Label Recognition Research Articles

Recognition of Optical Layered Binary Phase Shift Keying Labels Using Coherent Acoustooptic Processor for Hierarchical Photonic Routing

Wavelength-selective optical processing using collinear acoustooptic (AO) switches will be useful in photonic routing systems. We have studied the applications of this processing to optical label recognition in label routers. We propose the recognition of hierarchical routing labels encoded in the binary-phase-shift-keying (BPSK) format using an AO processor consisting of optical delay waveguides and parallel double-stage AO switches. Using wavelength-multiplexed hierarchical labels, simple processing using the AO processor can be realized. The recognition characteristics are analyzed and numerically confirmed by computer simulation.

High-Speed Optical Label Recognition Technique Using an Optical Digital-to-Analog Conversion and Its Application to Optical Label Switch

Operation performance of a 40 Gbps, 2-bit Optical Digital-to-Analog converter (ODAC) and its application to optical label switching systems have been investigated. The device is composed of a 1 × 2 multi-mode interference (MMI) splitter, one-bit-delay line, and a 2 × 1 MMI combiner. It has a high-mesa structure fabricated on InP-based materials. Dependence of output signal level on input signal wavelength and device temperature was measured. Due to the optical phase variation caused by the refractive index change with wavelength and temperature, output signal level varied, and it agreed well with simulation results. Four-level signals were generated and a quarter dependence of phase on temperature and wavelength compared with that for 10-Gbit/s was verified. Next, operation tolerance of the ODAC as an optical label processor, bit error rate (BER) of the digital-to-analog (DA)-converted signal was simulated. The tolerance against fluctuation of light source power, optical phase in the device, optical chirp, and extinction ratio of input signal was estimated. For all parameters, operation tolerance could be kept, but that for 40 Gbps is smaller than that for 10 Gbps. Then, autonomous label processing and optical label switching performance using a gate pulse generation scheme based on phase-shifted preamble was investigated. Optical DA conversion and three kinds of optical label were recognized at a bit rate of 40 Gbps, and optical packet transfer could be confirmed.

Parallel-to-Cascading Optical Code Label Processing in Optical Packet Switching Networks

Parallel-to-cascading optical code (OC) label processing based on fiber Bragg grating is proposed and experimentally demonstrated. With this technique, the length of the multibit OC label is the same as that of the one-bit OC label; only one encoder and one decoder are needed for the multibit OC label's generation and recognition; the relatively low-speed recognition patterns also reduce the complexity of generating the control signal. The experimental results show that both the ratio of autocorrelation peak to cross-correlation peak (ACP/CCP) and the ratio of ACP to maximum autocorrelation wing are higher than 8 dB in the multibit label's decoded signal, so the parallel-to-cascading OC label processing is practical for optical packet switching networks.

Multibit Information Optical Code Label Processing in Optical Packet Switching Networks

Multibit optical code (OC) label and its en/decoder based on fiber Bragg grating is proposed and experimentally demonstrated. The multisampling technique is introduced into the label's encoder, then the maximum number of bits that one label can carry is significantly increased. The label's multibit information can be recognized by a single cascaded decoder. The experimental results show that a higher than 10-dB ratio of autocorrelation peak to cross-correlation peak and a higher than 9-dB ratio of autocorrelation peak to maximum autocorrelation wing can be realized simultaneously for label's recognition, so the multibit OC label is practical for optical packet switching networks.

Wavelength Dependence of Optical Waveguide-Type Devices for Recognition of QPSK Routing Labels

In photonic label routing networks, recognition of optical labels is one of the key functions. We have proposed passive waveguide-type devices for recognition of optical labels coded in quadri-phase-shift-keying (QPSK) form. In this paper, we consider wavelength dependence of the devices. The basic module of the proposed device consists of a 3-dB directional coupler, two Y-junctions, and an asymmetric X-junction. The Y-junction and an asymmetric X-junction have basically no wavelength dependence. Although the 3-dB directional coupler has weak wavelength dependence, the device for two-symbol label recognition is found to work in wavelength 1.5-1.6 μm. The performance of the device is confirmed by simulation using beam propagation method (BPM).

Wavelength-Insensitive Integrated-Optic Circuit Consisting of Asymmetric X-Junction Couplers for Recognition of BPSK Labels

We have proposed a label recognition integrated-optic circuits for photonic label switching using self-routing of the label pulses. Binary phase shift keying (BPSK) format is considered as the label. An identifying bit is placed ahead of the address bits in the label. The label recognition system consists of a tree-structure connection of asymmetric X-junction couplers. The system uses self-routing propagation of the identification bit controlled by the address bits. Asymmetric X-junction couplers have a feature of small dependence on wavelength. However, the wavelength dependence of optical circuits consisting of multiple asymmetric X-junction couplers depends strongly on its architecture. In this paper, we propose a wavelength insensitive architecture of the recognition circuit. The wavelength independence in the improved circuit is confirmed using finite-difference beam propagation method (FD-BPM). We numerically demonstrate that our proposed system can recognize all the binary-code labels in wavelength range of 1500-1600 nm with crosstalk less than -25 dB and -15 dB for label length three and four, respectively.

Recognition of Wavelength-Multiplexed Hierarchical Label with Acoustooptic Waveguide Circuit

High-speed optical processing for packet routing can overcome the bottleneck in large-capacity photonic networks. We have studied collinear acoustooptic (AO) switches and applications to optical label recognition. Since the parallel combination of collinear AO switches can handle wavelength-division-multiplexed (WDM) optical pulses, the recognition of optical labels encoded in spectral and time domains can be realized. In this report, we discuss the recognition of layer-structure labels for hierarchical routing control. By employing WDM time-series labels including identifying bits, labels corresponding to each layer can be recognized. The recognition characteristics are confirmed by computer simulation.

Photonic Label Recognition by Time-Space Conversion and 2-D Spatial Filtering With Delay Compensation

An optical-label recognition system using time-to-space conversion, spatial Vander-Lugt 2-D correlation, and postprocessing with a slit and a delay compensator is proposed. The postprocessing, with the narrow slit and a prism for the time-delay compensation, makes it possible to distinguish the labels, consisting of a time series of optical pulses. For 4-b binary phase-shift-keying labels at 160 Gb/s, eight different labels are proved to be distinguished by the computer simulation. The contrast ratio of autocorrelation to cross-correlation is 1.61 and 2.5 without and with time gating, respectively.

Field Trial of 640-Gbit/s-Throughput, Granularity-Flexible Optical Network Using Packet-Selective ROADM Prototype

Reconfigurable optical add/drop multiplexers (ROADMs) are able to provide flexible wavelength path provisioning in wavelength division multiplexing (WDM) networks. However, the capability of conventional ROADMs is limited to handling wavelength paths, and it does not support fine granularity in add/drop multiplexing of packets. Recently, we have proposed and demonstrated a packet-selective ROADM that combines an acoustooptic wavelength-tunable filter (AOTF) and an optical packet ADM (PADM) using optical code label processing. It provides more efficient utilization of wavelengths than conventional ROADMs. However, the bit rate of the demonstration was limited up to 10 Gbit/s. In this paper, we newly develop a label-selectivity-enhanced optical en/decoder, which allows the optical label recognition with 40-Gbit/s nonreturn-to-zero (NRZ) data packets, and a wide pass-band AOTF for 40-Gbit/s signals. Furthermore, we develop 640-Gbit/s throughput, packet-selective ROADM prototype, and demonstrate a field trial of granularity-flexible 3-node optical network over 173 km. error-free packet ADMs (error rate of under 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-12</sup> ) for all 16-wavelength channels at all nodes are obtained.

Waveguide-Type Optical Circuit for Recognition of Optical QPSK Coded Labels in Photonic Router

In photonic label routing networks, optical recognition of optical labels is one of the key functions. We propose a In photonic label routing networks, optical recognition of optical labels is one of the key functions. We propose a passive waveguide-type device for recognition of optical coded labels. We consider quadrature-phase-shift-keying (QPSK) coded labels. The basic module of the proposed device consists of a 3-dB directional coupler, two Y-junctions, and an asymmetric X-junction. By using interference between an optical pulse of each coded bit and a identifying bit pulse, the basic module distinguishes optical phase of the QPSK signal in a self-routing fashion of the identifying bit pulse. QPSK codes consisting of plural bits can also be recognized by connecting the basic module device in a tree structutre through a phase adjustment circuit. The performance of the proposed basic module is confirmed by simulation using beam propagation method (BPM).passive waveguide-type device for recognition of optical coded labels. We consider quadrature-phase-shift-keying (QPSK) coded labels. The basic module of the proposed device consists of a 3-dB directional coupler, two Y-junctions, and an asymmetric X-junction. By using interference between an optical pulse of each coded bit and a identifying bit pulse, the basic module distinguishes optical phase of the QPSK signal in a self-routing fashion of the identifying bit pulse. QPSK codes consisting of plural bits can also be recognized by connecting the basic module device in a tree structure through a phase adjustment circuit. The performance of the proposed basic module is confirmed by simulation using beam propagation method (BPM).

Recognition of Wavelength-multiplexed Labels with Acoustooptic Waveguide Circuit for Hierarchical Photonic Routing

High-speed optical processing for packet routing can overcome bottleneck in large- capacity photonic networks. We have studied on collinear acousto-optic (AO) switches and applications to optical label recognition. Since parallel combination of collinear AO switches can handle wavelength-division-multiplexed (WDM) optical pulses, recognition for optical labels encoded in spectral and time domains can be realized. In this report, we discuss recognition of layer-structure labels for hierarchical routing control. By employing WDM time-series labels in- cluding identifying bits, the labels corresponding to each layer can be recognized. The recognition characteristics are conflrmed by computer simulation.

Integrated-optic digital-to-analogue converter for recognising multiwavelength pulse patterns

A planar lightwave circuit based device is proposed that can recognise optical multiwavelength pulse patterns based on digital-to-analogue conversion. The device consists of a splitter with variable splitting ratios, delay lines and an arrayed-waveguide grating based wavelength multiplexer, and requires no optical gates. 80 Gbit/s and four-bit label recognition experiments were successfully carried out with the device.

Ultrafast Forwarding Architecture Using a Single Optical Processor for Multiple SAC-Label Recognition Based on FWM

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> We propose and demonstrate a novel ultrafast label processor that can recognize multiple spectral amplitude coded (SAC) labels using four wave mixing (FWM) sideband allocation and selective optical filtering. Our proposed solution favors hardware simplicity over bandwidth efficiency in order to achieve ultrafast label recognition at reasonable cost. Our implementation, unlike all other optical label processing techniques, does not require time gating, envelope detectors, or serial-to-parallel converters. Labels are transmitted simultaneously with the payload, improving temporal efficiency at the expense of spectral efficiency. Note that bandwidth efficiency can be improved through a frequency management scheme that uses irregular spacing of wavelengths for payload and label, a complexity overhead in management similar to that in long-haul networks employing irregular spacing of carriers to avoid FWM products. We present two experiments of the single processor for ultrafast forwarding using first optoelectronic and then all-optical switches. In the first experiment, we use 10 SAC labels with minimum bin separation of 25 GHz, 10 Gb/s variable-length data packets, and forward packets over 200 km using electrooptical switches. In the second experiment, all-optical switching at 40 Gb/s is demonstrated using a SAC family for up to 36 labels. We present details on the families of spectral codes for label recognition, using unequally spaced frequency bins. A code family with weight 2 and length 9 uniquely identifies 36 labels. Hardware complexity is moderate compared with short-pulse code labels (mode-locked laser) techniques. Two stable tunable lasers are required for label generation of this code family; all other hardware is commercial, off-the-shelf components such as semiconductor optical amplifiers, array waveguide gratings, optoelectronic switches, and photodetectors. </para>

Optical Label Recognition Using Tree-Structure Self-Routing Circuits Consisting of Asymmetric X-Junctions

We propose a new label recognition system for photonic label routing network. Binary-coded labels in binary phase-shift-keying format are considered. The system consists of an optical waveguide circuit with tree-structure passive asymmetric X-junctions and time gates. The system uses self-routing propagation of an identifying bit by performing interference with address bits. The identifying bit is placed in advance of the address bits in the label. The identifying bit pulse is routed to the destination output port corresponding to the code of the address. The operation principle is described. It is shown that all the binary number codes can be recognized with this system. We discuss the feasibility of the system by evaluating its crosstalk. To reduce the crosstalk, an improved scheme is also presented. The label recognition operation with the optical waveguide device is verified by numerical simulation using the finite-difference beam propagation method.

All-Optical Label Recognition Using Self-Routing Architecture of Mach-Zehnder Interferometer Optical Switches with Semiconductor Optical Amplifiers

We propose a new label recognition system for photonic label switching using self-routing of labels. Binary-coded labels in on-off keying format are considered. The system consists of an all-optical demultiplexer (DeMUX) and an address recognition unit (ARU) consisting of tree-structured switches. The system uses self-routing propagation of an indication bit controlled with address bits. The indication bit is placed in advance of the address bits in the label. In DeMUX, all-optical switches in a configuration of Mach-Zehnder interferometer with semiconductor optical amplifiers (SOA-MZI) are controlled by the indication bit pulse to separate each of the label bits. The indication bit pulse is routed to the destination output port corresponding to the code of the address in ARU. It is shown that all the binary number codes can be recognized with this system. The operation principle is verified by numerical simulation using coupled-mode theory and a rate equation. Moreover, the switching crosstalk is also evaluated.

Recognition of Wavelength-Division-Multiplexed Time-Series Optical Coded Labels Using Collinear Acoustooptic Devices without Time Gating for Photonic Routing

Optical label processing has been expected to increase the throughput of packet routing in photonic networks. We have studied label recognition using collinear acoustooptic (AO) devices, where the label is encoded in time and spectral domains. In the label recognition system in the time domain, time-gating devices are required to improve the recognition characteristics. In this report, we propose a label recognition system for optical codes encoded in time and spectral domains where the time-gating function is not required. We discuss the recognition characteristics using the results of numerical analysis. The proposed system will be useful in increasing the number of distinguishable codes and improving the flexibility of routing control in the networks.

Label recognition using collinear acoustooptic devices in WDM photonic router

AbstractCollinear acoustooptic (AO) switches are investigated for use in label recognition system in photonic routing systems. The optical label discussed in this paper uses optical codes which are encoded in the time domain. Short optical pulse trains representing the codes are processed with integrated AO devices. Proposed device configurations for label recognition are described with the basic operation mechanism. A numerical example for the code recognition is also presented. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 159(3): 48–55, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20453

Code Recognition for Optical Time-Series WDM Coded Label Using Acoustooptic Switch Array

Optical label processing has been expected to increase the throughput of packet routing in photonic networks. We have studied label recognition using collinear acoustooptic (AO) devices, where the label is encoded in time and spectral domains. In the label recognition system in time domain, time gating devices were required to improve the recognition charac- teristics. In this report, we investigate a label recognition system for optical codes encoded in time and spectral domains where time gating function is not required. We discuss the recogni- tion characteristics using numerical analysis. The proposed system will be useful to increase the number of distinguishable codes and to improve the ∞exibility of routing control in the networks.

Design of All-Optical Contention Detection and Resolution for 40-Gb/s Label-Switched Routers

We present a new scheme for all-optical contention detection and time-domain contention resolution of optical packets in label-switched routers that employ all-optical label recognition. The contention detection subsystem provides all the necessary control signals required to drive an optically controlled buffer which employs 1 times 2 optical switching elements and an optical fiber delay line. The state of the buffer is dynamically controlled on a per-packet basis with all the decisions and processing performed in the optical domain. Physical layer simulations show successful buffering and forwarding of 40-Gb/s optical packets with 2-dB power penalty

Wavelength-Division-Multiplex Photonic Routers with Collinear Acoustooptic Processing for Optical Label Matching in Spectral and Time Domains

A collinear acoustooptic (AO) switch has a feature of wavelength-selective switching for wavelength-division-multiplexed (WDM) signals. This feature can be used for photonic packet routing in WDM photonic networks. In this study, the application of collinear AO switches to a label recognition processor in a photonic routing system is investigated. An optical label is assumed to be encoded in spectral and time domains. Collinear AO switches are considered for use in label recognition by using multiple wavelength switching with rf control signals at multiple frequencies. By employing a combination of encoding in spectral and time domains, flexibility in routing control, and the number of represented labels can be increased. Numerical examples of label recognition are also presented.