and DPSK and its Application in Optical Label Switching Systems

We propose and experimentally demonstrate an optical phase ldquoadd-droprdquo scheme to enable the format conversion between a 20-Gb/s differential quadrature phase-shift keying (DQPSK) and 10-Gb/s differential phase-shift keying. Meanwhile, the incoming DQPSK could be directly forwarded to another wavelength through the proposed optical phase ldquodroprdquo scheme, which is implemented by four-wave-mixing effect in highly nonlinear fiber. By orthogonally encoding the label and payload of the optical packet on the in-phase ( I) and quadrature ( Q) components of DQPSK, the proposed scheme could be applied in the optical label switching networks. The label erasing and rewriting of optical packets can be achieved through the proposed optical phase ldquodroprdquo and ldquoaddrdquo schemes, respectively.

Investigation of high-speed optical FSK generation scheme based on carrier suppression and phase modulation

We propose and numerically investigate a novel high-speed (40-Gb/s and above) optical frequency shift-keying (FSK) transmitter scheme. By optical carrier-suppressed modulation and differential phase-shift-keying (DPSK) to intensity modulation (IM) conversion, only one light source is needed in the proposed scheme to generate high-speed optical FSK signals. By using a Mach–Zehnder modulator (MZM) as phase modulator and an additional delay interferometer (DI) cascaded after the carrier-suppressed MZM to suppress the remaining carrier, the performance of our scheme can compete with the double-light-source counterparts. The transmission performances of the FSK signal generated with the proposed scheme as well as detuning and bandwidth tolerance of the demodulation filter are also carefully investigated. Simulation results show that the proposed FSK generation scheme is very suitable for the next-generation optical access network and optical label switching network. A potential application of our scheme in high-speed passive optical network is proposed.

Performance analysis of a dynamic QoS scheme in optical label-switched networks

In order to support the fast growing demand for transmission capacity, Optical Label Switching technology (OLS) seems to be a strong candidate because it allows fast switching capability and Quality of Service (QoS) support. One of the main aspects in OLS networks is the development of a QoS scheme that can efficiently handle QoS provision and resource utilization. OLS technology was made to support a static QoS model in which the service differentiation is defined based on the concept of priority. In this paper, we propose a novel QoS model using dynamic performance parameters. Our approach provides dynamic per-hop information of each traffic type in OLS core using two parameters: loss and delay, and redefines the fundamental functionality of an OLS core node including: an enhanced signaling, which handles lightpath establishment, and a novel contention resolution. A theoretical model is developed for evaluating the performance of the proposed model by means of a conservation law and a queuing network model. Finally, the performance of the proposed model is analyzed using simulation.

Optical labeling using carrier suppressed second harmonic subcarrier label

AbstractA carrier‐suppressed second harmonic subcarrier‐multiplexed labeling technique for optical label switching network is demonstrated. It provides frequency doubling for optical subcarrier label so that requirement for high bandwidth optical or electrical components can be reduced. The results of two‐span transmission of 10‐Gb/s payload with 1.244‐Gb/s subcarrier label show improved performance of the labeling technique. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1468–1470, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22418

Transmission performance of the SCM label in optical label switching networks

We have investigated the transmission performance of the label signal in the optical double sideband subcarrier multiplexing (DSB-SCM) label switching link and clarified that the degradation of the label signal results from the fiber chromatic dispersion and the incomplete filtering out of the payload carrier. Our theoretical results show that the DSB-SCM label can immune the fading effect, and the degradation mainly results from the crosstalk from the payload and the time shift of the code edge. The deep suppression of the optical carriers at the receiver can eliminate the crosstalk. The time shift of the code edges leads to the eye closure of the label codes and is independent of the code rate, but it does not degrade the label code with a low bit rate greatly, although it is serious for the label with a high bit rate and ultimately limits the transmission distance of the label. The simulation results validate our analysis very well. As we theoretically predict that the single sideband (SSB)-SCM can eliminate the time shift of the code edges and extend the transmission distance of the label signal.

All-Optical Label Swapping, Clock Recovery, and 3R Regeneration in 101-Hop Cascaded Optical-Label Switching Router Networks

This paper experimentally demonstrates the cascaded operation of an optical-label switching router for up to 101 hops, with optical label swapping, optical clock recovery, and 3R regeneration (re-amplification, reshaping, and retiming) at each hop. The optical label swapping utilizes all-optical payload/label separation and label rewriting with subcarrier label. An interferometer wavelength converter enables the reshaping function, while the synchronous modulation driven by the optically recovered packet clock performs the retiming function. The optical label swapping and 3R regeneration enable the packets to traverse a large number of hops while maintaining the signal quality to support the scalability of the optical-label switching network

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

A novel scheme for generating optical dark return-to-zero pulses and its application in a label switching optical network

We experimentally demonstrate a novel and simple method to generate a dark return-to-zero (RZ) pulse with tunable pulsewidth and extinction ratio by using a dual-arm LiNbO /sub 3/ intensity modulator. Our experimental results show that this dark RZ pulse signal can be used in a 10-Gb/s optical packet switching system as an optical label. In addition, we demonstrate that this dark RZ label can be easily erased using the gain saturation effect in a semiconductor optical amplifier.

Demonstration of all-photonic spectral label-switching for optical MPLS networks

All-photonic label-switching of weight four spectral packet labels (concurrent quadruple wavelength conversion) is demonstrated for optical multiprotocol label-switching networks. The experimental setup is based on cross-gain modulation in a fiber ring laser using a semiconductor optical amplifier gain medium and uses commercially available components. Static transfer functions and step response measurements for various input-output label-switching combinations show that a noisy input label with small extinction ratio can be switched to a clean, amplified, output label

Label erasure using an imbalanced NOLM and its application in a 40-gb/s label switching optical network

A novel scheme based on the nonlinear transmission function of an imbalanced nonlinear optical loop mirror (NOLM) is used to realize label erasure. The scheme has been successfully applied in a 40 Gb/s label switching optical network with a transmission distance of 200 km.