Optical Label Switching Research Articles

Line-coded payload with PolSK label overlay in optical label switching

Optical label switching (OLS) is an attractive solution for the packet-based optical switching. A novel OLS method applying spectrum shaping line-coding (SSLC) is proposed in this paper. The label signal is superimposed on the amplitude shift keying (ASK) payload signal by polarization shift keying (PolSK) modulation. The low-frequency component of the payload signal is suppressed by line-coding to reduce the induced crosstalk to the label signal. The payload signal and the label signal could be received separately and directly by an ASK receiver and a PolSK receiver, respectively. The performance of the proposed scheme is tested by simulation. Several line-codes are proposed and compared in the simulation. The results of the simulation test show the feasibility of the proposal. Compared with previous OLS methods, the proposed method increases the code efficiency of the payload signal (from 50% to 75% and 80%) without reducing its extinction ratio (ER). So its effective bit rate is increased while its quality is not sacrificed.

A novel code shift keying for label superimposing in optical label switching

Optical label switching (OLS) is an attractive solution for the packet-based optical switching. A novel modulation method, i. e., code shift keying (CSK) is proposed for label modulation in this paper. The payload signal applies differential phase shift keying (DPSK) in Manchester code or NRZ format when the label data is “1” or “0”, respectively. The payload signal is detected by a Mach-Zehnder delay interferometer (MZDI) with two-bit delay difference between the two arms. The label signal is detected by another MZDI with a-half-bit delay difference between the two arms. The proposed CSK based OLS significantly increases the code efficiency of the payload signal without sacrificing the extinction ratio (ER). The feasibility of the CSK based OLS is verified by the simulation.

Optical Label Switching Based on Modified Mark Ratio Modulation

Optical Label Switching Based on Modified Mark Ratio Modulation

Design, modeling and optimization using hybrid virtual topology for QoS provision over all-optical switched networks

All-optical switched networks (AOSN), mainly optical label switching (OLS), guaranteed fast data transfer QoS support and network resource supervision. However, the emergence of new applications and services, having variable and various requirements, are produced new demands, notably in terms of QoS support and resource control. To meet these demands, a hybrid virtual topology (HVT), with multiple core node architectures employing wavelength converters (WC), fiber delay line (FDL), and deflection path (DP), is proposed. This HVT enables various node architectures to manage the availability and usage of the components, covering fixed, limited, and full range converters (FXWC, LRWC, and FRWC) also FDL. An advanced DP improves signaling and switching to supervise the potential HVT and AOSN resources while assuring QoS support. A lightpath cost is formulated to determine the potential lightpaths utilized to build the HVT guaranteeing AOSN resources and advanced traffic management. The obtained results of the conducted simulation and comparative study show that the optimized (O-HVT) approach performed better than the enhanced (E-HVT) and initial (I-HVT) approaches. Moreover, the O-HVT method optimizes AOSN resources, mainly core node architecture range, while providing QoS support for high load traffic with variable demands.

Optical label switching based on Manchester code + NRZ modulation

Optical label switching (OLS) is regarded as one promising solution for the packet-based optical switching. In this paper, a novel modulation, i.e., Manchester code + NRZ modulation is proposed for OLS. The Manchester coded payload signal the NRZ label signal are combined and then modulated onto an optical carrier by only one ASK modulator. The Manchester coded payload signal and the NRZ label signal are recovered by half-bit-delayed differential and a low-speed ASK receiver, respectively. Better than traditional orthogonal modulation, the proposed Manchester code + NRZ modulation requires no non-amplitude modulation and only one ASK modulator, reducing the equipment cost, modulation loss and operation complexity. The coding is simple and decoding is not required. According to theoretical analysis and simulation test, the induced crosstalk decreases with the bit rate ratio. The tested results verify the feasibility of the OLS based on the proposed Manchester code + NRZ modulation.

DPSK over inverse pulse position modulation with high extinction ratio for optical label switching

AbstractOptical label switching (OLS) is a promising solution for rapidly growing packet based internet traffic and data switching in data center. Most proposed schemes apply orthogonal modulation, which superimpose a nonamplitude modulated label signal onto a Manchester coded or pulse position modulated (PPM) ASK payload signal. The extinction ratio (ER) has to be reduced for overlaid signal. To avoid the quality degradation of payload signal from low ER, a differential phase shift keying (DPSK) over inverse PPM is proposed in this paper. Due to the high mark ratio of the inverse PPM, the proposed DPSK over inverse PPM modulation achieves a high ER for the ASK signal while induces limited crosstalk to the DPSK signal. Compare with the previously proposed schemes, the test results show the proposed DPSK over inverse 4PPM modulation achieves an optimum ER improvement of at least 6 dB to support an extended of at least 10.5 km.

Mark ratio modulation over pulse position modulation

• Mark ratio modulation over inverse PPM modulation is proposed for optical label switching. • Two signals are transmitted by one ASK modulation. • The mark ratio difference of PPM and inverse PPM is utilized to deliver an overlay signal. • The mark ratio modulation doesn’t degrade the PPM signal. Orthogonal modulation superimposes non-amplitude-modulated signals on Manchester coded or pulse position modulated amplitude shift keying (ASK) signals, allowing two traffic flows with different bit rates to be modulated on the same wavelength channel, and hence improving spectrum efficiency. Inspired by the orthogonal modulation, this paper proposes a novel modulation format, i.e., mark ratio modulation over pulse position modulation (PPM), which utilizes the mark ratio difference between the PPM symbols and the inverse PPM symbols to deliver an overlaid signal. Better than traditional orthogonal modulation, in the mark ratio modulation over PPM, both low-speed and high-speed traffic flows are modulated by ASK with no need to sacrifice the extinction ratio, while keeping the reception simple and easy. According to theoretical analysis and test, we found 4PPM is a good option, which can balance the trade-off between the PPM signal’s effective bit rate and the mark ratio modulated signal’s quality.

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.

Realization of FSK/ASK modulation format based on a dual-parallel modulator

We propose a novel orthogonal modulation scheme-amplitude shift keying with frequency shift keying labeling for optical label switching. The ASK payload and FSK label are simultaneously generated by a dual-parallel Mach–Zehnder modulator. The ASK payload is encoded by Manchester coding, in order to minimize the impact of “0” payload signal on the whole system performance. The transmission performance of the modulation scheme is demonstrated in this paper. The results show that this modulation scheme applying only one modulator can greatly increase the ER and the tolerance of nonlinear effect.

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.

Performance evaluations of hybrid modulation with different optical labels over PDQ in high bit-rate OLS network systems

Two orthogonal modulation optical label switching(OLS) schemes, which are based on payload of polarization multiplexing-differential quadrature phase shift keying(POLMUX-DQPSK or PDQ) modulated with identifications of duobinary (DB) label and pulse position modulation(PPM) label, are researched in high bit-rate OLS network. The BER performance of hybrid modulation with payload and label signals are discussed and evaluated in theory and simulation. The theoretical BER expressions of PDQ, PDQ-DB and PDQ-PPM are given with analysis method of hybrid modulation encoding in different the bit-rate ratios of payload and label. Theoretical derivation results are shown that the payload of hybrid modulation has a certain gain of receiver sensitivity than payload without label. The sizes of payload BER gain obtained from hybrid modulation are related to the different types of label. The simulation results are consistent with that of theoretical conclusions. The extinction ratio (ER) conflicting between hybrid encoding of intensity and phase types can be compromised and optimized in OLS system of hybrid modulation. The BER analysis method of hybrid modulation encoding in OLS system can be applied to other n-ary hybrid modulation or combination modulation systems.

Performance analysis of 112 Gb/s\xd74-channel WDM PDM-DQPSK optical label switching system with spectral amplitude code labels

We present the performance analysis of 112 Gb/s×4 wavelength division multiplexing (WDM) 100 GHz channel spacing polarization division multiplexed-differential quadrature phase shift keying (PDM-DQPSK) optical label switching system with frequency swept coherent detected spectral amplitude code labels. Direct detection is chosen to demodulate the payload by applying a polarization tracker, while 4-bits of 156 Mb/s spectral amplitude code label is coherently detected with a scheme of frequently-swept coherent detection. We optimize the payload laser linewidth as well as the frequency spacing between the payload and label. The label and payload signal performances are assessed by the eye-diagram opening factor (EOF) and bit-error rate (BER) at 10–9 as a function of the received optical power (ROP) and the optical signal to noise ratio (OSNR). The payload could well be demodulated after 900 km at a bit error rate of 10‒3 using forward error correction (FEC).

Optical Label Switching Add-Drop Multiplexer for High-Performance Metro Networks

We demonstrate a novel fast optical add-drop multiplexer (OADM) for high-capacity and low-latency next-generation metro network by exploiting optical label switching technology. The parallel optical label processing technique allows nanoseconds OADM reconfiguration time for efficient statistical multiplexing of the data packets, and facilitates per channel power monitoring for implementing nanoseconds semiconductor optical amplifier-based per channel power equalization. Experimental results of a ring network with four OADM prototypes confirm nanoseconds dynamic add/drop operation, including multicasting and power equalization for 50-Gb/s data payload. The average delivery time is $ (40-km ring), and the packet loss is $ for a load of 0.4 and 16-packet buffer.

Analysis and Execution of 80 Gb/s PDM-DQPSK Optical Label Switching System with SAC Labels

We present the performance of 80 Gb/s polarization division multiplexed-differential quadrature phase shift keying (PDM-DQPSK) optical label switching system with frequency swept coherent detected spectral amplitude code labels in simulation. 4 bits of 156 Mb/s spectral amplitude code (SAC) label are frequency-swept coherently detected. The label and payload signal performances are assessed by the eye diagram opening factor (EOF) and bit error rate (BER) as function of received optical power (ROP) and optical signal to noise ratio (OSNR). For back-to-back system and 138 km transmission, label eye opening factors are 0.94 and 0.86 respectively, while payload optical signal-to-noise ratio is 25.6 dB and the payload received optical power is -12.6 dBm for a bit error rate of 10 -9 . The payload could well be demodulated after 1,260 km transmission at a BER of 10 -3 using forward error correction (FEC).

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.

The study of multi-granularity switching based on parallel processing routing technology

A novel parallel processing optical code label-switched paths (PP-OC-LSPs) is proposed to achieve efficient conversion performance for core router and large throughput in optical network, which combines the merits of optical label switching (OLS), optical code-generalized multi-protocol label switching (OC-GMPLS), and optical code division multiplexing-paths (OCDM-paths) technology. In the proposed technology, the smallest switching granularity is an optical code which carries the label information of data packets and would be parallel converted in the core router. In the edge node, the label and payload are separated by using the optical polarity characteristics, and encoded/decoded with two different code series based on OCDM techniques so as to process them in parallel. Compared with the OLS, its switching capability has been extended to support fiber switching, wavelength switching, and OCDM switching. We present simulation results to demonstrate its performance over OCDM-paths technology.

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.

Linear random code-based label encoding scheme for label swapping free optical packet switching networks

Optical Label Switching (OLS) has been considered to be a promising approach to realize optical packet switching (OPS) networks. In an OLS router, the header processing module retrieves the routing information carried in the optical header and then replaces the old header with a new one through optical label swapping. The cost-effectiveness and the speed of performing label swapping are two major concerns. Due to lack of optical random access memory, optical label swapping has become a big challenging issue in implementing OLS switches. To overcome these difficulties, in this paper, we propose two Linear Random Code (LRC)-based label encoding schemes to achieve label swapping free OPS networks. Using the proposed schemes, a small sized label is needed. Only simple modulo-2 multiplication and modulo-2 addition operations are required to decode an optical label and there is no optical label swapping during packets traverse along the entire routing path. In our system, each source–destination pair is assigned multiple paths so the network is with traffic engineering and fault tolerance capabilities. We have carried out extensive simulations to evaluate the performance of the proposed scheme. Compared with the well-known KIS encoding scheme, the proposed LRC-based scheme can reduce the label size significantly. An 8-byte LRC label is long enough to support all node pair with five paths in a 300-node network.