Showing papers on "Optical switch published in 1975"

Electrically switched optical directional coupler: Cobra

Abstract: We report the realization, in titanium‐diffused lithium niobate, of an integrated optical switch/modulator consisting of an active directional coupler with a novel electrode configuration. Efficient switching is observed with 6 V applied.

A new waveguide switch/modulator for integrated optics

Abstract: A waveguide optical switch and/or modulator device is described that uses a single‐mode waveguide version of the Mach‐Zehnder interferometer. A mode selective branching waveguide is used for switching, and modulation can be accomplished without external polarizers in single‐mode waveguides. The operation of a 1×2 switch fabricated by diffusion techniques in ZnSe is described.

Microwave switching by picosecond photoconductivity

Abstract: Bulk photoconductivity produced by the absorption of picosecond optical pulses in silicon transmission-line structures has been used to switch and gate microwave signals. The technique permits the generation of microwave and millimeter-wave pulses as short as a single cycle, and requires only a few microjoules of optical energy. The basic features of the device are illustrated with switching experiments at 1 GHz and 10 GHz, and the results are discussed with reference to the physical properties of the high-density plasma responsible for the switching.

Keyboard using optical switching

Abstract: The invention relates to keyboard devices using optical switching and includes novel light distribution means to multiple fiber optics, switching means between fiber optics, and collection means from multiple fiber optics to a single point.

Switch assembly having electrically illuminated character display devices between transparent actuators and switch arrays

Abstract: A switch assembly having a lighted display module for programmable character display where the module is an active part during switch actuation since the module is displaced by and transmits an applied switch actuating force. The switch assembly consists of electromechanical switch arrays having the illuminated solid-state programming character display (LED-type) disposed above the switch array. Transparent pushbuttons are illuminated when depressed. The electromechanical switch arrays consist of a matrix of conventional dome switches although other conventional types of switches may be used.

Optical crossbar switching network

Abstract: An optical switching network employing a plurality of optical switching crosspoints is implemented by providing the first and second pluralities of strip waveguide channels passing one over the other in parallel planes separated by an intervening medium. The implementation is further characterized by including at each of the proposed switching crosspoints, that is, at the regions of closest approach of the different strip guides, beam-guide couplers such as grating-type couplers to couple the modulated optical energy from one of the first plurality of channels to one of the second plurality of channels through an intervening, supporting medium. There are provided two couplers at each optical crosspoint; and they are controllable between coupling and noncoupling conditions with respect to their respective waveguide channels.

Optical cross-point switch

Abstract: An optical cross-point switch is disclosed which has the capability of connecting any of a multiplicity of input signals to any of a multiplicity of output lines, in any order in a non-interfering and non-blocking manner. The cross-point switch includes n input circuits (where n is an integer greater than one) and an output circuit associated with each input circuit. An n array of light emitting diodes is connected to each input circuit for transforming input electrical signals applied to the input circuits into optical radiation. A photosensor is connected to each output circuit for transforming incident optical radiation into output electrical signals. A lens, or fiber optic, system is disposed between the light emitting diodes and the photosensors for focusing optical radiations eminating from each array of diodes onto a separate photosensor. An input and output address decoding and selection circuit is coupled to each array of light emitting diodes to selectively enable one diode of each array so that each input circuit may be electro-optically coupled to a selected output circuit.

Adjustable optical switch or modulator

Abstract: An optical switch of the switched directional coupler type is provided with an adjustable cross-over state as well as an adjustable straight-through state, in order to provide reduced crosstalk in the cross-over state, for example, when the switches are used in an optical switching system. The improved switch is based on asynchronous or phase-mismatched coupling between two parallel optical strip guides driven by electrodes to which the voltage is applied. In order to use phase-mismatched coupling instead of phase-matched coupling for the cross-over state, in order thereby to obtain electrical adjustability of that state, the driving electrodes are split into two or more sequential sections, thereby defining two sequential coupling sections of the parallel optical strip guides. The cross-over coupling is then achieved by switching the mismatch conditions so that at the point of partial coupling the "nonoriginating" guide appears to the coupled optical waves to be the "originating" guide.

Electrically switched optical directional coupler: COBRA

Abstract: We report the realization, in titanium‐diffused lithium niobate, of an integrated optical switch/modulator consisting of an active directional coupler with a novel electrode configuration. Efficient switching is observed with 6 V applied.

A planar electrooptic-prism switch

Abstract: A novel electrode configuration for producing a prism-like deflector when applied to a planar optical waveguide is described. A prism deflector on a Ti-diffused LiNbO 3 waveguide was operated as a bipolar switch for electrode voltages of ± 15 V.

Broad bandwidth optical modulator and switch

Abstract: A modulator and switch for optical energy includes an optical waveguide dning a path for the propagation of optical energy, a source of microwave energy, and at least one strip transmission line disposed in co-directional proximity relative to the optical waveguide and connected to the source of microwave energy. The strip transmission line is designed to have dimensions and dielectric constants for producing a propagation velocity of the microwave energy substantially equal to the propagation velocity of the optical energy in the optical waveguide. A suitable microwave load is connected to the transmission line for completing an electrical circuit with the source of microwave energy.

Generation of a short optical pulse of arbitrary shape and phase variation

Abstract: It is shown that the problem of generating an optical pulse of arbitrary shape and phase may be reduced to the problem of producing an arbitrary spectral filter. This generalizes the short-pulse generation techniques, which are based on the laser breakdown switch, as the active element. We examine the extent to which any desired filter may be realized in practice, and some examples are given.

Light switch with delayed turnoff

Abstract: An improved switch for controlling electrical circuits comprising a conventional mechanical on/off switch employing a solid state electronic network connected in parallel therewith for providing a current path for a limited period of time following the opening of the mechanical switch thereby producing a delay in the de-energization of the circuit.

Electro-optical switch and a method of manufacturing same

Abstract: The electro-optical switch according to the invention is formed by parts of two guides made of a ferro-electric material previously polarized in a suitable fashion, enclosed between two electrodes; the application of a voltage between the two electrodes has the effect of varying the refractive index of each of the guides in relation to the other and, consequently, of making it possible to enable or inhibit energy coupling between the two guides. Such a device is applicable in particular to integrated optical circuits.

Motor protector circuit

Abstract: A circuit useful to protect motors and other dynamoelectric machines from overtemperature conditions caused by a fault condition such as locked rotor, overcurrent, or the like. The circuit comprises first and second tuned branch circuits coupled to the power lines of the motor or other machine along with an oscillator circuit and detector circuit and a switch to change the effective impedance of one of the tuned circuits. The tuned circuits each includes a series connected inductance and capacitance while the switch, which can be an electro-mechanical device such as a heat responsive thermostatic switch, or a solid state switch such as an NTC or PTC thermistor is connected around one of the components of one of the tuned circuits. The oscillator may be a conventional one adapted to provide a selected frequency, preferably high relative to that of the motor power supply. The detector, which also may be of a conventional type and the oscillator are both coupled to one of the power lines of the motor by respective toroid cores through which the power line passes intermediate the tuned circuits. When the switch is in one state the tuned circuits will resonate enabling the detector to detect the signal and to give an output thereby effecting indication of a fault condition or deenergization of the motor. When the switch is in its opposite state the tuned circuits will not resonate, and there will be no output signal given by the detector.

Crosstalk reduction in optical switching.

Abstract: All optical switches, in practice, send some fraction of their input light to the wrong output ports. This optical crosstalk occurs because the structural and operational parameters of the optical switch cannot be controlled with sufficient accuracy or because of sensitivity to changes in ambient conditions. The attempt to achieve low crosstalk may impose constraints on the switch's construction or environment that cannot readily be met. Therefore, an alternate way of reducing crosstalk is needed. This Letter presents a technique for improving the crosstalk properties of any type of optical switch. The technique proposed here is to build a composite optical switch from two or more individual switches and to absorb leakage light by terminating the unused ports of the composite. The composite is functionally equivalent to a single switch but reduces the crosstalk geometrically in proportion to the number of single-switch structures used. Although the increased number of elementary switches increases the system complexity, it does represent a means for achieving higher switching performance. It also may reduce over-all cost by relaxing manufacturing tolerances. The compounding of optical switches is analogous to a method found in the electrical art where an improved on/off ratio in rf switching has been attained with a series-shunt or series-shunt-series arrangement of transistors. An important application of low crosstalk optical switches is in an optical matrix whose function is to make an alterable interconnection of m optical fibers with a second group of m fibers. A one-to-one mapping of inputs onto outputs is generally desired. For this function, an m × m array of composite low-crosstalk four-port optical reversing switches can be used in a crossbar geometry where m out of m crosspoints are actuated (one per row and one per column). For the composite crosspoint switches, one can use a pair of elementary four-port reversing switches. The two states of each elementary optical switch are shown symbolically in Fig. 1. The optical leakage or crosstalk is denoted by εa in state A (the off-state) and εb in state B (the on-state). In the X and Y input channels, the optical signal strength is assumed to be unity, though the leakages εa and εb are, by definition, much less than unity. At each output port of the switch, the signal-to-crosstalk ratio (S/C ratio) is (1 – εα)/εα in the off-state and (1 – εb)/εb in the on-state. Figure 2 illustrates symbolically how a low-crosstalk switch is created by joining two elementary devices with their off-state leakages in cascade. Figure 2 shows the onand off-states of the composite in the circuit representa-

Isolation Amplifier with Combined Magnetic and Optical Coupling

Abstract: The amplifier presented in this paper is suitable for isolated acquisition of analog signals in the frequency range from dc to more than 10 MHz. It employs a combination of magnetic and optical isolation techniques which gives to the circuit good features of speed and precision.

Reversible recording of optical information in metal-dielectric-semiconductor structures

Abstract: An investigation was made of the charging of traps in the dielectric layers of a metal-siliconnitride/ silicon-dioxide-semiconductor structure subjected to electrical pulses. An analysis was made of the methods for optical switching of this structure by laser radiation and for photoelectric reading. The principal energy and time characteristics were determined for an optical memory based on this structure. Organization of an optical reversible memory of 108 bit capacity was considered.

Low energy switching circuit

Abstract: Switch for use in low energy circuit and which is arranged to switch a larger voltage than required by driven circuits to insure breakdown of insulating film on switch contacts.

Optical Switch Study.

Abstract: : Nineteen techniques for implementing an optical communications switch in an integrated optical circuit have been examined. The optical matrix switch is intended to interconnect n optical inputs with n optical outputs at a 10 GHz bandwidth. The most promising optical switching approaches were found to be electrically-controlled, optical directional-couplers and electro-optic, Bragg, diffraction-gratings. Both are realizable in optical microcircuit form. An optical balanced bridge is the optimum form of the coupler switch. The switchable couplers can be built from optical channel waveguides that have 2D mode confinement, while the gratings would be embodied in a slab guide with 1D confinement. The latter arrangement is more vulnerable to optical crosstalk in a matrix. Electro-optic phase perturbation in the deflectors and couplers is preferred for its simplicity, low driving power, and nanosecond switching speeds. An n squared matrix array of switches has been designed with 2n absorbing terminations at the unused ports.

Optical waveguides and devices

Abstract: A variety of practical or potential uses of low‐optical‐loss waveguides and devices for light modulation, deflection, and switching are reviewed. Emphasis is given to those that most likely will become necessary replacements of the bulk for systems involving signal processing, imaging radar, and optical communications. Both the optical properties and structural characteristics of these waveguides suitable for active and passive device applications will be detailed.

Integrated Optical Switches.

Abstract: : Integrated optical switches for multimode fiber-optic communication systems have been investigated theoretically and experimentally. Thick film (20 to 100 lambda) optical waveguide structures are judged optimum for the switching devices. The first part of this report shows how the authors arrived at the thick-film technology approach. The principle of optical brightness conservation imposes theoretical limits on the maximum energy transfer between various fiber and film geometries. The consequences of the coupling limits on fiber-optic systems are spelled out in Sec. 2. Two types of fiber-optic switches, refractive and diffractive, are described in Sec. 3. Experimental results are presented for acoustooptic Bragg devices, and electro-optic multi-prism devices. Section 4 presents a detailed computer analysis of a phase modulation switch, which consists of a relative phase shifter for TE and TM modes (an electro-optic polarization rotator) and a passive beam-discriminator.

An optical switch

Abstract: Thesis 1975 BS--Massachusetts Institute of Technology Dept of Electrical Engineering and Computer Science