Showing papers on "Optical switch published in 2002"

Nanowire ultraviolet photodetectors and optical switches

Abstract: no attention has been given to the photoconducting properties of nanowires despite the exciting possibilities for use in optoelectronic circuits. Here, we show the possibility of creating highly sensitive nanowire switches by exploring the photoconducting properties of individual semiconductor nanowires. The conductivity of the ZnO nanowires is extremely sensitive to ultraviolet light exposure. The light-induced conductivity increase allows us to reversibly switch the nanowires between “OFF” and “ON” states, an optical gating phenomenon analogous to the commonly used electrical gating. [2,3,10]

Polymer-based optical waveguides: Materials, processing, and devices

Abstract: Polymer optical waveguide devices will play a key role in several rapidly developing areas of broadband communications, such as optical networking, metropolitan/access communications, and computing systems due to their easier processibility and integration over inorganic counterparts. The combined advantages also makes them an ideal integration platform where foreign material systems such as YIG (yttrium iron garnet) and lithium niobate, and semiconductor devices such as lasers, detectors, amplifiers, and logic circuits can be inserted into an etched groove in a planar lightwave circuit to enable full amplifier modules or optical add/drop multiplexers on a single substrate. Moreover, the combination of flexibility and toughness in optical polymers makes it suitable for vertical integration to realize 3D and even all-polymer integrated optics. In this review, a survey of suitable optical polymer systems, their processing techniques, and the integrated optical waveguide components and circuits derived from these materials is summarized. The first part is focused on discussing the characteristics of several important classes of optical polymers, such as their refractive index, optical loss, processibility/mechanical properties, and environmental performance. Then, the emphasis is placed on the discussion of several novel passive and active (electro-optic and thermo-optic) polymer systems and versatile processing techniques commonly used for fabricating component devices, such as photoresist-based patterning, direct lithographic patterning, and soft lithography. At the end, a series of compelling polymer optical waveguide devices including optical interconnects, directional couplers, array waveguide grating (AWG) multi/demultiplexers, switches, tunable filters, variable optical attenuators (VOAs), and amplifiers are reviewed. Several integrated planar lightwave circuits, such as tunable optical add/drop multiplexers (OADMs), photonic crystal superprism waveguides, digital optical switches (DOSs) integrated with VOAs, traveling-wave heterojunction phototransistors, and three-dimensionally (3D) integrated optical devices are also highlighted.

Critical coupling and its control in optical waveguide-ring resonator systems

Abstract: The coupling of optical waveguides to ring resonators holds the promise of a new generation of switches (modulators) which employ orders of magnitude smaller switching (modulation) voltages (or control intensities). This requires a means for voltage (or intensity) control of the coupling between the waveguide and the resonator. Schemes for achieving such control are discussed.

Analysis of a dynamically wavelength-routed optical burst switched network architecture

Abstract: The concept of optical burst switching (OBS) aims to allow access to optical bandwidth in dense wavelength division multiplexed (DWDM) networks at fractions of the optical line rate to improve bandwidth utilization efficiency. This paper studies an alternative network architecture combining OBS with dynamic wavelength allocation under fast circuit switching to provide a scalable optical architecture with a guaranteed QoS in the presence of dynamic and bursty traffic loads. In the proposed architecture, all processing and buffering are concentrated at the network edge and bursts are routed over an optical transport core using dynamic wavelength assignment. It is assumed that there are no buffers or wavelength conversion in core nodes and that fast tuneable laser sources are used in the edge routers. This eliminates the forwarding bottleneck of electronic routers in DWDM networks for terabit-per-second throughput and guarantees forwarding with predefined delay at the edge and latency due only to propagation time in the core. The edge burst aggregation mechanisms are evaluated for a range of traffic statistics to identify their impact on the allowable burst lengths, required buffer size and achievable edge delays. Bandwidth utilization and wavelength reuse are introduced as new parameters characterizing the network performance in the case of dynamic wavelength allocation. Based on an analytical model, upper bounds for these parameters are derived to quantify the advantages of wavelength channel reuse, including the influence of the signaling round-trip time required for lightpath reservation. The results allow to quantify the operational gain achievable with fast wavelength switching compared to quasistatic wavelength-routed optical networks and can be applied to the design of future optical network architectures.

Optical switching apparatus

Abstract: An optical switching arrangement is provided with continuously rotating mirros (8, 9, 10) which are preferably micro-machined, each deflecting light from an associated optical input (2, 3, 4), preferably mono-mode optical fibres, towards optical outputs (5, 6, 7) in sequence Further pairs of continuously rotating micro-machined mirrors (11/12, 13/14, 15/16) are each associated with respective optical outputs (5, 6, 7) to stabilise the direction of light that is to be coupled with the optical outputs so that better coupling is achieved The optical switching apparatus provides a faster switching arrangement and lower signal loss

All-optical nonlinear switching in GaAs-AlGaAs microring resonators

Abstract: In this paper, we demonstrate all-optical nonlinear switching in compact GaAs-AlGaAs microring resonators at the 1.55-/spl mu/m wavelength. Switching is accomplished in the pump-and-probe configuration in which the pump-and-probe signals are tuned to different resonance wavelengths of the microring. Refractive index change in the microring due to free carriers generated by two photon absorption is used to switch the probe beam in and out of resonance. Measured transient responses of the pump and probe through the microring show good agreement with theoretical predictions based on nonlinear pump-probe interaction due to two photon absorption.

Switch Circuit and Method of Switching Radio Frequency Signals

Abstract: An RF switch circuit and method for switching RF signals that may be fabricated using common integrated circuit materials such as silicon, particularly using insulating substrate technologies. The RF switch includes switching and shunting transistor groupings to alternatively couple RF input signals to a common RF node, each controlled by a switching control voltage (SW) or its inverse (SW_), which are approximately symmetrical about ground. The transistor groupings each comprise one or more insulating gate FET transistors connected together in a “stacked” series channel configuration, which increases the breakdown voltage across the series connected transistors and improves RF switch compression. A fully integrated RF switch is described including control logic and a negative voltage generator with the RF switch elements. In one embodiment, the fully integrated RF switch includes an oscillator, a charge pump, CMOS logic circuitry, level-shifting and voltage divider circuits, and an RF buffer circuit.

Performance analysis of deflection routing in optical burst-switched networks

Abstract: This paper concerns itself with the performance of deflection routing in optical burst-switched networks based on just-enough-time (JET) signaling. Generally speaking, buffer requirement is not vital for JET-based optical burst switching (OBS). However, if deflection routing is enabled, optical buffers are necessary to solve the insufficient offset time problem. A variant of priority queuing model is proposed to approximate burst loss probability and the results show that the model provides an accurate estimation. We also evaluate the performance of deflection routing in Arpanet-2 topology. Simulation results indicate that deflection routing evidently brings significant blocking performance gain, especially with fewer wavelengths and under lighter load. In addition, we notice that excessive deflection will cause longer end-to-end delay and reduce the blocking performance. Therefore, it is necessary to control the maximum allowed deflection occurrences of a burst.

All-optical XOR gate using semiconductor optical amplifiers without additional input beam

Abstract: The novel design of an all-optical XOR gate by using cross-gain modulation of semiconductor optical amplifiers has been suggested and demonstrated successfully at 10 Gb/s. Boolean AB~ and A~B of the two input signals A and B have been obtained and combined to achieve the all-optical XOR gate. No additional input beam such as a clock signal or continuous wave light is used in this new design, which is required in other all-optical XOR gates.

Highly nonlinear Ge-As-Se and Ge-As-S-Se glasses for all-optical switching

Abstract: We have synthesized Ge-As-Se and Ge-As-S-Se chalcogenide glasses designed to have large optical nonlinearities. Measurements reveal that these glasses offer optical Kerr nonlinearities greater than 500 times that of fused silica and figures of merit for all-optical switching >5 at 1.25 and 1.55 /spl mu/m.

All-optical switching and logic gating with spatial solitons in liquid crystals

Abstract: Using mW light beams to generate spatial solitons in nematic liquid crystals, all-optical switching/logic can be performed on a signal launched in the soliton-induced waveguides. Through the collisional behavior of solitons in a nonlocal medium, the signal can be steered in angle and output position. A power-dependent X junction, AND, and NOR gates are demonstrated.

Micromechanical optical switch

Abstract: An optical switch element is described, which includes a fixed layer disposed outwardly from a substrate and a movable mirror assembly disposed outwardly from the fixed layer. The moveable mirror assembly is operable to move relative to the fixed layer responsive to a voltage applied to the movable mirror assembly. In a particular embodiment, the movable mirror assembly includes an inner strip spaced apart from the fixed layer by a first distance and an outer strip disposed approximately adjacent to the inner strip and spaced apart from the fixed layer by a second distance which is greater than the first distance. The optical transmission of the optical switch element changes depending on the position of the movable mirror assembly.

Digital MEMS for optical switching

Abstract: Over the last few years an amazing amount of interest has emerged for applications of micro electro-mechanical systems (MEMS) in telecommunications. Silicon-based optical MEMS have proven to be the technology of choice for low-cost scalable photonic applications because they allow mass manufacturing of highly accurate miniaturized parts, and use materials with excellent mechanical and electrical properties. Applications include tunable lasers, optical switches, and tunable filters. The use of MEMS for optical switching has turned out to be most attractive since this application could revolutionize fiber optic telecommunications. We discuss the technology, performance, and reliability of 2D MEMS optical switches. We show that this technology meets the scalability, performance, and reliability requirements for important applications in fiber optic networks.

All-optical processing with molecular switches

Abstract: A gradual transition from electrical to optical networks is accompanying the rapid progress of telecommunication technology. The urge for enhanced transmission capacity and speed is dictating this trend. In fact, large volumes of data encoded on optical signals can be transported rapidly over long distances. Their propagation along specific routes across a communication network is ensured by a combination of optical fibers and optoelectronic switches. It is becoming apparent, however, that the interplay between the routing electrical stimulations and the traveling optical signals will not be able to support the terabit-per-second capacities that will be needed in the near future. Electrical inputs cannot handle the immense parallelism potentially possible with optical signals. Operating principles to control optical signals with optical signals must be developed. Molecular and supramolecular switches are promising candidates for the realization of innovative materials for information technology. Binary digits can be encoded in their chemical, electrical, or optical inputs and outputs to execute specific logic functions. We have developed a simple strategy to gate optical signals with optical signals by using a photoactive molecular switch. We have demonstrated that NAND, NOR, and NOT operations can be implemented exclusively with optical inputs and optical outputs coupling from one to three switching elements. Our remarkably simple approach to all-optical switching might lead to the development of a new generation of devices for digital processing and communication technology.

Optical multilayer structure and its production method, optical switching device, and image display

Abstract: An optical multilayer structure such that there is a degree of freedom of selection of constituent materials, quick response is possible even in the visible region, and the reliability of the wiring is high. In the optical mulitlayer structure (1), a first layer (11) formed in contact with a substrate (10) and absorbing light, a gap portion (12) having a variable size causing a light interference phenomenon, and a second layer (13) which is transparent are provided in this order on the substrate (10). The following formula (1) is satisfied where N1 (=n1-i·k1 where n1 is the refractive index, k1 is the extinction coefficient, i is the imaginary unit) is the complex refractive index of the first layer (11), n2 is the refractive index of the second layer (13), and the refractive index of the entrance medium is 1.0. (1)

Microfluidic control for waveguide optical switches, variable attenuators, and other optical devices

Abstract: Devices utilize elements carried by a fluid (4506) in a microchannel (4504) to switch, attenuate, shutter, filter, or phase shift optical signals. In certain embodiments, a microchannel carries a gaseous or liquid slug that interacts with at least a portion of the optical power of an optical signal traveling through a waveguide (4510, 4512). The microchannel may form part of the cladding of the waveguide, part of the core and the cladding, or part of the core only. The microchannel may also have ends or may be configured as a loop or continuous channel. The fluid devices may be self-latching or may be semi-latching. The fluid in the microchannel is moved using e.g., electrocapillarity, differential-pressure electrocapillarity, electrowetting, continuous electrowetting, electrophoresis, electroosmosis, dielectrophoresis, electrohydrodynamic electrohydrodynamic pumping, thermocapillary, thermal expansion, dielectric pumping, and/or variable dielectric pumping.

Method of activating optical communication system, channel increasing/decreasing method, and computer-readable recording medium

Abstract: The invention relates to a method of activating an optical communication system comprising a plurality of optical amplifiers having an optical amplifier, between optical transmission lines in which wavelength-division multiplex optical signals are transmitted. The method comprises steps of: generating a desired slope in a desired wavelength range of a gain wavelength curve of the optical amplifier; adjusting an output of the optical amplifier to a desired output level; performing the above two steps in a plurality of optical repeater stations, the steps being carried out in sequence from the first to the last optical repeater stations; and adjusting a level in each optical signal in the wavelength-division multiplex optical signal so as to have substantially constant optical signal-to-noise ratios in the optical signals to be received. Activating the optical communication system according to this procedure allows proper execution of gain slope compensation, output control, and pre-emphasis control.

Performance evaluation of a new technique for IP support in a WDM optical network: optical composite burst switching (OCBS)

Abstract: The optical composite burst switching (OCBS) technique is proposed to be implemented in an all-optical backbone network to support Internet protocol (LP) traffic. The OCBS is based on two main features. First, several IP packets are assembled in a single macropacket, called burst. Second, the burst contention in an optical switch is handled by means of two techniques, the wavelength dimension and the burst-dropping (BD) technique. Different from traditional optical burst switching, where an entire burst is discarded when all of the output wavelengths are engaged at the arrival instant of the burst, a switch adopting the BD technique discards only the initial part of a burst finding all of the engaged output wavelengths while forwarding the final part of the burst, beginning at the instant in which one wavelength becomes free. The OCBS allows an increase in the switch throughput in terms of number of accepted IP packets because a burst contains a given number of IP packets. We introduce the analytical model that allows us to evaluate the effectiveness of the technique and, in particular, the obtained saving; furthermore, a sensitivity analysis of the saving, with respect to both the optical burst switch parameters and the traffic load, is carried out.

Mach-Zehnder interferometer using photonic band gap crystals

Abstract: A photonic crystal optical switch having a periodic dielectric structure including at least one input waveguide First and second waveguide arms branch from the input waveguide in which the relative optical path lengths of electromagnetic radiation within the arms are controlled by stimuli At least one output waveguide that combines the electromagnetic radiation propagating within the first and second waveguide arms

Multichannel digital transmission in an optical network of communicating molecules.

Abstract: In present telecommunication networks, information transfer relies on the interplay of optical and electrical signals. Data are communicated optically but processed electronically. Methods to maintain the propagating signals solely at the optical level must be developed to overcome the transmission capacities and speed limits imposed by the electronic components. We have demonstrated that molecular switches can be used to gate optical signals in response to optical signals. We have realized a simple optical network consisting of three light sources, one cell containing a solution of three fluorescent molecules, one cell containing a solution of a three-state molecular switch and a detector. The light emitted by the three fluorophores is absorbed by the three states of the molecular switch. Using this simple operating principle, we have shown that multichannel digital transmission can be implemented on an ensemble of communicating molecules relying exclusively on the interplay of optical inputs and optical...

Active reflection and anti-reflection optical switch

Abstract: An active, optical, piezoelectric actuated modulator allows switching between a reflecting state and an anti-reflecting state. The modulator, or switch, is based on the precise controlling of an air gap between a thin film membrane and a substrate. The thin film membrane is deformed by a miniaturized adaptive material, such as electrostrictive or piezoelectric (PZT) material. Maximum optical reflection is realized when the air gap is equal to a multiple of a quarter wavelength of an impinging optical beam, while anti-reflection is achieved when the thickness of the air gap is equal to zero or is different from a multiple of the quarter wavelength of the optical beam.

Tuning the index of a waveguide structure

Abstract: The index of refraction of waveguide structures can be varied by altering carrier concentration. The waveguides preferably comprise semiconductors like silicon that are substantially optically transmissive at certain wavelengths. Variation of the carrier density in these semiconductors may be effectuated by inducing an electric field within the semiconductor for example by apply a voltage to electrodes associated with the semiconductor. Variable control of the index of refraction may be used to implement a variety of functionalites including, but not limited to, tunable waveguide gratings and resonant cavities, switchable couplers, modulators, and optical switches.

100 Gb/s optical time-division multiplexed networks

Abstract: We present ultrafast slotted optical time-division multiplexed networks as a viable means of implementing a highly capable next-generation all-optical packet-switched network. Such a network is capable of providing simple network management, the ability to support variable quality-of-service, self-routing of packets, scalability in the number of users, and the use of digital regeneration, buffering, and encryption. We review all-optical switch and Boolean logic gate implementations using an ultrafast nonlinear interferometers (UNIs) that are capable of stable, pattern-independent operation at speeds in excess of 100 Gb/s. We expand the capability provided by the UNI beyond switching and logic demonstrations to include system-level functions such as packet synchronization, address comparison, and rate conversion. We use these advanced all-optical signal processing capabilities to demonstrate a slotted OTDM multiaccess network testbed operating at 112.5 Gb/s line rates with inherent scalability in the number of users and system line rates. We also report on long-haul propagation of short optical pulses in fiber and all-optical 3R regeneration as a viable cost-effective means of extending the long-haul distance of our OTDM network to distances much greater than 100 km.

Optical MEMS devices based on moving waveguides

Abstract: The paper deals with optical microelectromechanical systems (MEMS), and in particular with optical MEMS based on moving waveguides. After a short overview of this very attractive novel activity, specific technological problems and solutions are discussed. Then the following examples of recent developments based on silica on silicon technology are presented: optical switch, vibration sensor, and optical scanner.

Contention resolution for optical burst switching networks using alternative routing

Abstract: Optical burst switching (OBS) is an approach to building very high capacity routing switches based on optical data paths and electronic control. Therefore, OBS is considered as a viable solution in the high-speed optical Internet backbone. In this paper, we propose an intra-class contention resolution scheme in optical burst switching networks by the enhanced alternative routing algorithm. The blocking probability of the proposed scheme is significantly reduced as compared with the general OBS while the additional delay due to the alternative path is smaller than 10% of the basic offset time.

A generalized framework for analyzing time-space switched optical networks

Abstract: The advances in photonic switching have paved the way for realizing all-optical time switched networks. The current technology of wavelength division multiplexing (WDM) offers bandwidth granularity that matches peak electronic transmission speed by dividing the fiber bandwidth into multiple wavelengths. However, the bandwidth of a single wavelength is too large for certain traffic. Time division multiplexing (TDM) allows multiple traffic streams to share the bandwidth of a wavelength efficiently. While introducing wavelength converters and time slot interchangers to improve network blocking performance, it is often of interest to know the incremental benefits offered by every additional stage of switching. As all-optical networks in the future are expected to employ heterogeneous switching architectures, it is necessary to have a generalized network model that allows the study of such networks under a unified framework. A network model, called the trunk switched network (TSN), is proposed to facilitate the modeling and analysis of such networks. An analytical model for evaluating the blocking performance of a class of TSNs is also developed. With the proposed framework, it is shown that a significant performance improvement can be obtained with a time-space switch with no wavelength conversion in multiwavelength TDM switched networks. The framework is also extended to analyze the blocking performance of multicast tree establishment in optical networks. To the best of our knowledge, this is the first work that provides an analytical model for evaluating the blocking performance for tree establishment in an optical network. The analytical model allows a comparison between the performance of various multicast tree construction algorithms and the effects of different switch architectures.

Conformal grating electromechanical system (GEMS) for high-speed digital light modulation

Abstract: A diffractive optical MEMS device for spatial and temporal light modulation is described that is capable of high-speed digital operation. The device contains electromechanical ribbons suspended flat above a silicon substrate by a periodic series of intermediate supports. When actuated electrostatically, the ribbons conform around the support substructure to produce a grating. The device has optical switching times of less than 50 nsec, sub-nanosecond jitter, high optical contrast and efficiency, and reliable actuation in contact mode. The fine gray levels needed for digital imaging systems are produced by pulse width modulation.

Micro-electromechanical optical switch assembly for optical data networks

Abstract: A micro-electromechanical optical switch assembly is provided for an optical network. The switch assembly includes arrays of input and output optical fibers and optical components for selecting light paths that connect any selected pair of input and output fibers. The optical components include optical switching elements, such as torsionally supported micromechanical mirrors that are electrostatically actuated to rotate to direct the light beam along the desired light path. The mirrors are bulk micromachined into a semiconductor wafer, preserving their optical qualities, and formed into a chip mated to a cover. The package incorporates alignment elements to ensure correct position and orientation of the optical components in the package.