Showing papers on "Optical switch published in 1982"

The nonlinear coherent coupler

Abstract: This paper discusses the nonlinear coherent coupler (NLCC), a device useful for optical processing, but not bistable. This device utilizes the coherent interaction of two optical waveguides placed in close proximity. Because of the evanescent field overlap, these waveguides periodically exchange power. Nonlinear interactions modify the exchange of power and lead to strongly nonlinear transmission characteristics.

Optical switching in semiconductor organic thin films

Abstract: Semiconducting organometallic films such as copper tetracyanoquinodimethane (CuTCNQ) have been observed to switch between two stable states when exposed to optical radiation. Observations of switching between two states in these films have been made by Raman spectroscopic methods and direct observation of electrical resistance changes. Line or pattern generation is observed for exposure above certain threshold levels. These effects are observed in a wide range of Cu and Ag organometallic compounds.

On the physical limits of digital optical switching and logic elements

Abstract: In this paper we identify and discuss some fundamental physical mechanisms that will provide limits on the speed, power dissipation, and size of optical switching elements. Illustrative examples are drawn primarily from the field of bistable optical devices. We compare the limits for optical switching elements with those for other switching technologies, and present a discussion of some potential applications of optical switching devices. Although thermal effects will preclude their wide application in general-purpose computers, the potential speed and bandwidth capability of optical devices, and their capability for parallel processing of information, should lead to a number of significant applications for specific operations in communication and computing fields.

Electro optic switch

Abstract: An optical switch utilizes a birefringent device to cause orthogonally polarized components of an arbitrarily polarized incident light beam to propagate along separate paths. A polarization rotator is positioned in one path to rotate the polarization of the light beam propagating therealong to that of the light beam in the other path. The two paths are simultaneously deflected to selected parallel paths in accordance with the switching desired. A second polarization rotator reestablishes the initial polarization and the beams are recombined by a second birefringent device to emerge from the selected output terminal as an arbitrarily polarized light.

Electrowetting optical switch

Abstract: Continuous electrowetting (CEW) and refractive index matching have been used as the physical basis of an optical switch for multimode fibers This switch has low cross talk (∼−30 dB), fast response times (∼20 ms), low operating voltage (∼1 V), and low power consumption (∼1 μW)

High-current InGaAsP-InP phototransistors and some monolithic optical devices

Abstract: High-gain InGaAsP/InP heterojunction phototransistors (HPT's) have been fabricated by a liquid-phase epitaxial (LPE) technique. A collector current as high as 170 mA has been achieved at a 2-V bias and a 155-µW incident-light power. The optical gain is 1180. A monolithic optical device has been constructed in a InGaAsP/InP system which includes the HPT and a double heterojunction (DH) light-emitting diode (LED). The monolithic optical device is designable as an optical switching and an optical bistable or a light amplification device by controlling positive feedback between the HPT and the LED. A light amplification system comprised of a discrete InGaAsP/InP laser diode and a high-current HPT, has exhibited incoherent-coherent conversion with a positive amplification.

Integrated optical switch matrix for single-mode fiber networks

Abstract: Design analysis and experiments on optical directional coupler switch integration into an LiNbO 3 chip with arrayed fiber pigtails has been made at 1.3 μm wavelength. A limitation for high integration was discussed by taking into account radiation losses at connecting waveguides between switch elements and at the input/output curved waveguide, switching voltage, and crosstalk caused by applied electric field leakage. An optimum designed low-loss 4 × 4 switch matrix with arrayed fiber pigtails at 1.3 μm wavelength has been developed. Its insertion loss was measured to be as low as 6 dB.

Capacitor discharge circuit

Abstract: A capacitor discharge circuit constructed by a combination of a mechanical switch and an electronic switch. The electronic switch is automatically turned on with a predetermined time delay after closing of the mechanical switch. The mechanical switch is used to completely separate a high voltage-large capacity capacitor from a load when the discharge operation is not required. The wear and tear of contacts in the mechanical switch can be avoided by the delayed operation of the electronic switch.

Polarization-insensitive optical switch and multiplexing apparatus

Abstract: Polarization-insensitive optical switch and dual channel carrier multiplexer includes a polarization beam splitter for receiving an input collimated beam which has arbitrarily polarized components, splitting the beam into the two components. One of the components is rotated by a 1/2 wave plate so as to yield a polarized beam which is polarized in the same direction as the other beam. The two polarized beams are then applied to a polarization sensitive interferometric multimode fiber optic switch and modulator. The output of the interferometric multimode fiber optic switch and modulator contains two beams, both polarized in the same direction. One of the beams is rotated ninety degrees by a 1/2 wave plate, and the two mutually perpendicularly polarized beams are then recombined by a polarization beam splitter operated in reverse to yield an output beam containing mutually perpendicular components.

2 × 2 optical waveguide matrix switch using nematic liquid crystal

Abstract: A 2 × 2 nonblocking optical matrix switch, composed of four elemental switches formed in a slab waveguide, is described. Switching action is based on total internal reflection caused by an electrically controlled change in refractive index of the liquid crystal. Propagation loss was remarkably reduced to 2.3 dB/cm, both by using liquid crystal as a cladding layer and by operating at the 1.31 μm wavelength. The experimental matrix switch exhibited 7.3-7.7 dB insertion loss, -17.3 to -18.2 dB crosstalk, and a 14° switching angle.

Electrooptic 4 × 4 matrix switch for multimode fiber-optic systems

Abstract: A new fiber-optic switch for multimode fiber networks has been developed. This voltage-controlled device can switch light from any of four input fibers to any of four output fibers. Four input/output connections are made simultaneously, and the matrix has twenty-four such states. No moving parts are needed because the switching is accomplished with an electrooptic effect in nematic liquid crystals. Low levels of optical crosstalk, ∼40 dB below the output signal level, are obtained with a unique two-stage architecture. The design, construction, and observed performance of this optical switch are described.

Polarization-independent optical switch with multiple sections of Δβ reversal and a Gaussian taper function

Abstract: Multiple section \Delta\beta reversal polarization-independent integrated optic switches have been designed and demonstrated at a 0.83 μm wavelength. These switches use a Gaussian taper function to achieve low crosstalk in the parallel state. Calculated switch characteristics as related to an ideal Gaussian taper and approximations that can be fabricated by mask making are described. Experimental demonstration shows that these switches have useful switching characteristics with relatively high switching voltages.

Line switch having distributed processing

Abstract: A line switch for a digital telephone switching system utilizes distributed processing. The line switch comprises one or more switch modules. Each switch module is coupled to a central office switching system via one or more PCM lines which utilize common channel signaling. Each switch module comprises groups of line circuits, each line circuit being coupled to a subscriber line. Three separate distributed processor functions are provided in each line switch module. A first processor is utilized to communicate with the central office switching system and to coordinate the operations within the line switch module. A second processor is provided to control clock generation and rate conversion circuits. Each group of line circuits includes a third processor to control the operations of the line circuits and to gather information from the line circuit. A busing arrangement is provided within the line switch such that both control information and PCM voice data are routed throughout the line switch.

Electrowetting switch for multimode optical fibers

Abstract: Lightwave communications networks may require highly reliable optical switches for multimode fibers. Such switches should have low loss, low cross talk, low power consumption, and low operating voltages. Three types of switch have been proposed: mechanical: electrooptic; and liquid crystal. Mechanical switches, which operate by moving either the fibers or other optical components, are the most widely used. Alternatives to mechanical switches have been sought because these switches require high driving power (>20 mW) and are subject to wear. Electrooptic switches eliminate these problems and are significantly faster. However, both insertion losses and cross talk are higher than for mechanical switches, and their use with multimode fibers requires large voltages. Liquid crystal switches are low voltage devices, but their cross-talk performance is relatively poor, and the long term stability of liquid crystals in field conditions is not established.

Fiber optic loop system with bypass mode

Abstract: An optical data is transmitted from station to station through an optical T-coupler attached to each station. The optical T-coupler splits the data signals into two paths with identical data being transmitted to the attached station and also the succeeding station. An optical to electronic conversion takes place as the data enters the station. Electronic digital switching within each station selects a "normal" mode of receiving data from the preceding station when data is valid or a "bypass" mode of receiving data from the station which precedes the preceding station. Switching from normal to bypass mode is performed by electronic switching and requires no optical switches.

Semiconductor analog switch circuit with compensation means to minimize offset of output voltage

Abstract: A semiconductor analog switch circuit device is disclosed in which a second analog switch circuit is connected in parallel with a first analog switch circuit. The first and second switch circuits are controlled by control pulses with opposite phases. An input signal is applied to one of the parallel junctions of the first and second analog switch circuits, while an output signal is derived from the other parallel junction.

Nonmechanical optical switch for single-mode fibers.

Abstract: This paper introduces a bistable nonmechanical optical switch for single-mode optical fibers. A 1-input/2-output device for the 1-μm wavelength range, the optical losses of the switch are independent of the polarization state in the input fiber. The insertion losses for the optical signal from the input fiber to the output fiber are 1.4 dB and the crosstalks are −28 dB at 1.3-μm wavelength. Switching is performed by a 20-μsec one-shot pulse with a maximum current of 500 mA. The voltage to switch the optical path is 5 V.

Switched-mode power supply

Abstract: A switched-mode power supply providing high speed switch operation and high efficiency is disclosed. Faster switch turn-off is accomplished by means of an additional primary winding in the power supply's converter transformer which causes switching current to be diverted from the switch element when the oscillating switch transitions to the cut-off state. More rapid switch turn-on is achieved by shunting current from the regulation circuit of the power supply during initial switch turn-on in providing the entire switch control output of a blocking oscillator to the switch element. Power supply regulation is provided by an optical link including a photodiode coupled to a secondary of the converter transformer and a phototransistor which controls the input provided to the switch by the blocking oscillator. More rapid switch operation improves the inductive transfer of energy in the switched-mode power supply thus increasing power supply efficiency and prolongs the operating lifetime of the power supply's switch element.

Optical switch array

Abstract: An optical switch array including a substrate in the main surface of which is formed a plurality of inlet waveguides arranged side-by-side with a predetermined pitch and a like plurality of outlet waveguides each arranged in line with the corresponding inlet waveguide with a gap therebetween is provided. The gap is filled with a material having a temperature dependent index of refraction, which is lower in value than the waveguides at normal temperature but becomes comparable in value to the waveguide when heated thereby optically coupling the paired inlet and outlet waveguides.

Bistable magnetooptic switch for multimode optical fiber

Abstract: A bistable nonmechanical optical switch for multimode optical fiber is presented. It is a 2-input/2-output device for the 1-microm wavelength range. The optical characteristics are independent of the polarization state of incident light. The switch consists of Faraday rotators of thin plates of yttrium-iron-garnet single crystal, electromagnets whose cores are made of semihard magnetic material, halfwave plates of crystal quartz, polarizing prisms of rutile, and lenses. Switching is performed by one-shot 3-V 20-microsec pulses with a maximum current of 500 mA. The 1.5-dB insertion losses and -32-dB cross talk were obtained at a wavelength of 1.3 microm.

Interaction of a bistable injection laser with an external optical cavity

Abstract: Experimental results on interactions of a bistable laser with an external optical cavity are presented. Switching of a bistable injection laser can be done by varying the amount of optical feedback. The optical switching is accompanied by a switching of the voltage across the absorber section. This can be utilized in digital optical disk readout. A bistable laser with an antireflection coating on one facet is more suitable for this task. No pulsations can be observed in a bistable laser with optical feedback if the absorber section is biased with a constant current source; but when it is biased with a voltage source, pulsation occurs at the external cavity round trip frequency. This indicates that even though the intrinsic absorption of the semiconductor material does not saturate easier than the gain, the presence of such absorptions in GaAs lasers can still produce pulsations when the electrical aspect is taken into account.

Waveguide type optical switch

Abstract: PURPOSE:To obtain a switch with excellent characteristic and can be worked easily, by providing a waveguide whose end part has been tapered, on the first waveguide, providing a liquid crystal layer on said tapered part, controlling a refractive index of the liquid crystal layer by an electric field or a magnetic field, and switching a propagation light beam to the second waveguide CONSTITUTION:A waveguideIconsisting of a waveguide layer (1561 refractive index) glass spattered film 7 and an intermediate layer (a glass spattered film of 1464 refractive index) 8 is formed on a Vycor glass (1457 refractive index) substrate 6 Subsequently, a tapered waveguide layer 9 is formed by an SiO2- Ta2O5 glass spattered film (1748 refractive index), and on its tapered part, a liquid crystal layer 10, for instance, a pneumatic liquid crystal (its refractive index) can be controlled extending over 148-160 by an electric field or a magnetic field) layer 10 is provided, and on the flat part of the layer 9, a clad layer 11 is provided by use of a glass spattered film On the liquid crystal layer 10, liquid crystal sealed glass 12 is fixed by use of an adhesive agent 13 An optical switch operated stably is obtained by applying voltage from lead parts 16a, 16b placing an optical propagation part between them, to parallel band- like electrodes 15a, 15b provided on the tapered part of the layer 9, and changing the refractive index of the liquid layer 10

Optical switching method

Abstract: PURPOSE:To obtain a stationary switching state free of variation in the quantity of light by preventing a drift phenomenon by applying three electrodes, provided on a substrate having optical waveguides, with out-of-phase AC or rectangular voltages. CONSTITUTION:On LiNbO3, Ti is dispersed to form optical waveguides 1 and 2 which adjoin to each other at an about 3-7mum interval; and electrode 3 is provided between the optical waveguides 1 and 2, and electrode 4 and 5 are provided outside of them. The optical waveguides 1 and 2, while no voltage is applied, have the same propagation constant and are constituted to complete coupling length, so light 8 incident to the optical waveguide 1 is coupled with the optical waveguide 2 to be emitted as light 9. When the electrode 3 is grounded and the electrodes 4 and 5 are applied with 180 deg. out-of-phase rectangular voltages, no DC electric-field drift phenomenon is caused and a difference in refractive index (i.e. propagation constant difference) between the optical waveguides 1 and 2 becomes constant, so that the quantity of emitted light 10 is nearly constant.

Optical digital high-speed transmission: General considerations and experimental results

Abstract: Laboratory experiments on digital optical transmission systems at bit rates of 1 and 2 Gbits/s are described. Systems with graded-index and single-mode fibers in the optical short and long wavelength region were investigated. All systems include complete circuits for clock and signal regeneration. Special emphasis was laid on the development of electronic circuits for gigabit signal processing and on the investigations of the noise sources of the optical channel, which appear especially pronounced in broad-band systems. The experimental results confirm the possibility to set up reliable high-speed optical transmission systems under laboratory conditions with available components. The remaining problems are of optical and not of electronic nature, despite the fact that monolithic integrated circuits for gigabit applications are hardly commercially available today.

Liquid-phase epitaxial growth of bismuth silicon oxide single-crystal film: a new optically activated optical switch

Abstract: A single-crystalline double-layered structure of a pure (80-μm)/doped (39-μm)/pure Bi12SiO20 (BSO) substrate was grown for the first time by a new liquid-phase epitaxial griowth to form an optical waveguide. The waveguide layer is BSO doped with CaCO3 (0.1 wt. %) and Ga2O3 (0.197 wt. %) and has a refractive index 0.07 % higher than the substrate. The optical absorption coefficients were decreased by more than 1 order of magnitude by doping with the elements Ca and Ga. The high-sensitive photoconductivity of pure BSO was also reduced. Using these unique properties, we have constructed a new type of optically controlled planar optical switch.

Optical switch device

Abstract: By an electro-optical switch or an optical switch element utilizing diffraction by a surface acoustic wave, an input light beam is first switched over to one of light beams two or a multiple of two in number and propagating in different directions. By a surface acoustic wave which is discretely variable in frequency, the light beam in each of the different propagation direction is deflected at angles in accordance with the varying frequencies while propagating through an optical waveguide layer. It is possible to obtain by switching a very large total number of output light beams which are equal in number to the number of resolvable deflected light beams obtained in the frequency bandwidth of one surface acoustic wave, multiplied by the number of light beams obtained by switching with the optical switch element.

Optical scanning system including a rotatable drum with mirrors and including a rotatable optical shutter

Abstract: An optical scanning system includes scanning means arranged to scan an object field and comprising, in one form, a rotatable drum (10) carrying a plurality of pairs of mirrors (12, 13). A detector (21) is provided which is sensitive to optical radiation directed on to it by the scanning means. Means, such as telescopes (17, 22) collect radiation from at least two fields of view for presentation to the object field of the scanning means. Optical switching means are provided so that radiation reaches the detector (21) from each field of view in turn. The switching means may be an optical shutter (14) having reflective regions (15) and transparent regions (16).

Circuit for interfacing a processor to a line circuit

Abstract: A line switch for a digital telephone switching system which uses distributed processing, has one or more switch modules, 1a, 1b, each coupled to a central office switching system via one or more PCM lines PCMA, PCMB using common channel signalling. Each module comprises groups of line circuits 11, each coupled to a subscriber line. Three separate distributed processor functions are provided in each line switch module. A first processor communicates with the central office switching system and coordinates the operations within the line switch module. A second processor controls clock generation and rate conversion circuits. Each group of line circuits includes a third processor to control the operations of the line circuits and to gather information from the line circuit. A busing arrangement is provided within the line switch such that both control information and PCM voice data are routed throughout the line switch. Communication between the processors is via common buses carrying TDM-PCM data and control data. A standardised interface circuit is provided which interfaces each line circuit to the third processor and also to the busing arrangement.