Showing papers on "Optical switch published in 1989"

Lightwave systems with optical amplifiers

Abstract: Fiber-optic communication systems using semiconductor laser amplifiers are investigated theoretically and experimentally. The noise and bit-error-rate characteristics of lightwave systems with optical amplifiers are calculated and the dependence of system performance on amplifier characteristics such as optical bandwidth, noise figure, gain, etc., is shown. Experimental results for both a 4-Gb/s optical preamplifier as well as coherent and direct detection systems with four inline amplifiers are presented. >

Picosecond GaAs‐based photoconductive optoelectronic detectors

Abstract: A novel material deposited by molecular beam epitaxy at low substrate temperatures using Ga and As4 beam fluxes has been used as the active layer for a high‐speed photoconductive optoelectronic switch. The high‐speed photoconductive performance of the material was assessed by fabricating two devices: an Auston switch and a photoconductive‐gap switch with a coplanar transmission line. In a coplanar transmission line configuration, the speed of response is 1.6 ps (full width at half maximum) and the response is 10 to 100 times greater than that of conventional photoconductive switches. Since the material is compatible with GaAs discrete device and integrated circuit technologies, this photoconductive switch may find extensive applications for high‐speed device and circuit testing.

Optical harmonic generation and mixing in multilayer media: analysis using optical transfer matrix techniques

Abstract: Optical harmonic generation from a multilayer sample consisting of an arbitrary number of parallel slabs of arbitrary thicknesses can be treated exactly (in the limit where the nonlinear depletion of the pump beam can be neglected) by using a transfer matrix technique. This approach is described, and the results are given in a computationally convenient form. The technique is illustrated by application to a typical case.

Experimental demonstration of optical soliton switching in an all-fiber nonlinear Sagnac interferometer

Abstract: We demonstrate, for the first time to our knowledge, the switching of optical solitons. We observe switching of 93% of the total reflected energy in a partially transmitting integrated fiber loop mirror that makes up the interferometer. This result demonstrates the potential of solitons as the natural bits in ultrafast optical processing.

Semiconductor optical amplifiers

Abstract: An overview of semiconductor optical amplifier characteristics and their potential applications is presented. The latter consist of nonregenerative repeaters, optical receiver preamplifiers, power amplifiers and amplifier/modulators, general optical gain blocks, narrowband tunable amplifiers, and bistable amplifiers. >

Wavelength division multiplexing light source with integrated quantum well tunable lasers and optical amplifiers

Abstract: We describe a photonic integrated circuit composed of three 1.5 μm wavelength multiple quantum well tunable lasers with a passive optical power combiner and an optical output amplifier. Independent channel operation with 1–2 mW/channel output power is demonstrated.

Optical transitions in a step quantum well

Abstract: We have theoretically studied the field‐dependent optical properties of a step quantum‐well structure, which consists of a small well inside a big well. The wave functions of the small and big wells overlap and their eigenenergies have different field dependencies. The transition from a small‐well state to a big well state thus gives a large Stark shift at low applied field without degrading the oscillator strength. Another advantage is to allow optical transitions that are forbidden in simple single‐well structures. This relaxation of the selection rule makes it possible to provide optical pumping for intersubband lasing. Also, since the step well is asymmetric, many nonlinear properties are expected.

Multiwavelength networks and new approaches to packet switching

Abstract: The author shows how the bandwidth available through the use of multiwavelength optical-fiber technology can be used to achieve novel large-capacity switching systems to address anticipated switching bottlenecks. He does so by describing the features and network applications of a specific multiwavelength network, the Bellcore LAMBDANET packet switch. The discussion is then extended to a number of recent proposals for switching fabrics based on this new multiwavelength technology. The particular technologies he discusses are: the photonic knockout switch, a proposal similar to the concept of the LAMBDANET, but not requiring N receivers at each node; the FOX (fast optical cross-connect), an active wavelength routing approach; the ShuffleNet architecture; the HYPASS and BHYPASS switches; the coherent wavelength division lambda switch; and the Bellcore Star-Track multicast switch. >

Use of femtosecond square pulses to avoid pulse breakup in all-optical switching

Abstract: The authors report measurements of ultrafast all-optical switching in dual-core fiber nonlinear couplers. By performing the measurements with square optical pulses, the pulse breakup which occurs in experiments performed by using conventional bell-shaped pulses is minimized. Compared to measurements performed by using conventional bell-shaped pulses, the measurements yield decreased switching power, a sharper switching transition, and improved power transfer. It is concluded that square pulse switching can be utilized to enhance the switching performance of any ultrafast all-optical switching device triggered by instantaneous intensity. >

Output-buffer switch architecture for asynchronous transfer mode

Abstract: An asynchronous transfer mode (ATM) switch architecture for the broadband integrated services digital network (ISDN) is proposed. The proposed switch, called ATOM switch (ATM output-buffer modular switch), has a multistage network structure, retaining a high degree of modularity for capacity expansion. The ATOM switch element belongs to an output-buffer switch category, and it has a time-division-multiplexed bus and first in, first out buffers for individual outgoing lines. A bit-sliced circuit structure is adopted to implement the high-speed time-division bus and buffer memories. The proposed switch has no throughput degradation because of internal blocking, and has a simple control structure for providing a priority scheme and multicast connections. >

Observation of nonlinear optical transmission and switching phenomena in polydiacetylene-based directional couplers

Abstract: Nonlinear optical transmission and switching phenomena have been observed in directional coupler devices fabricated from soluble polydiacetylenes. Effects due to both slow thermal nonlinearities and ultrafast (picosecond) electronic nonlinearities were identified. At the operating wavelength of 1.06 μm used here, the ultrafast electronic nonlinear phenomena originated from intensity‐dependent changes in the imaginary part of the refractive index due to two‐photon absorption effects.

Effect of two‐photon absorption on all‐optical guided‐wave devices

Abstract: We show that two‐photon absorption can lead to serious deterioration in the all‐optical switching characteristics of nonlinear directional couplers and distributed feedback gratings.

Overlap integral factors in integrated optic modulators and switches

Abstract: Coplanar strip and complementary coplanar strip electrodes are often used in integrated optical switches and modulators using the optical directional coupler. The field analysis of these electrodes is performed to determine the optimum overlap integral between the optical field and the modulating electromagnetic field. The optimal placement of the electrodes with respect to the optical channel waveguides is presented as a function of electrode width and spacing. >

Polymeric optical waveguide switch using the thermooptic effect

Abstract: An all-polymeric optical waveguide switch which uses total internal reflection from a thermally induced index barrier is discussed. Very large effective index changes Delta N=2*10/sup -2/ were found in the polymeric waveguide. The temperature under the evaporated stripe heater was measured from the change in its resistance. The effective index change due to the temperature increase agrees well with values calculated from the deflection angles. The operation of the switch is, apart from a small waveguide dispersion effect, polarization-insensitive. Switching times of about 10 ms were measured. It should be possible to reduce them to a few milliseconds in optimized thermal designs and with regulated power dissipation in the heater. >

Electro-optical analog-to-digital converter and method for digitizing an analog signal

Abstract: An electro-optical analog-to-digital converter having an enhanced effective sample rate. Several embodiments of the electro-optical analog-to-digital converter (10, 100, 150, and 200) are described, each involving either space-division demultiplexing, time-division demultiplexing, or wavelength-division demultiplexing to increase the effective sample rate at which an analog signal provided by a source (36) can be converted to a digital signal using electrical analog-to-digital converters (66). A plurality of light pulses having a constant amplitude are modulated in response to the analog signal and demultiplexed using one of the three different techniques, so that the analog signal is sampled at successive points in time, varying the intensity of light pulses passing through each modulator channel (32, 104). In the space-division demultiplexing approach, light pulses produced by a mode-locked diode laser (12) are split into a plurality of channels and delayed by different time intervals so that the replicated pulses are spaced apart in time prior to being modulated by passage through a modulator array (32). The demultiplexed and modulated light pulses are input to a plurality of photodetectors (56) amplified by a plurality of amplifiers (60 ), and input to a plurality of electrical analog-to-digital converters (64). In the time-division multiplexing approach, either discrete optical switches (108) or an optical switch array (158) is used to transmit successive modulated light pulses into selected photodetectors for conversion to an electrical signal that is input to the analog-to-digital converters. The wavelength-division multiplexing approach uses a plurality of mode-locked diode lasers (210), each having a different characteristic wavelength. Pulses output from the mode-locked diode lasers are generated at different times and provided to a wavelength-division multiplexer (214) where they are combined and input to the modulator. A wavelength-division demultiplexer (220) separates the different wavelength pulses for input to selected photodetectors. For all the embodiments, the effective sample rate corresponds to the number of channels multiplied by the rate at which pulses are produced by the mode-locked laser diodes.

Digital optics

Abstract: The authors discuss digital optics, a technology for processing, transport, and storage of optical digital information. Digital optics offers both the high temporal bandwidth of fiber communications and the high connectivity and information density of optical imaging. The energy dissipation per bit of communicated information, as well as the chip area dedicated to interconnections, can be significantly lower in optics than in high-speed electronics. This motivates the introduction of parallel optical interconnections through free space in communication-intensive areas of digital information processing such as switching in telecommunications and within multiprocessors. Digital optical circuits can be constructed by cascading two-dimensional planar arrays of optical logic gates interconnected in free space. The state of the art and the trends in digital optical information processing systems for optical logic, optoelectronic interfaces, and optical free-space interconnection systems are reviewed. >

Optical switches using ferroelectric liquid crystals

Abstract: This invention comprises a new group of fiber optic switching devices that use layers of surface-established ferroelectric liquid crystals (FLCs) as the switching media. In each of the devices light impinges upon the ferroelectric liquid crystal a an angle of 90 degrees (normal incidence) with the surface plane. Each FLC gives 0 degrees or 90 degree optical rotation, depending upon the polarity of the electric voltage applied. A series of polarizing beam splitters are used to separate unpolarized light into its s and P polarization components. After ferroelectric liquid crystal switching, other polarizing beam splitters are used to direct the s and p light to output optical paths. The switches discussed include voltage controlled 2×2, 1×4, 1×6, 1×8, 4×4 and dual plane devices that use one or more layers of surface stabilized ferroelectric liquid crystals to direct optical signals.

Optical switching in low-dimensional systems

Abstract: The workshop was a part of the NATO Special Program on Condensed Systems of Low Dimensionality (1983-1988). Contributors concentrate on the development and study of optical and electro-optical devices, as well as experimental and theoretical investigations of the underlying optical nonlinearities. T

All‐optical switching in nonlinear X junctions

Abstract: All‐optical switching in nonlinear X junctions with Kerr and saturable nonlinearities is analyzed using the beam propagation method. We establish that switching is possible in the nonlinear X junction, and compare its nonlinear phase shift requirements with that of other all‐optical devices.

Fast linear electro‐optic effect based on cholesteric liquid crystals

Abstract: Flexoelectric effect in cholesteric liquid crystals can be used to produce optical switching on a microsecond time scale. In a simple geometry, this effect produces a light modulation the amplitude of which is linear in field. The switching time from one optical state to the other is predicted to be independent of the magnitude of the electric field. We confirm this prediction experimentally in a room‐temperature cholesteric liquid crystal.

Vertical to surface transmission electrophotonic device with selectable output light channels

Abstract: A photoeletronic bistable device with selectable light output channels has been fabricated for implementation in photonic switching and processing systems. The device is a variation of the vertical to surface transmission electrophotonic device. Output in the stimulated light emission mode was successfully obtained from different waveguide channels by external electronic switching. Output channels could be switched at a rate of 400 Mb/s. The potential versatility of this device has been experimentally confirmed in programmable or switchable optical interconnections.

Novel femtosecond solitons in optical fibers, photonic switching, and computing

Abstract: It is shown that novel (10–20)‐fs solitons can propagate in optical fibers. This theory is expressed in terms of measurable optical fiber parameters, and experimental conditions for observing them are given. This result is general and can apply to many optical problems, such as the following: modulation instability, cross‐phase modulation, pulse compression, amplification by stimulated Raman scattering, higher‐order soliton fragmentation, ultrafast optical switching, fiber‐soliton lasers, soliton‐dye lasers, and optical soliton switches for optical computing.

Optoelectronic technology and lightwave communications systems

Abstract: 1 Optical Fiber Waveguides.- 1. Transmission Properties of Optical Fibers.- 2. Measurement and Characterization of Optical Fibers.- 3. Advanced Single-Mode Fiber Designs for Lightwave Systems Applications.- 4. Polarization-Maintaining Optical Fibers.- 5. Transmission Limitations in Fibers due to Nonlinear Optical Effects.- 2 Fiber-Joining Technology and Passive Optical Components.- 6. Optical Fiber Connectors, Splices, and Jointing Technology.- 7. Passive Components for Optical Coupling and WDM Applications.- 3 Semiconductor Laser Sources and Photodetectors.- 8. Basic Physics of Semiconductor Lasers.- 9. Fabrication and Characterization of Semiconductor Lasers.- 10. Transverse Mode Control in Semiconductor Lasers.- 11. Longitudinal Mode Control in Laser Diodes.- 12. Modulation Properties of Semiconductor Lasers.- 13. High-Power Semiconductor Lasers.- 14. Photodetectors for Long-Wavelength Lightwave Systems.- 4 Optical Transmitters and Receivers.- 15. Semiconductor Laser Transmitters.- 16. Optical Receivers.- 5 Applications of Optoelectronics in Lightwave Systems.- 17. Optical Communications: Single-Mode Optical Fiber Transmission Systems.- 18. Optical Fiber Communication Systems: Local Area Networks.- 19. Future Applications of Optical Fiber Networks.- 20. Free-Space Optical Communication Systems.- 21. Optical Fiber Sensor Technology.- 22. Optoelectronic Information Processing: Laser Bar Code and Laser Printer Systems.- 6 Future Optoelectronic Technology and Transmission Systems.- 23. Optoelectronic Integrated Circuits.- 24. Coherent Optical Fiber Communication Systems-The Promise for the Future.- 7 Impacts on the Information Society.- 25. The Impact of Optoelectronics Technology on the Information Society.

Rotary head actuator for optical disk

Abstract: A rotary actuator for an optical head comprises a pair of reflectors mounted respectively on the end of the arm and on the pivot axis to define an optical path via the arm to an optical disk for an external beam directed along the pivot axis. Special arm geometry reduces variable head skew and consequent image rotation. A multiple platter design features optical switches effectively aligned on the pivot axis.

Liquid crystal optical switching device

Abstract: A pair of transparent trapezoidal prisms each having angled endfaces with the larger bases in juxtaposition with respect to each other forming an interface therebetween are provided with at least one optical input and output coupled to the angled endfaces of the prisms. Optical radiation is applied to the input and normal to the angled endface at an angle greater than the critical angle with respect to the interface between the prisms. A liquid crystal beam splitter is positioned in the interface for splitting the radiation between the prisms each of which has a liquid crystal optical shutter positioned in the respective prisms to receive optical radiation which has been transmitted or reflected from the beam splitter at an angle normal to the optical shutter. Each of the shutters is provided with a variable biasing voltage of a continuous nature which is selectively variable for controlling the radiation passing therethrough thereby forming a controllable optical switch.

Liquid crystal device

Abstract: PURPOSE: To prevent the deterioration of liquid crystal(LC) elements by a simple method by providing the LC device with a mechanism for setting up at least one of plural potential levels to be supplied to the LC elements to earth potential, and in a non-operation period, simultaneously setting up counter electrodes in all LC elements to the earth potential. CONSTITUTION: A control circuit 32 sends a scanning electrode data signal 3 and a scanning electrode control signal 39 to a scanning electrode driving circuit 34 and sends a signal electrode data signal 38 and a signal electrode control signal 40 to a signal electrode driving circuit 35. Scanning electrode power supply circuits 33, 36 for supplying output potential levels u1 to u4 , v1 to v4 are respectively connected to both the driving circuits 33, 36 and control signals 41, 42 are respectively used for switching at least one of four potential levels to the earth potential. When the control signals 41, 42 are sent in a non- printing period, the earth potential is respectively outputted from the circuits 34, 35, all electrodes on an optical switch array 21 are earthed to prevent the deterioration of the LC elements.

Optics and supercomputing

Abstract: Storage, interconnection, and processing are discussed. Various types of optical disks and page-oriented holographic memories are considered. It is shown that optical storage is advancing rapidly and holds the potential of hundreds of megabytes per second data rates from a single storage unit, which can provide many new opportunities for supercomputing. Module-to-module, board-to-board, and chip-to-chip interconnection and gate-to-gate communication are discussed. It is concluded that optical interconnection is, in many cases, superior to electronic interconnection and holds the key to the development of future electrooptic systems. Optical computing devices are discussed and various application areas where optical processing as well as storage and interconnection are expected to play a role in the future are considered. The authors believe that optical processing, while holding considerable promise, lags behind its electronic counterpart primarily due to the fact that digital optical device development is in its infancy. They predict near-term systems will be electrooptic, with each technology providing its strength to the problem at hand. >

Optoelectronic interconnections for integrated circuits

Abstract: The optoelectronic interconnection of the present invention provides a means for interconnecting a plurality of integrated circuits and each having at least one termination. The termination includes a transmitting section and a receiving section. Each transmitting section includes means for converting an output electrical signal from the integrated circuit to an optical signal in the form of a beam and an output grating for emitting the optical beam from the integrated circuit. Each receiving section includes an input grating for receiving an input optical signal in the form of a beam, means for amplifying the optical signal and a photodetector for converting the optical signal to an electrical signal which is fed to the circuit. The integrated circuits may be mounted adjacent each other with the output signals being emitting from the integrated circuits in the same direction. A reflector is mounted over the integrated circuits to reflect an output signal beam from the transmitting section of one integrated circuit to the receiving section of another integrated circuit. Each of the transmitting sections is capable of varying the angle at which the output signal beam is emitted therefrom so as to varying the integrated circuit to which the beam is reflected.

Experimental measurements and theory of first passage time in pulse-modulated semiconductor lasers

Abstract: The statistical properties of the first passage time T, the time delay between the electrical switch on instant and the attainment of a fixed value of the output optical power in pulse-modulated semiconductor lasers, are measured by three different techniques The measurements show that for lasers initially biased under threshold, the amount of time jitter defined as the standard deviation of T, is systematically larger in single-mode than in multimode lasers and is essentially determined by the value of the output optical power corresponding to the on state An analytical theory which gives the reason for the phenomenon is also developed Computer simulations of the process in agreement with the experimental and theoretical results are presented >