Optical Label Switching Research Articles

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 Packet Switching Networks With Binary Multiwavelength Labels

We propose a network structure for routing optical packets based on binary multiwavelength labels. We resolve the main drawbacks of previously proposed optical label switching scenarios: high splitting loss and complex, expensive hardware. In our scheme, the label is mapped bit-by-bit to a selection of wavelength bins. Variable-length packets are self-forwarded via a multistage switch. This structure is scalable, high-speed, simple, practical, and low-cost, exploiting the workhorses of today's optical communications systems: arrayed waveguide gratings, distributed feedback lasers, LiNbO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> switches, and low-speed photodiodes and electronics (~ 100 MHz). We also propose a solution to alleviate the sophisticated label swapping processing required in generalized multiprotocol label switching (GMPLS) networks. We time-multiplex the binary multiwavelength labels for the entire optical label switching path. We examine the performance of both schemes experimentally by verifying successful routing and error-free transmission.

Investigation of the influence of key parameters on system performance in all-optical label switching based on FSK/ASK orthogonal modulation format

The transmission characteristics of the optical label switching system based on the FSK/ASK orthogonal modulation format is investigated. The factors that affect the transmission performance, such as the FSK tone space, dispersion compensation and coupler split ratio, are studied by numerical simulation. The proposed scheme is also experimentally demonstrated with a transmission of 155 Mbit/s FSK label combined with 10 Gbit/s ASK payload.

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.

DPSK/FSK Hybrid Modulation Format and Analysis of Its Nonlinear Performance

We propose a novel hybrid modulation format-differential phase shift keying with frequency shift keying labeling for optical label switching. A modulation technique based on a dual-parallel Mach-Zehnder modulator and a label erasing scheme are presented. The tolerance of the new format to intrachannel four-wave mixing at high speeds is studied analytically and through simulations, which show robustness to nonlinear impairments.

Reliable Multipath Provisioning for High-Capacity Backbone Mesh Networks

We investigate reliable multipath provisioning of traffic in high-capacity backbone mesh networks, e.g., next-generation SONET/SDH networks supporting virtual concatenation (VCAT). VCAT enables a connection to be inversely multiplexed on to multiple paths, a feature that may lead to significantly improved performance over conventional single-path provisioning. Other mesh networks such as those employing optical wavelength-division multiplexing (WDM) and multiprotocol label switching (MPLS) can also benefit from this multipath provisioning approach. We propose effective multipath bandwidth as the metric to provision a connection while satisfying its reliability requirements (measured in terms of availability). We demonstrate that effective multipath bandwidth provides more flexibility and lower blocking probability without the cost and the complexity associated with traditional protection schemes developed for optical WDM and MPLS networks. We also investigate the practical problem of provisioning effective multipath bandwidth with cost constraints. We analyze the tractability of the problem and present a heuristic which results in significantly reduced number of blocked connections due to cost constraints.

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

Architecture of a Dual-Stage Optical Label Switch Using Out-of-Band Wavelength and Code Optical Properties

A method of generating circuits in an optical network is optical multiple-protocol lambda switching (OMPlambdaS). For OMPlambdaS, the wavelength of the optical carrier is used as an out- of-band label to route data through the network without requiring periodic conversion to the electrical state. A method of adding a second dimension of optical encoding as an out-of-band label used for routing data through a label-switched network is presented. Combining wavelength and code multiplexing techniques generates an O <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> circuit-switched network with a data capacity of up to 5.7 Tb/s on each point-to-point link in the network. The proposed architecture uses two stages to process and map labels for each bit transmitted through the network. The architecture and simulation results for the dual-stage optical label switch (DSOLS) are presented.

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.

Optical Packet and Burst Switching Technologies for the Future Photonic Internet

This paper reviews advanced optical burst switching (OBS) and optical packet switching (OPS) technologies and discusses their roles in the future photonic Internet. Discussions include optoelectronic and optical systems technologies as well as systems integration into viable network elements (OBS and OPS routers). Optical label switching (OLS) offers a unified multiple-service platform with effective and agile utilization of the available optical bandwidth in support of voice, data, and multimedia services on the Internet Protocol. In particular, OLS routers with wavelength routing switching fabrics and parallel optical labeling allow forwarding of asynchronously arriving variable-length packets, bursts, and circuits. By exploiting contention resolution in wavelength, time, and space domains, the OLS routers can achieve high throughput without resorting to a store-and-forward method associated with large buffer requirements. Testbed demonstrations employing OLS edge routers show high-performance networking in support of multimedia and data communications applications over the photonic Internet with optical packets and bursts switched directly at the optical layer

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

Same Wavelength Packet Switching in Optical Label Switched Networks

The authors propose a novel optical-label-swapping scheme for the same wavelength packet switching using optical carrier suppression and separation technique and without requiring any conventional wavelength converter in a scalable optical-label-switched network that carries a differential phase-shift keying modulated payload and an on-off keying modulated label. The performance of the proposed scheme is investigated using both experimental demonstration and numerical simulation. These experimental and simulation results show that the proposed optical-label-swapping scheme is suitable for the same wavelength packet switching in future scalable metro and core optical transport networks

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

On intranode impairments and engineering rules for an optical label switching router supporting an FSK/IM labeling scheme

This paper presents a study on intranode impairments and engineering rules for a label switching router supporting intensity modulated (IM) optical payload data signals labeled by using frequency-shift key (FSK) modulation. Engineering rules and design guidelines are presented regarding the choice of system parameters such as IM extinction ratio, FSK frequency deviation, alignment of optical filtering stages, label swapping, and node cascadability. The presented rules are derived from insights obtained from computer simulations and experimental validation for a 10-Gb/s IM payload signal

Optical label switching of DRZ/DPSK orthogonal signal generated by photonic-crystal fiber

We demonstrate orthogonal label switching by using a dark-return-to-zero (DRZ) payload and differential phase-shift keying (DPSK) label generated by a dispersion-flattened photonic-crystal fiber. The high extinction ratio of both the payload and label improves the receiver margin. The DRZ payload introduces little cross talk to the DPSK label due to the RZ-like output of the demodulated DPSK. Simulations are performed to study the eye-closure penalty of the payload and label at different DRZ pulse widths. We compare the DRZ/DPSK with the RZ and DPSK signals numerically at the same data rate and show that the DRZ/DPSK has a strong tolerance to the polarization-mode dispersion. The DRZ/DPSK has a more compact spectrum suitable for the strong filtering requirements in WDM systems.

101-hop cascaded operation of an optical-label switching router with all-optical clock recovery and 3R regeneration

This paper experimentally demonstrates the cascaded operation of an optical-label switching router for up to 101hops with 3R regeneration (reamplification, reshaping, and retiming). A semiconductor optical amplifier-based Mach-Zehnder interferometer wavelength converter performs the reshaping. A Fabry-Peacuterot filter all-optically recovers the clock from the incoming packets. Synchronous modulation by a LiNbO3 modulator using the recovered clock performs the retiming. The 3R regeneration maintains good signal quality in the cascaded operation, which is important for scalable optical networking

Enabling Technologies for Next-Generation Optical Packet-Switching Networks

The optical packet-switching network is considered to be one of the most promising solutions for end-to-end delivery of high-bitrate data, video, and voice signals across optical networks of the future. Optical label switching (OLS) technology incurs simpler extraction and processing of the labels so that the optical packets can be routed with low latency to the destinations. We have developed several key enabling technologies for integrated optical networks, including optical label generation, label swapping, optical buffering, clock recovery, and wavelength conversion. We have designed and experimentally demonstrated these enabling techniques that can provide efficient broadband services in future optical networks.

Single modulator payload/label encoding and node operations for optical label switching

We present and analyze payload/label encoding based on a single Mach-Zehnder modulator, in which the payload is differential phase-shift keyed and the label is amplitude-shift keyed through modulation of either the modulator bias or the amplifier gain. The encoding is analyzed numerically and experimentally. Simultaneous encoding of a 10-Gb/s payload and a 155-Mb/s label is demonstrated with high receiver sensitivities. Penalty-free transmission over 80 km of standard single-mode fiber is achieved for both the payload (with dispersion compensation) and the label (without dispersion compensation). Furthermore, polarization-independent label processing and payload wavelength conversion at intermediate nodes are proposed for potentially cost-effective node operations.