Showing papers on "Optical switch published in 2003"

Optical switching: switch fabrics, techniques, and architectures

Abstract: The switching speeds of electronics cannot keep up with the transmission capacity offered by optics. All-optical switch fabrics play a central role in the effort to migrate the switching functions to the optical layer. Optical packet switching provides an almost arbitrary fine granularity but faces significant challenges in the processing and buffering of bits at high speeds. Generalized multiprotocol label switching seeks to eliminate the asynchronous transfer mode and synchronous optical network layers, thus implementing Internet protocol over wavelength-division multiplexing. Optical burst switching attempts to minimize the need for processing and buffering by aggregating flows of data packets into bursts. In this paper, we present an extensive overview of the current technologies and techniques concerning optical switching.

Optimal bistable switching in non-linear photonic crystals

Abstract: An optical bi-stable switch includes a photonic crystal cavity structure using its photonic crystal properties to characterize a bi-stable switch so that optimal control is provided over input and output of the switch. A plurality of waveguide structures are included, at least one of the waveguide structures providing the input to the switch and at least one providing the output to the switch.

All-optical transistor action with bistable switching in a photonic crystal cross-waveguide geometry

Abstract: We demonstrate all-optical switching action in a nonlinear photonic crystal cross-waveguide geometry with instantaneous Kerr nonlinearity, in which the transmission of a signal can be reversibly switched on and off by a control input. Our geometry accomplishes both spatial and spectral separation between the signal and the control in the nonlinear regime. The device occupies a small footprint of a few micrometers squared and requires only a few milliwatts of power at a 10-Gbit/s switching rate by use of Kerr nonlinearity in AlGaAs below half the electronic bandgap. We also show that the switching dynamics, as revealed by both coupled-mode theory and finite-difference time domain simulations, exhibits collective behavior that can be exploited to generate high-contrast logic levels and all-optical memory.

High-contrast all-optical bistable switching in photonic crystal microcavities

Abstract: We present a bistable photonic crystal configuration consisting of a waveguide sided coupled to a single-mode cavity with instantaneous Kerr nonlinearity. We show that such a configuration can generate extremely high contrast between the bistable states in its transmission with low input power. We also provide an analytic theory that can completely account for the entire transient switching dynamics, as revealed by finite difference time domain simulations.

Fibre channel arbitrated loop bufferless switch circuitry to increase bandwidth without significant increase in cost

Abstract: A switch, switched architecture and process for transferring data through an FCAL switch is disclosed. The switch uses multiple switch control circuits each coupled to one FCAL network and all connected to a crossbar switch. The switch control circuits are coupled together by a protocol bus for coordination purposes. Local conversations can occur on each FCAL loop and crossing conversations through the switch can occur concurrently. The OPN primitive is used to establish the connection before any data is transferred thereby eliminating the need for buffer memory in the switch control circuits. The destination address of each OPN is used to address a lookup table in each switch control circuit to determine if the destination node is local. If not, the destination is looked up and a connection request made on the protocol bus. If the remote port is not busy, it sends a reply which causes both ports to establish a data path through the backplane crossbar switch.

Optical packet switching and buffering by using all-optical signal processing methods

Abstract: We present a 1 /spl times/ 2 all-optical packet switch. All the processing of the header information is carried out in the optical domain. The optical headers are recognized by employing the two-pulse correlation principle in a semiconductor laser amplifier in loop optical mirror (SLALOM) configuration. The processed header information is stored in an optical flip-flop memory that is based on a symmetric configuration of two coupled lasers. The optical flip-flop memory drives a wavelength routing switch that is based on cross-gain modulation in a semiconductor optical amplifier. We also present an alternative optical packet routing concept that can be used for all-optical buffering of data packets. In this case, an optical threshold function that is based on a asymmetric configuration of two coupled lasers is used to drive a wavelength routing switch. Experimental results are presented for both the 1 /spl times/ 2 optical packet switch and the optical buffer switch.

Fast and low-power thermooptic switch on thin silicon-on-insulator

Abstract: We have designed and fabricated Mach-Zehnder interferometer thermooptic switches using a wafer-bonded thin-silicon-on-insulator materials system. The thermally switched devices use single-mode strip waveguides with dimensions 0.26/spl times/0.6 /spl mu/m/sup 2/, operating at a wavelength of /spl lambda/=1.55 /spl mu/m. Useful device characteristics include a low switching power, 50 mW, and a fast rise time of <3.5 /spl mu/s. These results demonstrate the potential of this high-index-contrast materials system for the design of fast and low-power thermooptic switches and as an active element in photonic integrated circuits.

Nonlinear polarization rotation in semiconductor optical amplifiers: theory and application to all-optical flip-flop memories

Abstract: We present a model for polarization-dependent gain saturation in strained bulk semiconductor optical amplifiers. We assume that the polarized optical field can be decomposed into transverse electric and transverse magnetic components that have indirect interaction with each other via the gain saturation. The gain anisotropy due to tensile strain in the amplifier is accounted for by a population imbalance factor. The model is applied to a nonlinear polarization switch, for which results are obtained, that are in excellent agreement with experimental data. Finally, we describe an all-optical flip-flop memory that is based on two coupled nonlinear polarization switches.

Optical switching technology comparison: optical MEMS vs. other technologies

Abstract: Optical switching technologies are very crucial to future mobile broadband all-optical IP networks. Many different optical switching technologies are currently available or under development. The main purpose of the article is to conduct performance comparisons on optical switching technologies in terms of basic performance, network requirements, and system requirements based on a literature survey. The technologies include switching based on optical microelectromechanical systems (MEMS), thermal optical switching, electro-optic switching, and acousto-optic switching technologies. Each optical switching technology has unique performance characteristics specific to the utilized optical phenomena. It might be crucial to integrate some technologies together to achieve a better solution for optical switching. Optical switching is a very hot topic attracting much research effort. Optical MEMS-based switching technology might be one of the most promising approaches at present. Many new optical switching technologies might be created in the near future. Through the impact of nanotechnology, some innovative approaches to optical switching might emerge.

Digital processing with a three-state molecular switch.

Abstract: Certain molecular switches respond to input stimulations producing detectable outputs. The interplay of these signals can be exploited to reproduce basic logic operations at the molecular level. The transition from simple logic gates to complex digital circuits requires the design of chemical systems able to process multiple inputs and outputs. We have identified a three-state molecular switch that responds to one chemical and two optical inputs producing two optical outputs. We have encoded binary digits in its inputs and outputs applying positive logic conventions and demonstrated that this chemical system converts three-digit input strings into two-digit output strings. The logic function executed by the three-state molecular switch is equivalent to that of a combinational logic circuit integrating two AND, two NOT, and one OR gate. The three states of the molecular switch are a colorless spiropyran, a purple trans-merocyanine, and its yellow-green protonated form. We have elucidated their structures b...

Time sliced optical burst switching

Abstract: Time Sliced Optical Burst Switching is a proposed variant of optical burst switching, in which switching is done in the time domain, rather than the wavelength domain. This eliminates the need for wavelength converters, the largest single cost component of systems that switch in the wavelength domain. We examine some of the key design issues for routers that implement time sliced optical packet switching. In particular, we focus on the design of the Optical Time Slot Interchangers (OTSIs) needed to effect the required time domain switching. We introduce a novel nonblocking OTSI design and also show how blocking OTSIs can be used to implement the required switching operations. We study the performance of systems using blocking OTSIs and demonstrate that near ideal statistical multiplexing performance can be achieved using even quite inexpensive, blocking OTSI designs. These results suggest that optical technology may one day be able to provide a cost-effective alternative to electronics in packet switching systems.

Electro-optical switching using coupled photonic crystal waveguides

Abstract: An electro-optical switch (10) implemented in coupled photonic crystal waveguides (12, 14) is disclosed. The switch (10) is proposed and analyzed using both a finite-difference time-domain ('FDTD') method and a plane wave expansion ('PWM') method. The switch (10) may be implemented in a square lattice (18) of silicon posts in air, as well as in a hexagonal lattice (38) of air holes in a silicon slab. Switching occurs due to a change in the conductance in the coupling region between the photonic crystal waveguides (12, 14), which modulates the coupling coefficient and eventually causes switching. Conductance may be induced electrically by carrier injection or optically by electron-hole pair generation. The electro-optical switch (10) has low insertion loss and optical crosstalk in both the cross and bar switching states.

Beam-steering micromirrors for large optical cross-connects

Abstract: This paper describes Si-micromachined two-axis beam-steering micromirrors and their performance in 256 /spl times/ 256- and 1024 /spl times/ 1024-port large optical cross-connects (OXCs). The high-reflectivity wavelength-independent mirrors are electrostatically actuated; capable of large, continuous, controlled, dc tilt in any direction at moderate actuation voltages; and allow setting times of a few milliseconds. Packaged two-dimensional (2-D) arrays containing independently addressable identical 256 and 1296 mirrors are used to build fully functional bitrate and wavelength-independent single-stage, low-insertion-loss, single-mode fiber OXC fabrics.

Optical switch fabrics for ultra-high-capacity IP routers

Abstract: Next-generation switches and routers may rely on optical switch fabrics to overcome scalability problems that arise in sizing traditional electrical backplanes into the terabit regime. In this paper, we present and discuss several optical switch fabric technologies. We describe a promising approach based on arrayed waveguide gratings and fast wavelength tuning and explain the challenges with respect to technical and commercial viability. Finally, we demonstrate an optical switch fabric capable of 1.2-Tb/s throughput and show packet switching with four ports running at 40 Gb/s each.

Demonstration of a nanophotonic switching operation by optical near-field energy transfer

Abstract: We have demonstrated the operation of a nanophotonic switch that uses three CuCl quantum cubes with a size ratio of 1:√:2. The switching mechanism is based on resonant optical near-field energy transfer between the resonant quantized excitonic energy levels of the quantum cubes. Using near-field optical spectroscopy, we observed a switching rise time of less than 100 ps and a repetition rate of 80 MHz. These results suggest the possibility of making a nanophotonic switching device smaller than 20 nm with a figure of merit 10–100 times higher than that of a conventional photonic switch.

Tunable filter, manufacturing method thereof and optical switching device comprising the tunable filter

Abstract: The invention provides a tunable filter that can minimize adjacent channel cross talk despite an increase of a number of available wavelengths and quickly switch a wavelength to be used, and manufacturing method thereof, and also an optical switching device comprising such tunable filter. In a tunable filter having a Fabry-Perot etalon structure, not less than two cavity gaps 114 to 116 are provided and separation between the cavity gaps is controlled by any of electrostatic drive, electromagnetic drive or piezoelectric drive. In this case, the cavity gaps can be formed through the steps of forming a sacrificial layer in advance where a cavity gap is to be formed; forming a plurality of optical multilayer films 100 to 103 ; and removing the sacrificial layer by etching. Substrates 107 and 109 are combined through a supporting column 108.

Advanced fiber optical switches using deep RIE (DRIE) fabrication

Abstract: Optical switch is widely used in the optical fibre communication networks. This paper described an advanced microelectromechanical systems (MEMS) optical switch that consists of actuator, suspension beam, micromirror, and fiber grooves using deep RIE (DRIE) etching fabrication process. Based on the specification and design requirements of optical switch, the DRIE etching fabrication process is combined with the anisotropic and isotropic, the two different types of etching methods that improve the surface roughness of the micro mirror. Net structure with arcs is introduced to obtain a good release and microloading effect is used and prevented trickily. As a result, promising performances of the optical switch such as low driving voltage of 30 V, low insertion loss, fast switching speed of less than 100 μs and high reliable operation of more than 20 million cycles are achieved. The actuator of the optical switch enables to the delivery of a moving displacement which is as large as 45 μm. This MEMS optical switch has a broad applications for fibre optical communication systems such as n×n optical crossconnects (OXCs), variable optical attenuator (VOA), etc.

Method and circuit for optimizing power efficiency in a DC-DC converter

Abstract: In one embodiment, a turn-on delay control structure ( 30 ) includes a sense FET device ( 31 ) that is coupled to a switch node ( 13 ) in a synchronous DC-DC converter ( 10 ). The DC-DC converter includes a high-side switch ( 11 ) and a low-side switch ( 12 ). The sense FET device ( 31 ) senses current conduction in a body diode ( 18 ) of the low-side switch ( 12 ). A current sensing/comparator circuit ( 32 ) coupled to the sense FET ( 31 ) detects changes in current conduction. A delay circuit ( 33 ) and a clock/logic circuit ( 32 ) coupled to the current sensing/comparator circuit ( 32 ) predict and adjust delay time in switching between the high-side switch ( 11 ) and the low-side switch ( 12 ).

Switched optical backbone for cost-effective scalable core IP networks

Abstract: With the advent of WDM technology, IP backbone carriers are now connecting core routers directly over point-to-point WDM links (IP over WDM). The advances and standardization in optical control plane technologies like GMPLS have substantially increased the intelligence of the optical layer and shown promise toward making dynamic provisioning and restoration of optical layer circuits a basic capability to be leveraged by upper network layers. In light of this, an architecture where a reconfigurable optical backbone (IP over OTN) consisting of SONET/SDH crossconnects/switches interconnected via DWDM links provides connectivity among IP routers is an emerging alternative. As carriers evolve their networks to meet the continued growth of data traffic in the Internet, they have to make a fundamental choice between the above architectural alternatives. In the current business environment, this decision is likely to be guided by network cost and scalability concerns. A reconfigurable optical backbone provides a flexible transport infrastructure that eases many operational hurdles, such as fast provisioning, robust restoration, and disaster recovery. It can also be shared with other service networks such as ATM, frame relay, and SONET/SDH. From that perspective, an agile transport infrastructure is definitely the architecture of choice. The IP-over-OTN solution is also more scalable since the core of the network in this architecture is based on more scalable optical switches rather than IP routers. But what about cost? Since the IP-over-OTN solution introduces a new network element, the optical switch, is it more expensive? We address that question by comparing IP-over-WDM and IP-over-OTN architectures from an economic standpoint using real-life network data. We show that contrary to common wisdom, IP over OTN can lead to substantial reduction in capital expenditure through reduction of expensive transit IP router ports. The savings increases rapidly with the number of nodes in the network and traffic demand between nodes. The economies of scale for the IP-over-OTN backbone increase substantially when we move traffic restoration from the IP layer to the optical layer. We also compare the two architectures from the perspective of scalability, flexibility, and robustness. Our observations make a strong case in favor of a switched optical backbone for building scalable IP networks.

Intelligent optical data switching system

Abstract: The present invention enables a multi-wavelength band to be maintained as an optical signal through only a band switch, and provides a switch node with expandable capacity for switching data optically.

Performance analysis of optical burst switched node with deflection routing

Abstract: As the optical network evolves from static long haul connection provider to an adaptive and "smart" backbone solution, optical burst switching (OBS) becomes an attractive scheme for its flexibility and efficiency. However, how to reduce data loss is a crucial issue in such an asynchronous and one-way reservation system. In this paper, we study one contention resolution strategy in OBS networks: deflection routing. We extend an existing work to provide approximate and accurate models for the data loss analysis of single OBS node with and without wavelength conversion capability. The accuracy of our models is evaluated by simulation results.

Hybrid electronic/optical switch system

Abstract: A high speed optical communication and data transfer network comprises fiber optic links interconnecting a plurality of hybrid electronic-optical switch devices, each hybrid switch circuit including an electronic switch, electronic switch controller and optical switch. The hybrid switch circuits and nodes on the periphery of the core network communicate amongst each other over a first dedicated wavelength. Optical signals on the first dedicated wavelength are converted to electronic signals which are monitored by the electronic controller in each hybrid switch circuit. Routing in the network is optimized by transmitting lower volume data traffic on the first dedicated wavelength which is typically slower due to optical/electronic signal conversions and which uses more resources. Higher capacity data transfers are achieved by transmitting data on an assigned carrier wavelength over an established flow path among the optical switches of multiple hybrid switch circuits. Based on high and low volume data traffic, the method and apparatus discussed herein advantageously supports direct and indirect optical data transmissions with as few overall intermediate optical-to-electrical or electrical-to-optical conversions as possible.

Distributed laser obstacle awareness system

Abstract: A distributed laser based obstacle awareness system for use on-board an aircraft comprises: a plurality of obstacle detecting sensors disposable at a corresponding plurality of locations of the aircraft for emitting laser energy from the aircraft into a predetermined region of space and for receiving return laser energy from an obstacle in the predetermined region of space; a laser source for emitting a laser beam along an optical path; and a plurality of bistatic optical channels. Each channel comprises a plurality of transmission fiber optic cables and at least one receiver fiber optic cable and extends from the laser source to a corresponding obstacle detecting sensor of the plurality to direct the laser beam from the optical path to its corresponding obstacle detecting sensor of the plurality for emission into the corresponding predetermined region of space; and a light detector. Return laser energy from an obstacle received by any one of the obstacle detecting sensors is propagated through the receiver fiber optic cable of the corresponding optical channel to the light detector for use in detection of the obstacle in the corresponding predetermined region of space. In one embodiment, an optical switch is disposed in the optical path to redirect the laser beam in a time sequence manner from the optical path to selected optical channels of the plurality.

Versatile optical code-based MPLS for circuit, burst, and packet switchings

Abstract: We will present versatile optical code (OC)-based photonic MPLS, so-called OC-MPLS which ranges from circuit switching, burst switching, to packet switching. OC-label is an identifier attached to the data, of which information is mapped onto an optical code, a sequence of optical pulses. The OC-label recognition is performed by the optical correlation between an incoming OC-label and the OC-label entries. Unique to the OC-label processing is that it is analog operation entirely in optical domain, and no optical logic operation is involved, therefore, the processing speed is only limited by the propagation delay in the optical correlator, which is a passive optical device. This is a key to the ultrahigh-speed processing capability. Circuit switching of OC-label switched path (OC-LSP) is characterized by the finer data granularity than the wavelength path of GMPS, resulting in a better bandwidth efficiency. In a one-way reservation protocol of photonic burst switching, the OC-labeled control packet improves the throughput by nearly cutting the offset time between the control packet and the following data burst. OC-labeled header of the packet can enables the ultrafast routing in photonic packet switching. To exploit the ultrafast routing capability, a new packet switch architecture is investigated, in which the longest-prefix match algorithm as well as WDM buffering into the fiber delay lines are introduced.

Bi-directional optical transmission system, and master and slave stations used therefor

Abstract: An object of the present invention is to provide a bi-directional optical transmission system wherein a single optical fiber is shared by upstream and downstream systems, thereby eliminating the need for providing an additional optical fiber and reducing the number of maintenance operations. A master station (400) for outputting a downstream optical signal is connected via an optical transmission path (200) to slave stations (500a-500c) each for outputting an upstream optical signal. The optical transmission path (200) includes a single optical fiber connecting at one end to the master station (400), and optical branching units (202a, 202b) branching the single optical fiber for connection to the slave stations. The master station (400) includes an optical passive unit (405) which supplies an upstream optical signal coming through the single optical fiber only to an optical-electrical converter (404) and supplies a downstream optical signal output from an electrical-optical converter (403) only to the single optical fiber. Each slave station includes an optical passive unit (505) which supplies a downstream optical signal coming through the single optical fiber only to an optical-electrical converter (504) and supplies an upstream optical signal output from an electrical-optical converter (503) only to the single optical fiber.

Experimental investigation of quantum key distribution through transparent optical switch elements

Abstract: Quantum key distribution (QKD) enables unconditional physical layer security for the distribution of cryptographic key material. However, most experimental demonstrations have relied on simple point-to-point optical links. In this paper we investigate the compatibility of QKD with reconfigurable optical networks. By performing the first tests of QKD transmission through optical switches, we study if there are impairment mechanisms other than switch insertion loss that impact the sifted and error corrected secret bit yield. Three types of transparent optical switch elements are investigated including lithium niobate (LiNbO/sub 3/), microelectromechanical systems (MEMS), and optomechanical. We show that QKD can be extended beyond point-to-point links to switched multinode architectures including protected ring networks to enhance quantum channel availability.

Three-dimensional MEMS photonic cross-connect switch design and performance

Abstract: Photonic cross-connects (PXC) play a key role in all-optical transparent networks. In this paper, the optical design and modeling of a three-dimensional microelectromechanical system (3-D MEMS) based optical switch are discussed. Basic design rules and considerations are reviewed and used to determine the optimum configuration for free-space optical switches with more than 300 ports. The optical performance of a 256 /spl times/ 256 PXC system, including a 347 /spl times/ 347 nonblocking core switch and auxiliary 2 /spl times/ 2 optical switches for 1:1 protection and optical taps for power monitoring, is presented. The core switch has 1.4-dB median insertion loss, 1.5-dB wavelength dependent loss across a broadband of 1260-1625 nm, and a typical polarization dependent loss of 0.1 dB. Environmental tests including temperature and vibration are described.

Phase dynamics of semiconductor optical amplifiers at 10-40 GHz

Abstract: The phase dynamics that occur in bulk InGaAsP-InP semiconductor optical amplifiers (SOAs) in response to picosecond pulse excitations at 10 and 40 GHz are studied experimentally and numerically for various amplifier lengths. The time dependencies of the phase changes and of the absolute gain of the amplifier are measured simultaneously. The total phase shifts induced by 1.5-ps pulses at 10 GHz are higher than /spl pi/ in SOAs with active region lengths between 0.5 and 2 mm and exceed 2/spl pi/ in a 1.5-mm-long amplifier. Phase shifts above /spl pi/ are measured at 40 GHz in 1.5- and 2-mm-long SOAs. The dependence of the total phase shift on the amplifier bias current and length and on pump pulse energy is investigated. Numerical simulations based on a comprehensive time-domain SOA model allow us to confirm the experimental results for a wide range of amplifier parameters. In particular, SOAs with lengths up to 5 mm have been modeled, and the calculations suggest that the maximum phase shifts occur in amplifiers of approximately 2-mm length. The phase dynamics measurements are illustrated at the example of an optical time division multiplexing add-drop multiplexer, based on a SLALOM switch, gated by 10- or 40-GHz control pulses. We find that simultaneous good dropping and clearing is possible if the length and the operating conditions of the SOA in the switch are chosen such as to induce a full /spl pi/ phase shift.

Optical switching element and photoaddressable display medium using the same

Abstract: An optical switching element including at least a multi-layered optical switching layer that includes a charge generation layer and a charge transport layer wherein, the charge transport layer contains a charge transporting material represented by the following general formula (1). The optical switching element is applicable in a device, a photoaddressable display medium and a display device. The optical switching element may alternatively include a mono-layered optical switching layer that has a charge generating function and a charge transporting function, wherein the mono-layered optical switching layer contains the charge transporting material represented by the following general formula (1).