Showing papers on "Optical switch published in 1986"

All-silicon active and passive guided-wave components for λ = 1.3 and 1.6 µm

Abstract: End-coupled planar and channel waveguides at 1.3 μm have been demonstrated in single-crystal Si layers grown epitaxially on heavily doped Si substrates, and an optical power divider consisting of intersecting channels was designed and fabricated. Optical switches in Si based on electrooptic, acoustooptic, and optical-injection mechanisms are described. The advantages of all-silicon integrated optical components are discussed.

Architectures for large nonblocking optical space switches

Abstract: This paper introduces three architectures for optical space switches that are based on a multiplicity of fiber interconnected optical components. The architectures eliminate the need for optical waveguide Crossovers and reduce the complexity required in the individual elements. The architectures are strictly nonblocking and allow for easy control and routing. Architecture type 1 exhibits a low system attenuation and a high system signal-to-noise ratio for very large switch dimensions. Architectures 2 and 3 are alternatives for realizing broadcast and point-to-point architectures.

Optically nonlinear waves in thin films

Abstract: A new treatment of the behavior of TE nonlinear waves in an optically nonlinear film is given. The new mathematical results are expressed in terms of the physical parameters of the system and represent a straightforward way to introduce the necessary Jacobian elliptic functions. The optical nonlinearity is of the Kerr type and the numerical calculations are performed for a self-focusing medium. Dispersion curves labeled with optical power density at the lower film boundary, detailed plots of the variation of electric field amplitude as the wave number changes, and details of the power distribution across the guide are given. Since two values of a wave number can exist for the same power level and power thresholds exist, the system is of device interest in the area of optical switching.

A new double‐heterostructure optoelectronic switching device using molecular‐beam epitaxy

Abstract: Two‐terminal switching action is observed in a new optoelectronic device structure. The device has a high‐impedance state without light emission and a low‐impedance state characterized by strong spontaneous emission. The transition from either state to the other may be induced by the appropriate optical or electrical input. It is clear that with the appropriate optical cavity construction the switching device will operate as a laser in the on state rather than in the spontaneous mode reported here. In principle, the device offers large digital optical gain determined by its optical sensitivity and its maximum output power.

Optical bistability, photonic logic, and optical computation.

Abstract: This paper presents new results and reviews the latest state of research in all-optical nonlinear logic switches, amplifiers, and memories. Optical circuit elements that perform the logic functions of the electronic computer are described. Switching speed on a picosecond time scale, the availability of fast high bandwidth consistent communication, and the application of optical parallelism in free space optical wiring are some advantages of the optical computing elements.

Strictly nonblocking 8×8 integrated optical switch matrix

Abstract: We report on a strictly nonlocking 8×8 integrated optics switch matrix in Ti: LiNbO3. The matrix comprises 64 directional couplers on one chip. Insertion losses less than 7 dB have been measured. The extinction ratio has an average value of 30.5 dB for the directional couplers.

New all-optical devices based on third-order nonlinearity of birefringent fibers.

Abstract: Exact solutions for the evolution of the state of polarization along a nonlinear single-mode birefringent fiber are given by means of the Poincare sphere representation. This approach clearly shows the possibility of realizing a new class of devices, namely, a linear coherent amplifier–mixer and an optically activated polarization switch or a phase-sensitive optical discriminator with high fanout.

Ultrafast all-optical gate with subpicosecond on and off response time

Abstract: An all‐optical logic gate consisting of a GaAs‐GaAlAs multiple quantum well structure inserted in a 1.3‐μm‐thick Fabry–Perot cavity is demonstrated to perform with subpicosecond on and off switching time. The use of a purely optical field effect allows for a recovery time as rapid as the switch‐on time.

Integrated quantum well self-electro-optic effect device: 2 × 2 array of optically bistable switches

Abstract: We demonstrate 2×2 arrays of optically bistable devices with very uniform optical characteristics. They are fabricated from an integrated self‐electro‐optic effect device structure consisting of a quantum well p‐i‐n diode grown in series with a load photodiode. Operating power can be optically controlled with a separate beam between ∼40 pW and >470 μW with associated switching times of ∼10 s and <2 μs.

An experiment on high-speed optical time-division switching

Abstract: An experimental high-speed optical time-division switching system has been realized. The system is able to exchange digitally encoded color video signals at 256-Mbit/s highway speed. Bistable laser diodes and directional coupler switch matrices are adopted as optical memories and optical read/write gates, respectively, in an optical time switch. The bistable laser diode operates as an optical flip-flop circuit which can be set and reset by optical and electrical signals, respectively. 256-Mbit/s highway speed has been realized with sufficient input highway operating margin using the same wavelength as that of bistable laser diodes for an electrooptical converter. Results of this experiment will be helpful data for use in constructing future optical telecommunications networks, where a variety of broad-band services need to be realized.

Optical computing: A field in flux

Abstract: The growth and development of the optical computing field is reviewed. The range of aspects explored includes the best materials for electrooptic devices, the circuits that can be built from those devices, the computer architectures that can incorporate those components, and the algorithms that can be run on machines configured for light beams instead of electronic signals. The author considers hybrid computing systems which are close to achieving electronic logic and optical interconnections including reconfigurable optical interconnects. Military applications of analog optical computing are discussed. Research on the optical equivalent of the transistor is described and novel optical computing elements and architectures are considered. Work on neural physiology and psychology is noted which reveals aspects of learning and memory that may be applicable to optical computers. Current worldwide research in materials, devices, algorithms and architectures for optical computing systems is summarized. Differing approaches to research and development are reviewed and contrasted for experts, skeptics, and observers in the field.

Instabilities and all‐optical phase‐controlled switching in a nonlinear directional coherent coupler

Abstract: The instability in the evolution of a nonlinear wave along a directional coupler is investigated with the beam propagation method, both for self‐focusing and for self‐defocusing materials. A new device is proposed for switching an intense light beam at the device output by changing the relative phase of a weak input signal.

Optical bistability in the scattering and absorption of light from nonlinear microparticles

Abstract: Intrinsic optical bistability in the scattering and absorption of light from Rayleigh-particle-sized microparticles having an intensity-dependent refractive index is theoretically investigated. For particles near plasmon resonances optical switching also occurs by sweeping the frequency across the resonance at fixed incident intensity above a certain threshold. Several orders of magnitudes of reduction in the switching intensities are possible near sharp resonances, and an optical transistor mode with a very sizable differential gain can be achieved.

Electrically controlled integrated optical switch

Abstract: An electrically controlled integrated optical switch having a body made up entirely of crystalline silicon. More specifically, the body has a pair of channel waveguides intersecting in an X-like configuration forming therein an intersection crossover region. A first electrode is positioned on the intersection crossover region and a second electrode is positioned on the bottom of the body opposite the intersection crossover region. A controllable current/voltage source is electrically connected to the electrodes in order to alter the index of refraction of the intersection crossover region in order to change the amount of optical cross coupling of light between the intersecting waveguides.

Rotary access arm for optical disks

Abstract: A rotary access arm, e.g. for an optical disk has crossed voice-coil actuators (6a,b) for in-plane and vertical movements, e.g. track and focus control; the actuators are secured to its distal end in close proximity to the focussing optical system (5a,b). The heavy elements like laser light source (8) and beam analyzer (11) are arranged near the rotational axis (10) of the arm (or are completely separated therefrom) allowing a very lightweight construction. In an optical storage system using stacked disks co-axial access arms with individual position control are provided. For increased reliability of operation each access arm has two focussing optical systems at its distal end, viewing in opposite directions, and a bi-stable optical switch (12) to selectively focus the laser beam on one of the two adjacent optical disks. The focussing optical system can be realized with individual lenses or with two conjugate plano-aspheric lenses bonded to a 90° reflection prism.

LiNbO 3 traveling-wave light modulator/switch with an etched groove

Abstract: A Ti dffused lithium niobate traveling-wave interferometric light modulator/switch with a groove excavated at the electrode gap has been fabricated and tested at microwave frequency. The groove suppresses the undesirable light coupling between the two parallel waveguides for the phase shifting section so that the drive voltage is decreased by reducing the separation of the parallel waveguides, or of the electrodes. In addition, the groove decreases the effective index for the modulating wave to reduce the velocity mismatch between light wave and microwave so that the bandwidth is broadened. The modulation experiment was carried out from dc to 15 GHz at 633 nm light wavelength. For the modulator with the electrodes 6 mm long and 10 μm apart, the half-wave or switching voltage was 3 V, the extinction ratio was 18 dB, the 3 dB bandwidth was 12 GHz and a P/\Delta f of 1.5 mW/GHz was obtained.

All-optical switching effects in a passive GaAs/GaAlAs multiple-quantum-well waveguide resonator

Abstract: All-optical switching has been observed in a passive GaAs/GaAlAs MQW waveguide resonator at room temperature, and we have shown that the mechanism responsible for the switch is not due to thermal effects.

Femtojoule optical switching in nonlinear semiconductor laser amplifiers

Abstract: We have demonstrated the operation of an optical switch requiring less than 1 f J (<7000 photons) of incident optical energy. The switch operates at room temperature, is compatible with optical communication systems, and is cascadable because it has gain. The switching times (on and off) are determined to be less than 1 ns. This device significantly advances the possibility for realization of high throughput optical signal processing and digital optical computing.

Optically controlled integrated optical switch

Abstract: An optically controlled integrated optical switch having a body made up of entirely crystalline silicon. More specifically, the body has a pair of channel waveguides intersecting at an X-like configuration forming therein an intersection crossover region. An electrically controlled optical source is positioned over the crossover region to shine intense, short wavelight on the crossover region in order to generate numerous electron-hole pairs in the waveguide material. These charge carriers alter the refractive index of the intersection region. A controllable current source is used to adjust the optical output power of the optical source. This, in turn, changes the amount of optical cross coupling of light between the intersecting waveguides.

Low crosstalk 4 &#215; 4 TiLiNbO 3 optical switch with permanently attached polarization maintaining fiber array

Abstract: Several low crosstalk 4 × 4 crossbar optical switch arrays have been fabricated for use at \lambda = 1.3 \mu m. Each array consists of 16 independently functioning directional coupler switches. We describe the typical device performance characteristics. The average insertion loss is 5.2 dB. Crosstalk levels routinely measured < -35 dB. The voltage required to operate the device is ≈ 13 V. The inputs to one of the device arrays were permanently attached to four laser transmitters using lensed polarization maintaining fiber at the laser end and an array of polarization maintaining fibers at the device end.

InGaAsP/InP monolithic integrated circuit with lasers and an optical switch

Abstract: InGaAs/InP monolithic integrated circuits composed of a compact carrier-injection optical switch and distributed feedback laser diodes are fabricated. These integrated circuits have a variety of functions, such as monolithic modulators, switches and optical amplifiers for optical communication systems.

A Conceptional Design on Optical Frequency-Division-Multiplexing Distribution Systems with Optical Tunable Filters

Abstract: Optical frequency-division-multiplexing distribution systems providing more than ten frequency multiplexed optical signals separated by on the order of gigahertz, distribute signals to plural receivers, where one of the signals is selected by a frequency selection switch (FS-SW). This paper describes the design of an optical frequency-divisionmultiplexing distribution system. Investigation is made of periodic filters for frequency division multiplexers and FS-SW, and the optical source, as well as single-mode fiber polarization mode dispersion. Preliminary transmission experiments using a bit rate of 450 Mbits/s, fiber length of 13 km, and frequency spacing of 11 GHz are also demonstrated at a 1.5 μm wavelength to show the design's suitability.

Three-space representation of phase-mismatch switching in coupled two-state optical systems

Abstract: A three-space graphical representation for the operation of optical switch/modulators based on two-state systems is reviewed. This visual framework provides insight into the behavior of devices such as the waveguide directional coupler and Mach-Zehnder interferometric switches and combiners and the concept of delta-beta reversal. I is based on the covering map of the group SU(2) onto SO(3) and is analogous to the Poincare formulation for polarization. Because of its pictorial nature, this representation can serve as an aid in the conception of innovative device structures. A class of switches identified using this approach is described and demonstrated by experiment.

Multiple field of view sensor

Abstract: Images of two fields of view of one or two scenes in a radiation sensor are generated by use of a single detector and common signal process circuitry. The two imaged fields of view, typically a narrow view and a wide view, are provided by two independent telescopes (18, 20), and are combined by use of a field-of-view switch (32) comprising a chopper wheel (34) or an optical switch in synchronized operation with a mirror scanner (22). The same field-of-view switch is employed in performing detector non-uniformity correction functions, such as automatic responsivity control and direct current restoration. Folding optics couples scanned radiation from the scanner to the switch. An additional field of view may be introduced by displacing a folding mirror of the folding optics. Also, a portion of a reflecting surface of the switch may be tilted to admit a reference beam of radiation useful in performing the functions of responsivity control and D.C. restoration.

Bipolar transistor carrier-injected optical modulator/switch: Proposal and analysis

Abstract: Bipolar transistor structures can be used, instead of conventional p-n (p-i-n) junctions, to realize high-speed optical modulators and switches, which are operated by free-carrier injection. Some basic results obtained by the theoretical analysis of the structure applied to a DH X crossing are presented, with emphasis on the switching speed. It is shown that switching times can be as fast as 60 ps for the required ON-OFF optical switching, which is considerably faster than those expected for a diode structure.

A polarization-independent 1 &#215; 16 guided-wave optical switch integrated on lithium niobate

Abstract: We report the fabrication and testing of several models of a complex integrated Ti : LiNbO 3 switch array, a one-input-to-sixteen-output switch that is polarization independent for use with standard single-mode fibers. The switch array has 15 directional couplers arranged in a binary tree with four ranks. The device is fitted with connectorized single-mode fiber pigtails and housed in a package that permits convenient transport and use. The best measured losses (fiber-waveguide-fiber) are 3.0 dB for the TE polarization and 3.6 dB for the TM. Permanent attachment of the pigtails adds 0.65-dB loss. Crosstalk suppression averages 10 dB below the transmitted signal for the brightest unwanted path.

Tank gauge system

Abstract: A method and apparatus are provided for measuring the level of a surface of a material in a tank. The apparatus and method modulate an optical radiation beam at a radio frequency. The radiation beam is transmitted to the surface and the reflected beam received. The modulation frequency is changed until the phase of the received beam is the same as that from an optical reference path. The optical reference path is any fixed length path that allows the beam to pass from the source of the beam to the receiver that receives the reflected beam. An optical switch determines whether the receiver receives the reflected beam or the reference beam. The change in modulation frequency may then be correlated with the level on the material's surface in the tank.

Directional coupler switches with optical gain

Abstract: We discuss the design and characteristics of directional coupler switches in semiconductor materials (GaAs/GaAlAs) which exhibit optical gain by laser action. Equal gain in the bar and cross states is achieved by carrier-induced changes in the real as the well as the imaginary parts of the refractive index in directional coupler structures. Conditions for equal gain and crosstalk, design tradeoffs, and saturation characteristics in terms of amplified spontaneous emission in relation to saturation power are briefly discussed.

Assessment of switching speed of optical bistability in semiconductor laser amplifiers

Abstract: Measured hysteresis characteristics are presented for a bistable Fabry-Perot laser amplifier operating at high switching rates The results show that optical bistability ceases to be evident at a repetition frequency of around 250 MHz, corresponding to a data rate of 500 Mbit/s, which indicates switching times commensurate with the carrier recombination time

Fiber optic aircraft load relief control system

Abstract: A fiber optic load measuring system is disclosed comprising an optical pulse generator, an optical bus, a plurality of optical pulse routing switches, a plurality of optical attenuators disposed along the surface where the load is to be measured, a plurality of optical pulse routing switches, and a signal processor. The optical attenuators are each connected to a dedicated optical pulse routing switch and are adapted to vary the attenuation of the optical pulse in response to the applied load. The optical pulse routing switches are adapted to selectively direct the optical pulses to individual optical attenuators, such that each of the optical attenuators is separately and sequentially pulsed.