Showing papers on "Optical switch published in 1994"

Optical limiting and switching of ultrashort pulses in nonlinear photonic band gap materials.

Abstract: We numerically investigate nonlinear propagation of ultrashort pulses in a one-dimensional photonic band gap structure. We find that, near the band edge, nonlinear effects cause a dynamical shift in the location of the band gap. We demonstrate that this nonlinear mechanism can induce intensity-dependent pulse transmission and reflections. In addition, pulse reshaping and pulse generation is observed. This phenomenon has important new applications in both optical limiting and optical switching.

Network performance and integrity enhancement with optical path layer technologies

Abstract: Path layer technologies will play a key role in the development of a powerful and failure resilient B-ISDN. So far, they have been based on electrical technologies. This paper highlights WDM/FDM techniques and demonstrates that optical paths can greatly enhance the path layer capability and, therefore, the network performance. It is also shown that effective network failure restoration can be achieved with optical paths. The applicability of the wavelength path (WP) technique to global area networks is revealed by comparing different optical path realization techniques. WPs are applied to the national backbone network example to evaluate the required number of wavelengths, and to identify optical cross-connect node requirements. It then proposes a new optical path concept: the virtual wavelength path (VWP). In the VWP scheme, wavelengths are assigned on a link-by-link basis. In other words, the wavelength assigned to a wavelength path has only local significance. Significant benefits of the VWP such as the simplified path accommodation design within a transmission facility network and the reduced number of wavelengths needed, are elucidated. An optical cross-connect node architecture that enables the VWPs is also proposed. The architecture allows the VWP concept to be realized with commercially available optical technologies. The optical path layer concept proposed exploits and consolidates the layered transport network architecture and optical technologies, and will open up new opportunities for creating a B-ISDN that is bandwidth abundant and has a high degree of integrity. >

Femtosecond laser excitation of the semiconductor‐metal phase transition in VO2

Abstract: We have measured the subpicosecond optical response of a solid‐state, semiconductor‐to‐metal phase transition excited by femtosecond laser pulses. We have determined the dynamic response of the complex refractive index of VO2 thin films by making pump‐probe optical transmission and reflection measurements at 780 nm. The phase transition was found to be largely prompt with the optical properties of the high‐temperature metallic state being attained within 5 ps. The ultrafast change in complex refractive index enables ultrafast optical switching devices in VO2.

Some principles for designing a wide-area optical network

Abstract: Explores design principles for next generation optical wide-area networks, employing wavelength-division multiplexing (WDM), and targeted to nationwide coverage. This almost-all-optical network will exploit wavelength multiplexers and optical switches in routing nodes, so that arbitrary virtual topologies may be imbedded on a given physical network. The virtual topology, which is packet switched and which consists of a set of all-optical lightpaths, is set up to exploit the relative strengths of both optics and electronics viz. packets of information are carried by the virtual topology "as far as possible" in the optical domain, but packet forwarding from lightpath to lightpath is performed via electronic switching, whenever required. Algorithms are developed so that the WDM-based network architecture will (a) provide a high aggregate system capacity due to spatial reuse of wavelengths, and (b) support a large and scalable number of users, given a limited number of wavelengths. The authors illustrate their approaches by employing experimental traffic statistics collected from NSFNET. >

Spatial Light Modulator Technology: Materials, Devices and Applications

Abstract: Nematic liquid crystals physical properties of smectic liquid crystals and novel electro-optic effects nonlinear optical properties of organic structures - fundamentals and applications photorefractive materials multiple quantum well spatial light modulators FLC spatial light modulators the magneto-optic spatial light modulator (MOSLM) charge-transfer-plate membrane-mirror light modulators acousto-optic Bragg cell devices smart pixels - technology and applications to parallel computing SLMs in optical computing display applications of SLMs SLMs for optical switching real-time holoography, innovative adaptive optics and compensated optical processors using spatial light modulators.

An optimal nonblocking multicast virtual circuit switch

Abstract: This paper describes an architecture for a multicast virtual circuit switch using cell recycling. This is the first nonblocking switch architecture that is optimal in both the switching network complexity and the amount of memory required for routing cells in multicast virtual circuits. Furthermore, it is optimal in the amount of effort required for multicast virtual circuit modification. This architecture makes it both technically and economically feasible to construct the large switching systems that will ultimately be needed for wide scale deployment of broadband ISDN to residential users. >

Five-stage free-space optical switching network with field-effect transistor self-electro-optic-effect-device smart-pixel arrays.

Abstract: The design, construction, and operational testing of a five-stage, fully interconnected 32 × 16 switching fabric by the use of smart-pixel (2, 1, 1) switching nodes are described. The arrays of switching nodes use monolithically integrated GaAs field-effect transistors, multiple-quantum-well p-i-n detectors, and self-electro-optic-device modulators. Each switching node incorporates 25 field-effect transistors and 17 diodes to realize two differential optical receivers, the 2 × 1 node switching logic, a single-bit node p-i-n control memory, and one differential optical transmitter. The five stages of node arrays are interconnected to form a two-dimensional banyan network by the use of Fourier-plane computer-generated holograms. System input and output are made by two-dimensional fiber-bundle matrices, and the system optical hardware design incorporates frequency-stabilized lasers, pupil-division beam combination, and a hybrid micro-macro lens for fiber-bundle imaging. Optomechanical packaging of the system utilizes modular kinematic component positioning and active thermal control to enable simple rapid assembly. Two preliminary operational experiments are completed. In the first experiment, five stages are operated at 50 Mbits/s with 15 active inputs and outputs. The second experiment attempts to operate two stages of second-generation node arrays at 155 Mbits/s, with eight of the 15 active nodes functioning correctly along the straight switch-routing paths.

All-optical address recognition and self-routing in a 250 Gbit/s packet-switched network

Abstract: The authors report the first demonstration of all-optical address recognition and self-routing of photonic packets for the case where the packet bit period is only 4 ps, corresponding to a 0.25 Tbit/s bandwidth optical network. An ultrafast all-optical device, known as a terahertz optical asymmetric demultiplexer (TOAD), was used to read the address information encoded in a packet header, which in turn was used to route the packet. The bit error rate at the switch output was measured to be less than 10-9.

High-power optically activated solid-state switches

Abstract: Linear photoconductive power switches high-speed switching in photoconductors photoconductive switch-controlled inductive pulsed-power system photoconductive switching using diamond and zinc selenide optically activated opening of copper-doped gallium arsenide switches laser diode arrays for activation of optical switches innovative switching technology the GaAs MESFET as an optically activated switch optically activated travelling wave generators high-voltage lateral switches from silicon or gallium arsenide diagnostic techniques for optically activated solid-state switches III-V-based optoelectronic devices for high-power switching.

Singlemode optical switches based on SOI waveguides with large cross-section

Abstract: The realisation of a thermo-optical Mach-Zehnder interferometer switch based on SOI (silicon-on-insulator) material is reported. At a wavelength of 1.3 mu m, on-off ratios of 13 dB (TE) and 9 dB (TM) are achieved with a switching power of 150 mW. The measured rise time is 5 mu s.

System for wavelength division multiplexing/asynchronous transfer mode switching for network communication

Abstract: The present invention is directed to a system for the wavelength division multiplexing/asynchronous transfer mode (WDM/ATM) operation of high-capacity optical communication networks The optical components of the network can transport vast amounts of information, while the ATM-based electronics provides data processing, and information distribution The capacity of the communications network to reconfigure and rearrange itself is maximized through wavelength translation of its data signals using a limited set of fixed-wavelength channels The system incorporates an optical fiber communication network ring, or several optical fiber communication network rings that are connected to each other, through which data signals are transmitted and received Optical WDM cross-connecting switch devices 4a-4e connect adjacent optical fiber rings 3a, 3b to each other, and control the routing of the data signals into and out of the optical fiber rings 3a, 3b Access node circuits 2a-2d connected to the WDM cross-connecting switch devices 4a-4d can access the data signals in the optical fiber rings 3a, 3b Each of the access node circuits 2a-2d can then route the data signals to individual user stations 5a-5h connected to it A network controller 8 configures the WDM cross-connecting switch devices 4a-4e through their corresponding local node controllers 7

Planar packaging of free-space optical interconnections

Abstract: Planar optics is an approach to build integrated free-space optical systems on single substrates. Computer-aided design, lithographic fabrication, and micro-bonding techniques are used to package the optics in a compact way. This paper reviews recent work on planar optics. It discusses various aspects of the fabrication, the design, and the application of planar optics as an interconnection technology for optoelectronic computing and switching systems. >

Birefringence control of silica waveguides on Si and its application to a polarization-beam splitter/switch

Abstract: A novel polarization-beam splitter/switch with a Mach-Zehnder interferometer configuration was fabricated using a silica-based planar lightwave circuit (PLC) on a silicon substrate. The polarization-beam splitter/switch was realized by accurately controlling the waveguide birefringence and the phase state by laser trimming two kinds of stress-applying amorphous silicon film with widths of 50 /spl mu/m and 95 /spl mu/m. Fiber-waveguide-fiber insertion loss of 0.5 dB and crosstalk attenuations of over 25.6 dB were attained. >

Dynamic switch cascading system.

Abstract: A computer interconnection system provides dynamic switch cascading with a plurality of circuit switches having circuit switch ports coupled by a dynamic connection to provide a dynamically cascadable switching network having a plurality of nodes, including end point and switch nodes. Two individual circuit switches of the network are interconnected by a cross-link group of one or more links. The system transmits frame information including a source endpoint address and a destination endpoint address, each of which can be associated with an endpoint port or a cross-link group, and forms a connection between an endpoint port or a cross-link group to make a connection between a circuit switch port corresponding to a source endpoint address and a circuit switch port corresponding to the destination endpoint. The dynamic circuit switch connections, as applicable to dynamic switch cascade operation, is compatible with the ESCON I/O Interface Architecture or to a fabric node supporting the Class 1 service defined by the Fibre Channel ANSI Standard.

Wavelength division multiplexed multi-frequency optical source and broadband incoherent optical source

Abstract: A wavelength division multiplexing multi-frequency optical source is used to provide downstream transmission of information signals at discrete optical wavelengths from a central office to a plurality of optical network units. A passive optical demultiplexer in a remote node routes the downstream information signals to the optical networks according to optical wavelength. Broadband incoherent sources are used to provide upstream information signals at discrete optical wavelengths which are multiplexed and then routed to the central office for demultiplexing by the passive optical demultiplexer. A wavelength selective coupler in the central office and in each optical network unit combines and segregates downstream and upstream signals of different optical wavelengths for routing to a desired destination.

Free-space digital optical systems

Abstract: Within the past 15 years there has been significant progress in the development of two-dimensional arrays of optical and optoelectronic devices. This progress has, in turn, led to the construction of several free-space digital optical system demonstrators. The first was an optical master-slave flip-flop using Hughes liquid-crystal light valves as optical logic gates and computer-generated holograms as the gate-to-gate interconnects. This was demonstrated at USC in 1984. Since then there have been numerous demonstrations of free-space digital optical systems including a simple optical computing system (1990) and five switching fabrics designated System/sub 1/ (1988), System/sub 2/ (1989), System/sub 3/ (1990), System/sub 4/ (1991) and System/sub 5/ (1993). The main focus of this paper will be to describe the five switching fabric demonstrators constructed by AT&T in Naperville, IL. The paper will begin with an overview of the SEED technology which was the device platform used by the demonstrators. This will be followed by a discussion of the architecture, optics, and optomechanics developed for each of the five demonstrators. >

Apparatus for measuring distortion position of optical fiber

Abstract: An apparatus for measuring a distortion position of an optical fiber is disclosed. A light source generates continuous light with frequency f0 and injects the continuous light into a far-end of an optical fiber to be measured. An optical coupler divides the outgoing continuous light from a near-end of the optical fiber. An optical amplifier amplifies output light from the optical coupler. A first optical switch generates a first optical pulse by switching output light from the optical amplifier. An optical frequency shifter generates a second optical pulse having frequency components (f0 +fm) based on the first optical pulse from the first optical switch. A second optical switch injects the second optical pulse into the near-end of the optical fiber. A display displays outgoing continuous light with frequency f0 from the near-end of the optical fiber via the optical coupler and the second optical switch. A timing control circuit controls the operation timing of the first and second optical switches and the optical frequency shifter.

Novel 1×N and N×N integrated optical switches using self‐imaging multimode GaAs/AlGaAs waveguides

Abstract: We report the demonstration of novel multiway GaAs/AlGaAs electro‐optic waveguide switches which incorporate self‐imaging planar multimode waveguide splitters and recombiners interconnected by single‐mode guides. Each device consists of one or more input guides, a multiway splitter, an array of individually addressed electro‐optic waveguide phase shifters, a multiway recombiner, and an array of output guides. By controlling the voltage applied to the electro‐optic guides, light from any one input guide can be switched to any one output guide. We present experimental results for 1×10 and 10×10 devices. Typical values for switching uniformity, maximum crosstalk, and insertion loss were ±9%, −10 dB, and −12 dB, respectively.

On the number of wavelengths and switches in all-optical networks

Abstract: The authors consider optical networks using wavelength division multiplexing, where the path a signal takes is determined by the network switches, the wavelength of the signal, and the location the signal originated. Therefore, a signal is routed through a combination of circuit switching and wavelength routing (assigning it a wavelength). They present a bound on the minimum number of wavelengths needed based on the connectivity requirements of the users and the number of switching states. In addition, they present a lower bound on the number of switching states in a network using a combination of circuit switching, wavelength routing, and frequency changing. The bounds hold for all networks with switches, wavelength routing, and wavelength changing devices. Several examples are presented including a network with near optimal wavelength re-use. >

A heuristic wavelength assignment algorithm for multihop WDM networks with wavelength routing and wavelength reuse

Abstract: The authors present a heuristic algorithm for effectively assigning a limited number of wavelengths among the access stations of a multihop network wherein the physical medium consists of optical fiber segments which interconnect wavelength-selective optical switches. Such a physical medium permits the limited number of wavelengths to be re-used among the various fiber links, thereby offering very high aggregate capacity. Although the optical connectivity among the access station can be altered by changing the states of the various optical switches, the resulting optical connectivity pattern is constrained by the limitation imposed at the physical level. They also present and study two admission control schemes, used to admit or reject requests for virtual connections. The heuristic is tested on a realistic traffic model, and the call blocking performance of new requests for virtual connections is studied through extensive simulations and compared against the blocking performance of an ideal infinite capacity centralized switch (lowest possible call blocking caused exclusively by congestion on the finite capacity user input/output links, never by the switch fabric itself). Surprisingly, they find that, for a wide range of parameters, the blocking performance of the lightwave network is almost the same as that of the ideal centralized switch. From these results, they conclude that the heuristic algorithm is effective and the admission control scheme is efficient. >

All fiber wavelength selective optical switch

Abstract: An all fiber wavelength selective optical switch has one or more 1xN input optical couplers (20, 120), each having an input signal with a plurality of wavelengths (μ1, μ2, μ3). The output signals from the couplers (20, 120) are connected to fibers (26, 32, 126, 158) having Bragg gratings impressed therein, each having a central reflection wavelength, and each having a tuner attached thereto for detuning a central reflection wavelength of the gratings from a base wavelength corresponding to a wavelength of the input signal. For a given grating to pass a particular wavelength of the input signal that grating must be detuned. The fibers (26, 32, 126, 158) are also connected to one or more Nx1 couplers (66, 98) to combine input signals from different input couplers. The switch allows any combination of input wavelengths from any input signal to be selectively switched to one or more output ports.

1 X N electromechanical optical switch

Abstract: An improved optical switch having a first optical fiber and a plurality of N optical fibers. The first optical fiber forms an optical path with any one of the N optical fibers by an alignment of a longitudinal axis of an end of the first optical fiber with a longitudinal axis of an end of the one of N optical fibers. A switch in optical path is performed by a relative movement of the first optical fiber with respect to the N optical fibers for a realignment of the longitudinal axis of the end of the first optical fiber with a longitudinal axis of an end of another one of the N optical fibers.

Asymmetric optical loop mirror: analysis of an all-optical switch

Abstract: We present an analysis of the optical loop mirror in which a nonlinear optical element is asymmetrically placed in the loop. This analysis provides a general framework for the operation of a recently invented ultrafast all-optical switch known as the terahertz optical asymmetric demultiplexer. We show that a loop with small asymmetry, such as that used in the terahertz optical asymmetric demultiplexer, permits low-power ultrafast all-optical sampling and demultiplexing to be performed with a relatively slow optical nonlinearity. The size of the loop is completely irrelevant to switch operation as long as the required degree of asymmetry is accommodated. This is therefore the first low-power ultrafast all-optical switch that can be integrated on a single substrate.

Analysis of optical crosstalk effects in multi-wavelength switched networks

Abstract: Two optical crosstalk mechanisms, homo- and hetero-wavelength crosstalk, are identified in multi-wavelength switched networks. Homo-wavelength crosstalk does not arise in point-point systems and is a significant factor in multi-wavelength network design. A new signal dependent statistical model was used to evaluate the crosstalk effects due to non-ideal filtering in an established multi-wavelength transport network architecture. The authors find that the optical filters used in this network must have an adjacent channel rejection of /spl ges/20 dB in order to achieve the system design target of 622 Mbit/s channel base rate, at 10/sup /spl minus/10/ BER with 1 dB crosstalk penalty through 10 nodes. >

System and method for dual mode DC-DC power conversion

Abstract: A dual-mode power saving dc-dc converter. The dual-mode power saving dc-dc converter has a first dc-dc converter and a second dc-dc converter. The first dc-dc converter is connected to a first current sensor, and the second dc-dc converter is connected to a second current sensor. The two current sensors are connected to a control logic, which is operable to enable and disable the first and second dc-dc converters. The first dc-dc converter uses less power than the second dc-dc converter. The control logic activates the first dc-dc converter during low current load and activates the second dc-dc converter during high current load. Other systems and methods are disclosed.

Reversal of Ferroelectric Domains by Ultrashort Optical Pulses

Abstract: The response of a soft-phonon ferroelectric material subjected to a high-intensity optical pulse of duration much shorter than the period of the phonon is modeled using a classical, finite-temperature simulation. It is found that complete, permanent reversal of the orientation of the ferroelectric domains may occur even when the energy per atom imparted by the light pulse is much less than the average thermal energy. The result raises the possibility of using the effect to create optical switches or data storage media with switching times less than 10 psec.

Self‐holding photochromic polymer Mach–Zehnder optical switch

Abstract: A self‐holding and optical–optical 2×2 switch using a Mach–Zehnder interferometer with a thermally irreversible photochromic (PC) guest/host polymer cladding is reported. The device was fabricated using a silica‐based integrated optic Mach–Zehnder interferometer with a PC cladding polymer. Cross‐bar switching was achieved by using ultraviolet (313 nm) and visible (≳500 nm) light. The switching state was self‐holding in the dark. Switching was observed with a crosstalk ratio of −12 dB and an excess loss of 7 dB at 1.55 μm.

Hybridized asymmetric fabry-perot quantum well light modulator

Abstract: A device for converting a set of electronic signals that represent an image into a coherent image includes a two-dimensional array (10) of asymmetric Fabry-Perot (ASFP) (100) quantum-well-based optical modulators connected on a pixel-by-pixel basis to a two-dimensional array of drive circuits (150) located on an integrated circuit (160). Electronic signals received by the integrated circuit (160) cause the pixel drive circuits (150) to change a bias voltage applied across the optical modulator (100) section and, thereby, change the optical properties of the optical modulator section (110) of the device. The two-dimensional array can be used to impart intensity-only, phase-only, or phase-and-intensity variations onto a beam of coherent laser light (165) incident on the array. This coherent image can be used with other optical elements to form optical processing machines and optical storage devices.

Optical coupling device

Abstract: PURPOSE: To make it possible to obtain a low-loss coupling characteristics and to realize an optical coupling device improved in producibility by stepwise changing the sizes of the optical waveguide core parts of a spot size changing part and constituting this device CONSTITUTION: This optical coupling device has a core 101 of the optical waveguide, an (n) type semiconductor substrate 102 and an embedded layer or (p) type semiconductor layer 103 The (n) type semiconductor substrate 102 and the (p) type semiconductor layer 103 are formed as the clad region of the optical waveguide The region I is an optical function element part, such as semiconductor laser, optical modulator or optical switch Further, the regions II, III are the optical waveguides having a spot size changing function The light wave spot size of the optical waveguide of the region I is changed gradually stepwise, by which the coupling loss with the optical function device (for example, optical fiber) connected to the light exit end is made small Namely, the optical waveguide is so constituted that at least either of the width or thickness of the core 101 of the optical waveguide is changed stepwise in the diameter size

Self routing exchange and exchange system

Abstract: A self-routing exchange which includes switch modules connected in multiple stages. A synchronous transfer mode (STM) circuit switch module, which is capable of changing over a connection relationship between incoming highways and outgoing highways, is provided between the multistage-connected switch modules and self-routing switch modules. Asynchronous transfer mode (ATM) switch modules are provided as switch modules in preceding and succeeding stages of the circuit switching module. In dependence upon the number m of self-routing switch modules, a controller sets, by means of software, the connection relationship between the incoming and outgoing highways in each of space switches incorporated within the circuit switching module. As a result, the total mn-number of incoming highways from the self-routing switch modules are connected to respective ones of mn-number of outgoing highways set by the controller. In a case where self-routing switch modules are added on later to expand the system, the controller changes the connection relationship between the incoming and outgoing highways in each space switch within the circuit switching module, using software.