Showing papers on "Optical switch published in 2000"

Universal relations for coupling of optical power between microresonators and dielectric waveguides

Abstract: The most basic and generic configuration, which consists of a unidirectional coupling between a ring resonator and a waveguide, is considered. The fundamental working equations required to describe the associated power transfer are derived and the application of this geometry to a variety of optical phenomena is discussed. These phenomena include 'add/dropping' of optical beams, add/drop filtering and optical power switching.

Optical interconnects to silicon

Abstract: This paper gives a brief historical summary of the development of the field of optical interconnects to silicon integrated circuits. It starts from roots in early optical switching phenomena, proceeds through novel semiconductor and quantum well optical and optoelectronic physics and devices, first proposals for optical interconnects, and optical computing and photonic switching demonstrators, to hybrid integrations of optoelectronic and silicon circuits that may solve basic scaling and other problems for interconnections in future information processing and switching machines.

Approaches to optical Internet packet switching

Abstract: Wavelength-division multiplexing is currently being deployed in telecommunications networks in order to satisfy the increased demand for capacity brought about by the explosion in Internet use. The most widely accepted network evolution prediction is via an extension of these initial predominantly point-to-point deployments, with limited system functionalities, into highly interconnected networks supporting circuit-switched paths. While current applications of WDM focus on relatively static usage of individual wavelength channels, optical switching technologies enable fast dynamic allocation of WDM channels. The challenge involves combining the advantages of these relatively coarse-grained WDM techniques with emerging optical switching capabilities to yield a high-throughput optical platform directly underpinning next-generation networks. One alternative longer-term strategy for network evolution employs optical packet switching, providing greater flexibility, functionality, and granularity. This article reviews progress on the definition of optical packet switching and routing networks capable of providing end-to-end optical paths and/or connectionless transport. To date the approaches proposed predominantly use fixed-duration optical packets with lower-bit-rate headers to facilitate processing at the network-node interfaces. Thus, the major advances toward the goal of developing an extensive optical packet-switched layer employing fixed-length packets are summarized, but initial concepts on the support of variable-length IP-like optical packets are also introduced. Particular strategies implementing the crucial optical buffering function at the switching nodes are described, motivated by the network functionalities required within the optical packet layer.

Resonant optical nonlinearities in semiconductors

Abstract: Semiconductors provide some of the most promising materials for nonlinear optics, because of large resonant nonlinearities, control of recombination time (from milliseconds to femtoseconds), well-developed fabrication technologies, and compatibility with other optoelectronic devices. The paper reviews some of the concepts and results that have come from the study of nonlinear optics in semiconductors. The emphasis is on nonlinear absorption and the refractive index that arises from the photo-induced excitation of free carriers. Mechanisms described include state-filling, carrier transport, and photorefractivity. Devices include optical bistability, reflective asymmetric Fabry-Perot all-optical absorptive switches, optically addressed spatial light modulators, and real-time holography. The paper's approach is to provide a basic engineering understanding of the principles, some of the historical details, and a snapshot of the state of the field today.

Ultrafast all-optical switching in a silicon-based photonic crystal

Abstract: We study the effect of two-photon absorption and Kerr nonlinearity on the optical properties of a one-dimensional photonic crystal made with amorphous silicon and SiO2. A stop band appearing near 1.5 μm is monitored with a weak probe beam and modulated by changes in the refractive index caused by a pump pulse at 1.71 μm with 18 GW/cm2 peak intensity. Nonlinear optical characterization of the sample using Z-scan points out to two-photon absorption as the main contributor to free carrier excitation in silicon at that power level. Modulation in the transmittance near the band edge is found to be dominated by the optical Kerr effect within the pulse overlap (∼400 fs) whereas free carrier index changes are observed for 12 ps.

Metallic photonic crystals at optical wavelengths

Abstract: We theoretically study three-dimensional metallic photonic-band-gap ~PBG! materials at near-infrared and optical wavelengths. Our main objective is to find the importance of absorption in the metal and the suitability of observing photonic band gaps in this structure. For that reason, we study simple cubic structures and the metallic scatterers are either cubes or interconnected metallic rods. Several different metals have been studied ~aluminum, gold, copper, and silver!. Copper gives the smallest absorption and aluminum is more absorptive. The isolated metallic cubes are less lossy than the connected rod structures. The calculations suggest that isolated copper scatterers are very attractive candidates for the fabrication of photonic crystals at the optical wavelengths. There has been growing interest in the development of easily fabricated photonic-band-gap ~PBG! materials operating at the optical frequencies; 1 these are periodic dielectric materials exhibiting frequency regions where electromagnetic ~EM! waves cannot propagate. The reason for the interest in PBG materials arises from the possible applications of those materials in several scientific and technical areas such as filters, waveguides, optical switches, cavities, design of more efficient lasers, etc. 1 Most of the research effort has been concentrated on the development of two-dimensional and three-dimensional PBG materials consisting of positive and frequency-independent dielectrics 1 because, in that case, one can neglect the possible problems related to the absorption.

Architectural considerations for photonic IP router based upon optical code correlation

Abstract: A photonic label switching router (PLSR) of which the photonic label processing is based upon optical code correlation, is investigated. To resolve the electronic router's bottleneck in current Internet protocol (IP) over wavelength division multiplexing (WDM) networks, we will envision IP over photonic networks in which the PLSRs totally replace the electronic routers. The architectures of PLSR including the photonic label processing, the photonic label swapping, and the optical switching and their optical implementations are studied. Results of proof-of-concept experiments for the photonic label processing and photonic label swapping will confirm the feasibility to attain the target performance: the throughput of 100 Tb/s at least, the processing speed around 10 Gpacket/s, and the number of label entries up to 10 k.

Optical layer survivability-an implementation perspective

Abstract: This paper looks at several aspects of optical layer protection techniques from an implementation perspective. We discuss the factors that affect the complexity of optical protection schemes, such as supporting mesh instead of ring protection, handling low-priority traffic, and dealing with multiple types of failures. The paper also looks at how the client layer interacts with the optical layer with respect to protection, in terms of how client connections are mapped into the optical layer, and how protection schemes in both layers can work together in efficient ways. Finally, we describe several interesting optical protection implementations, focusing on the ones that are different from conventional SONET-like implementations.

20 Gb/s all-optical XOR with UNI gate

Abstract: All-optical Boolean XOR is demonstrated on a 20 Gb/s pseudodata pattern using a semiconductor optical amplifier-based ultrafast nonlinear interferometer (UNI) switch. Bit pattern switching with low-pattern dependence and low switching energies is achieved.

Coherence switching in a four-level system: quantum switching

Abstract: Dark resonance switching among three-laser interactions in a four-level system is observed by using an enhanced nondegenerate four-wave mixing technique. This coherence switching mechanism is based on simultaneous suppression and enhancement of two-photon absorption and has a novel application to high-speed optical switches.

Holographic optical switching: the "ROSES" demonstrator

Abstract: The design, assembly, and performance of a prototype 1/spl times/8 free-space switch demonstrator using reconfigurable holograms are reported. Central to the switch fabric is a ferroelectric liquid crystal (FLC) on silicon spatial light modulator (SLM) deposited with a 540/spl times/1 array of highly reflective and planar mirror strips. The input and output ports of the switch are fabricated as a linear array of silica planar waveguides connected to single-mode fibers, and the holographic beam-steerer operates without the need for adjustment or dynamic alignment. The waveguide array and the single Fourier transform lens for the 2f holographic replay system are housed in an opto-mechanical mount to provide stability. The switch operates at 1.55 /spl mu/m wavelength and has a designed optical bandwidth of >60 nm. The first measured insertion loss and crosstalk figures are 16.9 dB and -19.1 dB, respectively. Improvements in SLM performance, the use of new addressing schemes and the introduction of better alignment techniques are expected to improve these figures considerably. The preliminary performance of a 3/spl times/3 optical crossconnect is also presented to show that this technology is scalable to N/spl times/N switching fabrics.

Non-blocking, scalable optical router architecture and method for routing optical traffic

Abstract: A system and method for providing non-blocking routing of optical data through a telecommunications router that allows full utilization of available capacity. The router includes a number of data links that carry optical data packets to and from an optical router. The optical router includes a number of ingress edge units coupled to an optical switch core coupled further to a number of egress edge units. The ingress edge units receive the optical data packets from the data links and aggregate the optical data packets into “super packets” where each super packet is to be routed to a particular destination egress edge unit. The super packets are sent from the ingress edge units to an optical switch fabric within the optical switch core that routes each super packet through the optical switch fabric to the super packet's particular destination egress edge unit in a non-blocking manner (i.e., without contention or data loss through the optical switch fabric). This routing is managed by a core controller that monitors flow information at each ingress edge unit to control the super packet generation and transmission to the optical switch fabric and schedules each super packet to exit the optical switch fabric so as to avoid contention among the plurality of super packets in the transmission between the optical switch fabric and the egress edge units. The egress edge units receive the super packets, de-aggregate the super packets into the original optical data packets, and transmit the optical data packets to the data lines.

Packet loss in a bufferless optical WDM switch employing shared tunable wavelength converters

Abstract: We propose an architecture for a bufferless packet optical switch employing the wavelength dimension for contention resolution. The optical packet switch is equipped with tunable wavelength converters shared among the input lines. An analytical model Is proposed in order to determine the number of converters needed to satisfy prefixed packet loss probability constraints. This analytical model very accurately fits with simulations results. A sensitivity analysis of the required number of converters as a function of the main system parameters (number of input and output lines, number of wavelengths, ...) and traffic parameters has been carried out. Making use of the introduced dimensioning procedure we have observed that the proposed architecture allows a saving in terms of employed number of converters with respect to the other architectures proposed in literature. Such a saving can reach about 95% of the number of converters.

Demultiplexing of 168-Gb/s data pulses with a hybrid-integrated symmetric Mach-Zehnder all-optical switch

Abstract: We have developed a hybrid-integrated symmetric Mach-Zehnder all-optical switch and evaluated the demultiplexing of 168-Gb/s data pulses at a repetition rate of 10 GHz with this switch. A compact, stable device was realized by assembling semiconductor optical amplifiers as nonlinear waveguides on a planar lightwave circuit in a self-aligned manner. A 6.0-ps switching window needed for 168-Gb/s demultiplexing was provided by the push-pull operation of the symmetric Mach-Zehnder all-optical switch. Demultiplexed signal light showed a high extinction ratio of better than 18 dB. Error-free demultiplexing with a bit error rate of 10/sup -11/ was achieved.

All-optical wavelength converter and switch based on electromagnetically induced transparency

Abstract: We propose a method for all-optical switching and wavelength conversion using electromagnetically induced transparency (EIT). We discuss the mechanism for the transfer of information in this scheme and determine the conditions for which N×N wavelength conversion can be realized. We compare the properties and limits of an EIT-based switch to conventional wavelength converters.

Burst optical deflection routing protocol for wavelength routing WDM networks

Abstract: Given the significant progress made and the continuing advances expected in the optical networking technology, it becomes attractive to build a future Optical Internet that natively supports bursty IP datagrams. Burst switching WDM optical networks are touted as suitable network architectures for future Optical Internet backbones. However, the lack of optical processing capabilities results in increased burst blocking probability, which in turn leads to very limited network performance. Efficient contention resolution method is therefore necessary. Based on discussions of the state of the art of recent optical technologies, a burst optical deflection routing protocol is proposed. The idea of this approach is to use idle optical links as fiber delay lines for contention resolution. Simulation results show that the proposed protocol is available solution for effectively reducing the blocking probability and increasing the performance of burst switching WDM optical networks.

Analysis of a packet switch with memories running slower than the line-rate

Abstract: Our work is motivated by the desire to build a very high speed packet switch with extremely high line-rates. In this paper, we consider building a packet switch from multiple, lower speed packet switches operating independently and in parallel. In particular, we consider a (perhaps obvious) parallel packet switch (PPS) architecture in which arriving traffic is demultiplexed over k identical, lower speed packet-switches, switched to the correct output port, then recombined (multiplexed) before departing from the system. Essentially, the packet switch performs packet-by-packet load-balancing, or "inverse-multiplexing" over multiple independent packet switches. Each lower-speed packet switch, operates at a fraction of the line-rate, R; for example, if each packet switch operates at rate R/k no memory buffers are required to operate at the full line-rate of the system. Ideally, a PPS would share the benefits of an output-queued switch; i.e. the delay of individual packets could be precisely controlled, allowing the provision of guaranteed qualities of service. In this paper, we ask the question: Is it possible for a PPS to precisely emulate the behavior of an output-queued packet-switch with the same capacity and with the same number of ports? The main result of this paper is that it is theoretically possible for a PPS to emulate a FCFS (first come first served) output-queued packet-switch if each layer operates at a rate of approximately 2R/k. This simple result is analogous to Clos theorem for a three-stage circuit switch to be strictly non-blocking. We further show that the PPS can emulate any QoS queueing discipline if each layer operates at a rate of approximately 3R/k.

On the expandability of free-space micromachined optical cross connects

Abstract: Free-space micromachined optical-switching technology has emerged as a promising candidate for the large-scale optical cross connects that are needed in next-generation optical-transport networks. Although this technology has demonstrated good optical performance, its ability to expand to the required port-count while remaining within reasonable optical loss budgets has yet to be demonstrated. In this paper, we theoretically analyze the expandability of free-space micromachined optical switches. The chief loss mechanisms-Gaussian-beam divergence and angular misalignment-are analyzed both theoretically and experimentally. We find that micromirror angular repeatability in such a cross connect must be accurate within about 0.1/spl deg/, and show that integrated mechanical structures are capable of achieving this goal. These results in general suggest that free-space micromachined optical-switching technology appears capable of achieving the port-count required by core-transport networks while remaining within cross-office optical-loss budgets.

Integrated optoelectronic device, and integrated circuit device

Abstract: An integrated optoelectronic device includes an electric circuit unit, such as a bare chip of integrated electronic devices, and an optical device unit for performing at least a portion of the input and output of signals to and from the electronic circuit unit via optical signals. The electronic circuit unit and the optical device unit are packaged in a common package with contoured upper, lower and side surfaces, and the optical device unit is provided on a side surface of the package.

Switch for optical signals

Abstract: A cross-connect switch for switching optical signals, in particular, Dense Wavelength Division Multiplexed (DWDM) signals is disclosed. The switch includes a switching matrix for each of the predetermined wavelengths of the DWDM signals. The switching matrices include Micro-Electro-Mechanical (MEM) systems which have optically reflective elements, typically mirrors, arranged in rows and columns for switching an incoming optical signal travelling along a row of such elements to an output port aligned with a column of the elements. The switch has input demultiplexers to split an incoming DWDM signal into its component channel wavelengths, each of which is directed to a switching matrix where it is switched to an output port and recombined into an outgoing DWDM signal by a mutliplexer before being transmitted out of the switch. A wavelength-converting switch, connected across the switching matrices, is also included for switching channels between wavelengths. Thus, the switch provides port switching by virtue of the switching matrices and channel switching by virtue of the wavelength--converting switch, as well as a combination of both port and channel switching.

Reconfigurable and scalable intergrated optic waveguide add/drop multiplexing element using micro-opto-electro-mechanical systems and methods of fabricating thereof

Abstract: Over the last several years, the rapidly increasing traffic volume carried by telecommunication networks has been clearly observed as a result of the bandwidth-intensive applications such as Internet access, electronic commerce, multimedia applications, and distributed computing. Optical telecommunication systems employing optical fibers as the transmission medium have exhibited a superior performance/cost ratio for both long-haul and short-haul routes and the emerging dense wavelength division multiplexing (DWDM)/all-optical networks have shown some promising potentials. However there still exists a need to improve speed, capacity and connectivity of optical telecommunication networks, as the information system's subscriber growth increases unrestrained. The present invention provides a reconfigurable and scalable fiber optic switching for optical telecommunication networks by integrating MEMS actuators and PLCs for optical signal switching and routing. The integrated optic waveguide switches and optical cross-connect networks are particularly applicable for DWDM/all-optical networks due to its low cost, small crosstalk, reliable, compact, reconfigurable, modular, scalable, and wavelength/polarization insensitive characteristics. The integrated optic waveguide switch can be configured into a variety of all-optical network component such as Add/Drop switch, optical cross-connect switch array, and Add/Drop DWDM filter by combining MEMS actuators and PLC networks into an integrated hybrid microsystem: Micro-Opto-Electro-Mechanical System (MOEMS).

Encapsulated multi-directional light beam steering device

Abstract: A light beam steering device includes a mirror plate that is mechanically coupled directly (or indirectly) to an optically transmissive substrate by flexures that permit the mirror plate to tilt around a plurality of axes when electrodes are controlled to cause the mirror plate tilting. The optically transmissive substrate is spaced apart from a device substrate so that the mirror plate is between the optically transmissive and device substrates. Electrically conductive electrodes are formed on the device substrate opposite the mirror plate. The direction towards a target of the reflected portion of a light beam that is incident on the mirror plate can be monitored and adjusted using a photodetector array. A plurality of optical (e.g. fiber optic) inputs can direct light to an array of such light beam steering devices, which in turn target a plurality of optical (e.g. fiber optic) outputs. The optical inputs and outputs can be part of the same array, or can be provided in separate arrays, and can be part of an optical switch within an optical network.

Microelectromechanical optical switch and method of manufacture thereof

Abstract: A MEMS-based optical switch (100) having improved characteristics and methods for manufacturing the same are provided. In accordance with one embodiment, an optical switch includes a single comb (122) drive actuator (104) having a deflecting beam structure (124) and a mirror (102) coupled to the actuator. The mirror is capable of being moved between an extended position interposed between waveguide channels (106) and a retracted position apart from the waveguide channels. The actuator applies a force capable of deflecting the beam structure and moving the mirror to one of the extended positions or the retracted position and the beam structure returns the mirror to the other of the extended position or the retracted position in the absence of the application of force.

High density optoelectronic transceiver module

Abstract: A high-density blindmate optoelectronic module is provided. The high-density module is adapted to mount on a removable printed circuit board which is configured to be inserted into a printed circuit board support rack located within a chassis based network element. The high-density module is configured to blindmate with a multi-fiber optical connector mounted within the chassis based network element. The high-density blindmate optoelectronic module is formed of a transceiver mounting block which supports a plurality of connectorized optical sub-assemblies. Each connectorized optical sub-assembly includes a plurality of optical transmitters, optical receivers, or a combination of optical transmitters and optical receivers. The optical transmitters and/or receivers define optical axes that extend through a first side of connectorized optical sub-assemblies. The high-density blindmate optoelectronic module includes circuitry for driving the optical transmitters and processing optical signals received by the optical receivers. An electrical interface is provided for transferring signals between the transceiver module and the removable printed circuit board.

MEMS-based variable optical interference devices

Abstract: We discuss our so-called MARS (mechanical anti-reflection switch) devices, in which the membranes in the first devices have the same thickness and refractive index as an anti-reflection coating. By varying the air gap between odd and even multiples of /spl lambda//4 the reflectivity goes from high to near zero. This can be easily understood since if the air gap is zero it is of anti-reflecting and if it is /spl lambda//4 a high reflector mirror stack is formed, and since in any optical stack the reflectivity at the center wavelength is independent of additions of /spl lambda//2 to any layer. Six devices are described that only require variations on the layer structure of this simple mechanical structure, including changes in refractive index and thickness and additional layers. These are the simple data modulator requiring only on and off states, and the design methodology for trading insertion loss for wavelength range, a linear response device for producing harmonic signals, an attenuator requiring variable reflectivity that is independent of wavelength, a multi-electrode wavelength power equalizer, a gain slope compensator that has variable spectral tilt without attenuation changes, and a display design for operation over the entire visible spectrum.

Optical signal processing using nonlinear distributed feedback structures

Abstract: We analyze the optical signal processing functionality of periodic structures consisting of alternating layers of materials possessing opposite Kerr nonlinearities. By elaborating an analytical model and employing numerical simulations, we explore the performance of proposed passive optical limiters and switches. We prove that the proposed limiters provide true limiting by clamping the transmitted intensity at a level which is independent of the incident intensity. We explore the response of optical switches for signal and pump beams having the same and different frequencies. We describe and quantify the performance of the proposed structures in the realization of all-optical OR gates and optical hard-limiters. In addition, we prove that, for fabrication errors as large as 10%, qualitative device functionality remains, with performance only modestly degraded.

Virtual topology reconfiguration of wavelength-routed optical WDM networks

Abstract: The bandwidth requirements of the Internet are increasing every day and there are newer and more bandwidth-thirsty applications emerging on the horizon. Wavelength division multiplexing (WDM) is the next step towards leveraging the capabilities of the optical fiber, especially for wide-area backbone networks. The ability to switch a signal at intermediate nodes in a WDM network based on their wavelengths is known as wavelength-routing. One of the greatest advantages of using wavelength-routing WDM is the ability to create a virtual topology different from the physical topology of the underlying network. This virtual topology can be reconfigured when necessary, to improve performance. We discuss the previous work done on virtual topology design and also discuss and propose different reconfiguration algorithms applicable under different scenarios.

2D optical switch

Abstract: An array of micromachined mirrors are arranged on a first substrate at the intersections of input and output optical paths and oriented at approximately forty-five degrees to the paths. An array of split-electrodes are arranged on a second substrate above the respective mirrors. Each split electrode includes a first electrode configured to apply an electrostatic force that rotates the mirror approximately ninety degrees into one of the input optical paths to deflect the optical signal along one of the output optical paths, and a second electrode configured to apply an electrostatic force that maintains the mirror position. Stability may be improved by using the first and second electrodes in combination to first actuate the mirror and then balance the forces on the mirror to maintain its position. Reproducibly accurate positioning of the mirrors requires either the use of active positioning control or of mechanical stops.

Multibuffer delay line architectures for efficient contention resolution in optical switching nodes

Abstract: This paper proposes an efficient contention resolution switching architecture which can serve as the basis for all-optical switching nodes. The presented solution builds on fiber delay lines used as temporary optical storage and 2/spl times/2 space photonic switches, a solution principle also known as Quadro or switched delay lines (SDLs). The efficiency of SDLs is fundamentally linked to its storage capacity, i.e., the length of the fiber delay lines, while its cost depends on the number of 2/spl times/2 photonic switches, i.e., the number of stages in the switch. This work presents a solution that makes use of multibuffer fiber delay lines which allow multiple packets to be concurrently stored (propagated) on each line. With a novel switch control, it is shown that this solution increases the total storage capacity and significantly improves switch and network performance, without increasing the number of the 2/spl times/2 switches in the system, i.e., its cost.

Scalable optical cross-connect switch using micromachined mirrors

Abstract: This letter describes a free-space optical fiber cross-connect that uses a pair of micromirror arrays to redirect optical beams from an input-fiber array to an output array. This confocal switch architecture is well suited for simultaneous switching of multiple wavelength channels. We show that confocal switches with low insertion loss, low crosstalk, and large port counts can be implemented with surface-micromachined mirror arrays, and we demonstrate a 2/spl times/2 single-mode (1550 nm) switch configuration with insertion loss of -4.2 dB and crosstalk of -50.5 dB. Our micromirror design has sufficient size and angular deflection for scaling to 32/spl times/32 ports.