Abstract: A new pipeline method and apparatus for photonic analog-to-digital converters (ADCs) utilizing wavelength division multiplexing (WDM) and distributed phase modulation is disclosed. The analog-to-digital conversion is performed within the optical system of the ADC, and thus the optical output is a digital bit pattern. The optical output of this system thus facilitates ADC conversion at much higher speeds than available with conventional electronic ADCs. Phase modulators and polarization-based optics are used to map an input analog waveform into a binary output.

Abstract: A new pipeline method and apparatus for photonic analog-to-digital converters (ADCs) utilizing wavelength division multiplexing (WDM) and distributed phase modulation is disclosed. The analog-to-digital conversion is performed within the optical system of the ADC, and thus the optical output is a digital bit pattern. The optical output of this system thus facilitates ADC conversion at much higher speeds than available with conventional electronic ADCs. Phase modulators and polarization-based optics are used to map an input analog waveform into a binary output.

Abstract: This invention includes a current output sensor, and a current AD conversion means which is connected to the output side of the current output sensor and has a current mirror circuit arranged on the input side of a comparator in order to directly A/D-convert an output from the current output sensor. A signal can be stably processed with a small circuit scale and low current consumption.

Abstract: A circuit for selectably generating a plurality of preselected digital output signals which are precise and accurate, and among which the circuit can switch rapidly. In one embodiment, the outputs are connected to analog circuit signals, and drive a optical laser such that choice of the particular outputs of the circuit permits controllable switching of the laser output wavelength.

Abstract: An A/D converting device comprises; a plurality of A/D converters connected in parallel with each other, for carrying out a converting operation a plurality of numbers of times, in which an analog signal is converted into a digital data, a selecting circuit for selecting each A/D converter from the plurality of A/D converters at each sampling timing during the converting operation to sample the converted digital data, a selecting circuit controlling unit for controlling the selecting circuit so that when one A/D converter is selected at one sampling timing during the Nth converting operation, another A/D converter is selected at the one sampling timing during the (N+1)th converting operation, an adding circuit for integrating the digital data sampled at the one sampling timing during each converting operation, and a processing unit for processing the integrated digital data.

Abstract: An electron beam analog to digital converter wherein an input signal to be quantized is applied to the deflection circuitry of an electron beam generation device where the electron beam is made to sweep an angle proportional to the amplitude of the input signal in a first orthogonal direction (horizontal) across a linear array of detector elements which generates an output signal at the angle of deflection. A sinusoidal reference signal is simultaneously applied to a second set of deflection plates which causes electron beam to sweep in a second orthogonal direction (vertical) whereupon the deflected electron beam periodically sweeps across the detector array and a time sample of the output voltage is generated during a crossover interval. The detection voltage is then converted to an output signal having a binary value corresponding to the amplitude of the analog input signal.

Abstract: Luminance or color modulation of a display screen is used to transfer data to an external receiving device. At least a portion of the display screen is modulated, such as by intensity modulation, to represent a data digit. By using a plurality of intensity levels greater than 2, it is possible to represent data digits having a numerical base greater than 2. For example, providing modulation with ten different intensity levels allows each modulation “dwell” to represent a decimal digit. The modulation is sensed by a photodetector in the external receiving device and converted to the corresponding data digit.

Abstract: Apparatus and method for high-speed analog-to-digital conversion employs photonic circuits with variable light-absorption. A coherent light source is clocked to produce a stream of coherent light pulses onto which is modulated an analog signal to be converted to digital form. An optical splitter divides the stream of pulses into a number of streams that is proportional to the resolution sought. A passive photonic quantizer absorbs, to a predetermined degree, the light energy of the incident pulse streams. The output of a fully absorbed pulse does not trigger a comparator. Pulse streams of sufficient intensity pass through the light absorbers, and their output does trigger the comparator. The output state of the comparators may be read into a digital memory to form a digital word that represents the analog signal during any discrete clock interval. Most of the elements of the apparatus can be fabricated on a substrate of photonic semiconducting material.

Abstract: An HFC return path system uses digital conversion and transport at the fiber optic node, so as to replace analog laser technology with a high-speed baseband digital technology, thereby providing immunity from the troublesome analog laser impairments, enabling longer distances to be covered, potentially avoiding the need for hub repeater hardware required in analog systems, among other benefits.

Abstract: Encoders and decoders for applying composite codes to optical data signals include encoders and decoders for applying both subcodes and supercodes. The subcodes have a duration selected as less than or equal to an interchip duration or a chip duration of the supercodes. The encoders and decoders (“coders”) include fiber Bragg gratings configured to encode or decode a subcode, a supercode, or a composite code. By coding with a subcode coder and a supercode coder, a coder is reconfigurable by selecting different subcodes or supercodes. Communication systems and methods using composite codes are also described.

Abstract: An electrooptical scanning analog-to-digital converter for converting an analog voltage signal from a source to its corresponding digital equivalent in accordance with the invention includes a laser providing a beam having an initial position and multiple deflected positions. The voltage signal forms a deflection input to the laser. A first voltage of the voltage signal provides for the initial position of the beam and multiple other voltages of the voltage signal provide for the plurality of deflected positions of the beam. The invention also includes a phototarget array that has a first phototarget mapped to the first voltage of the voltage signal and multiple incremental phototargets each mapped to one of the multiple other voltages of the voltage signal. The first phototarget and the multiple incremental phototargets are arranged along an axis, which may be in one implementation substantially perpendicular to the initial position of the beam.

Abstract: An optical analog-to-digital converter (10) that makes use of a downward-folding successive approximation conversion scheme that employs subtraction of optical signals. A pulsed optical signal (20) to be converted is applied as an input to each of a plurality of converter channels (12, 14, 16, 18), where each channel (12, 14, 16, 18) outputs one of the bits of the digital output of the converter (10). The input signal (20) to each channel (12, 14, 16, 18) is sent to a thresholding device (24, 40, 60, 80) that determines whether the intensity of the signal is greater than or less than a predetermined threshold value. The first channel thresholding device (24) compares the input signal (20) to a threshold value that is one-half of a known maximum intensity. Subsequent channel thresholding devices (40, 60, 80) compare the input signal to a threshold value that is one-half of the intensity used in the previous channel in a downward-folding scheme.

Abstract: An optical-to-electrical converter includes an input port configured to receive an optical signal. The converter further includes a splitter configured to split the received I optical signal into a plurality of optical signals. An optical stage has a plurality of parallel stages, and each parallel stage receives a corresponding one of the plurality of identical signals and outputs a corresponding one of a plurality of sampled optical signals within a corresponding sampling window. A plurality of delay circuits receive a clock signal having a plurality of clock pulses separated by a clock period. The delay circuits respectively output a plurality of control pulses at a plurality of delayed timings with respect to each clock pulse of the clock signal. An electrical stage receives the plurality of sampled optical signals and processes the optical signals at a sampling rate corresponding to the clock period of the clock signal.

Abstract: A method and apparatus for data conversion using time manipulation is disclosed. Ultrafast analog-to-digital (A/D) conversion and digital-to-analog I/A) conversion are achieved by optoelectronic time-stretching or time-compression, respectively. A pulsed laser is chirped by frequency spreading the laser output in either discrete or continuous fashion. The chirped output is then modulated with the electrical signal, and then frequency spread again. The output of the modulated signal is detected with a photodetector to convert the optical signal to a time-manipulated copy of the electrical signal.

Abstract: Luminance or color modulation of a display screen is used to transfer data to an external receiving device. At least a portion of the display screen is modulated, such as by intensity modulation, to represent a data digit. By using a plurality of intensity levels greater than 2, it is possible to represent data digits having a numerical base greater than 2. For example, providing modulation with ten different intensity levels allows each modulation “dwell” to represent a decimal digit. The modulation is sensed by a photodetector in the external receiving device and converted to the corresponding data digit.

Abstract: An optical-to-electrical converter includes an input port configured to receive an optical signal. The converter further includes a splitter configured to split the received optical signal into a plurality of optical signals. An optical stage has a plurality of parallel stages, and each parallel stage receives a corresponding one of the plurality of identical signals and outputs a corresponding one of a plurality of sampled optical signals within a corresponding sampling window. A plurality of delay circuits receive a clock signal having a plurality of clock pulses separated by a clock period. The delay circuits respectively output a plurality of control pulses at a plurality of delayed timings with respect to each clock pulse of the clock signal. An electrical stage receives the plurality of sampled optical signals and processes the optical signals at a sampling rate corresponding to the clock period of the clock signal.

Abstract: An analog to digital converter has an optical pulse source generating an optical pulse chain having a plurality of optical pulses. An optoelectronic digitizer has a first input receiving the optical pulse chain. The digitizer has a second input for receiving the analog signal to be converted. The digitizer has a plurality of digital outputs. Each of the digital outputs corresponds to a range value. An electronic encoder receives the plurality of digital outputs. The encoder has an output in a predetermined digital format.

Abstract: An N-bit analog to digital converter for converting optical signals into digital form is disclosed. The converter comprises N optical signal channels, one channel for each significant bit of the N-bit digital representation of the optical signal. Each optical channel comprises optical waveguides and photodetectors for converting the optical signal into electronic signals. The sensitivity of the photodetectors in each channel varies from most significant to least significant bit in the digital conversion. The electronic signals drive high-speed switching devices, each of which is set to a different threshold depending on which bit of the digital conversion the switch delivers. There are N switching devices directly driven by the N photodetector channels yielding N digital bits representing the magnitude of the optical input signal.

Abstract: An apparatus for stabilizing optical interferometers utilized in an all analog to digital converter using an additional optical signal that differs in wavelength by a factor of two from the wavelength used for the analog to digital conversion is disclosed. The optical interferometers have an optical path length that is tunable. They develop a first interference pattern from the additional optical signal when the optical path length is a prescribed value. The interferometers develop a second interference pattern from the additional optical signal when the optical path length is not the prescribed value. Optoelectronic detectors are responsive to the optical interference pattern generated by the additional optical signal and develop electronic feedback signals when the first interference patterns are not present.

Abstract: An optical quantizer (10) that employs a chain of optical thresholding devices (16) positioned in the propagation path of an optical input beam (12) to be quantized. Each optical thresholding device (16) saturates and turns transparent if the intensity of the optical beam (12) that impinges it is above a predetermined threshold level designed into the device (16). If the input beam (12) saturates the optical thresholding device (16), the device (16) outputs an indicator signal (22) identifying the saturation. The input beam (12) propagates through the optical thresholding device (16) with some attenuation caused by the saturation, and impinges subsequent optical thresholding devices (16) in the chain. Eventually, the attenuation of the input beam (12) caused by the multiple saturations will decrease the beam intensity below the threshold level of the next optical thresholding device (16). The number of indicator signals (22) gives an indication of the intensity of the input beam (12).

Abstract: An optical analog-to-digital converter (10) which fully operates in the optical domain and utilizes an upward-folding successive approximation approach for conversion. The converter (10) includes a plurality of optical stages (14, 16, 18) where each stage (14, 16, 18) generates a digital bit. Each stage (14, 16, 18) includes an optical threshold switch (30, 56, 78) that sets the bit high when the switch (30, 56, 78) is closed. When a sample amplitude of the analog signal is compared to a threshold value and found to exceed the threshold value, the bit is set to "high" and the sample is passed directly onto the next stage (14, 16, 18). If the sample amplitude is found to be less than the threshold value, the bit is set to "low" and an intensity equal to the maximum signal intensity minus the threshold intensity is added to the sample amplitude. Each successive stage (14, 16, 18) compares the normalized signal sample to thresholds growing closer and closer to the maximum signal intensity.

Abstract: A fully optical converter for converting an analog signal into a digital signal includes an amplitude to optical wavelength converter for converting the analog signal into an optical signal which varies in wavelength in accordance with an amplitude of the analog signal, a splitter for applying the optical signal over a desired number of light paths, an interferometer connected to each of the light paths, unequal path lengths in each leg of the interferometers to allow optical interference to deliver a complementary sinusoidal transfer function to the optical signal to generate two complimentary output signals and a dual detector connected to each of the interferometers for generating a digital bit in response to the two complimentary output signals, wherein each of the digital bits together form a parallel digital word. The fully optically based converter is automatic and independent of interactive techniques, thus providing for an expedited conversion rate.

Abstract: An ultra-fast electrooptic analog-to-digital converter is described. The A/D converter includes an electrooptic modulator that generates a modulated light beam from an incident light beam in response to an applied modulation signal. An optical demultiplexer is positioned to receive the modulated light beam. The optical input of a respective one of a plurality of photodetectors is optically coupled to a respective one of a plurality of demultiplexed modulated light beams. Each of the plurality of photodetectors generates an electrical signal in response to an intensity of the demultiplexed modulated light beam that is coupled to its optical input. A plurality of charge comparators compares electrical signals generated in response to the intensities of the demultiplexed modulated light beam to a reference signal. The output of each of the plurality of charge comparators generates a digital representation of the incident light beam.

Abstract: A method for detecting data outputted from an optical coupler is presented comprising the steps of setting a reference recognizing level by inputting the data in an initial state to an A/D converter; recognizing the level of the data in a noninitial state as high if the level of the data at the non-initial state is greater than the reference recognizing level; recognizing level of the data in the non-initial state as low if the level of the data at the non-initial state is less than the reference recognizing level; and setting the level of the data at the non-initial state to equal the reference recognizing level if the level of the data at the non-initial state is recognized as low.

Abstract: An optoelectronic system is provided for converting analog electrical sigs into digital electrical signals. An optical carrier produced by a laser source is separated into spectral components. An electro-optical modulator modulates the optical carrier with a radio frequency input signal so as to produce an amplitude modulated optical output signal. The optical output signal is then outputted to a wavelength division demultiplexer which separates the output signal into a plurality of separate channels, based on wavelength. Photodetectors connected to each of the channels convert the separated signals into analog electrical signals. These analog electrical signals are outputted to a plurality of standard analog to digital converters which convert the analog electrical signals into digital signals.

Abstract: An electrostatic discharge protection device for protecting a mixed voltage integrated circuit against damage is provided which includes at least on pair of NMOS transistors connected in a cascode configuration. Each NMOS transistor pair includes a first transistor, having a drain region coupled to and I/O stage of the mixed voltage integrated circuit, and a gate region coupled to the mixed voltage integrated circuit's low power supply. The second NMOS transistor of the pair is merged into the same active area as the first transistor and has a gate region and a source region coupled to the ground plane of the mixed voltage integrated circuit. The source region of the first transistor and the drain region of the second transistor are constructed of a shared NMOS diffusion region.

Abstract: A frequency modulation-based optical analog-to-digital converter utilizes a downward-folding, successive approximation approach. A series of stages is utilized to generate bits in the digital signal. In each stage, complementary low and high bandpass filters collectively cover a bandpass frequency range from a low frequency to a high frequency. The high frequency filtered signal from the high bandpass filter is observed to obtain a bit in the digital word. By performing the folding operations in the frequency domain, the converter avoids the difficult task of optical power subtraction, relying instead on frequency down-conversions. The high frequency filtered signal passed by the high bandpass filter is then downconverted and added to the low pass filter signal to generate a modulated signal for the next stage.

Abstract: A high speed differential optoelectronic receiver comprises a first photodetector responsive to a first incident amplitude modulated optical signal and operative to develop a first electrical signal, a second photodetector responsive to a second incident amplitude modulated optical signal that is complementary to the first optical signal and operative to develop a second electrical signal, and an amplifier having a first input that is responsive to the first electrical signal and a second input that is responsive to the second electrical signal and is operative to provide a differential output signal that is proportional to the difference between the first and the second electrical signals. Also, a method for transforming complementary amplitude modulated optical signals into a complementary electrical output signal is invented.

Abstract: A monolithic light-to-digital signal converter (1.10) includes a photodiode array (1.24) having a plurality of sections with each section producing a current signal in response to incident light, a current-to-digital signal converter circuit (1.28) for converting selected ones of the current signals to a digital signal, and a control circuit (1.26) for scaling the digital signal in response to user supplied programming signals. The control circuit (1.26) also responds to user supplied programming signals to supply control signals to current-to-digital signal converter circuit (1.28). Current-to-digital signal converter circuit (1.28) is responsive to the control signals for combining selected ones of the current signals into a composite current signal and converting the composite current signal to a digital signal.

Abstract: A DAC is disclosed that includes a decoder having output lines corresponding to digits of digital data. The decoder generates an output corresponding to the value of the digital data on the output lines. The DAC further includes a constant current source, and output means connected to the constant current source for providing an output voltage by a flowing current. The DAC also has driver transistors, where each transistor is connected to one of the decoder output lines and to the constant current source. The output means conducts a current from the constant current source when the connected output line is activated. Current limit transistors are each connected to each one of the driver transistors. The decoder output lines are grouped so as to correspond to each of the ranges of a gamma compensation curve. A common reference voltage for each group is applied to a control terminal of the current limiting transistors associated with the output lines in each group.

Abstract: A personal digital assistant module with a local CPU, memory, and I/O interface has a host interface comprising a bus connected to the local CPU and a connector at a surface of the personal digital assistant for interfacing to a bus connector of a host general-purpose computer, providing direct bus communication between the personal digital assistant and the host general-purpose computer. In an embodiment, the personal digital assistant also has a means for storing a security code. The personal digital assistant according to the invention forms a host/satellite combination with a host computer having a docking bay, wherein upon docking a docking protocol controls access by the host to memory of the personal digital assistant based on one or more passwords provided by a user to the host. In another embodiment the personal digital assistant also has an expansion port connected to the local CPU, and expansion peripheral devices may be connected and operated through the expansion port.

Abstract: An N-bit analogue-to-digital converter can increase the resolution by 3 bits, by very precise coding of the differential phase at the output of the electro-optic phase modulator controlled by the electric signal to be converted. The optical signals obtained are processed by an electro-optic device that outputs electric signals that are functions of the sine and cosine of the phase. A coding device uses the symmetry of the trigonometric circle partitioned into four consecutive sectors between 0 and 27.pi. in order to convert the absolute values of the electric signals obtained on (N-3) bits, independently of the home sector of the phase. A transcoding device uses the value of the sine and cosine coded on (N-3) bits, to output a value V of the electric signal, on N bits, as a function of the home sector.

Abstract: Intrapulse Raman scattering is utilized in providing optical devices that can be adapted to perform various logic and switching functions. In a logic gate embodiment of the present invention, a plurality of pulses of the same central wavelength are coupled to produce an output pulse having a power level equal to the sum power level of the inputs. When the power level of a sufficiently narrow output pulse exceeds the Raman threshold, the output pulse experiences a wavelength shift of a magnitude that can be controlled by adjusting the input power. An optical filter selectively blocks coupler output pulses depending on the desired logical operation of the device. In a switch according to the invention, an input pulse and a control pulse are coupled, and Raman scattering of the output pulse is stimulated. The output pulse is applied to several output lines, each having a filter centered at a predetermined pass band.

Abstract: A distributed delta-sigma analog-to-digital (A/D) converter is partitioned between an ultrasonic probe and an imaging console which are coupled to each other by optical links. The ultrasonic probe houses an integrator for receiving an analog input signal and generating an integrated analog output signal. The integrated output signal is supplied to a light emitting diode for generating a light beam. The probe also houses photoconductive switches for coupling positive and negative reference voltages to a summing node of the integrator. The imaging console houses a photodiode for receiving the light beam via a fiber optic cable and converting the light beam to an analog electrical signal which is later converted to a digital signal. A feedback loop includes an internal A/D converter in the console that is coupled to the photoconductive switches via LED-generated light beams passed through other fiber optic cabling.

Abstract: An optical analog to digital converter for microwave signals in which the input to a Mach-Zehnder modulator/interferometer is split into two branches which are provided with respective laser carrier signals having a difference frequency equal to a desired conversion frequency. An input microwave signal is then used to modulate the carrier signal present in one of the input branches to the interferometer, and the resulting output signal is detected and compared with a predetermined threshold value to generate a binary 1 or 0 output. In a preferred embodiment, a plurality of such interferometers are arranged in a parallel configuration and the modulation of the respective carrier signals is scaled by a factor of two.

Abstract: The present invention provides an optical isolation amplifier which generates a low-noise analog output signal linearly related to an analog input signal and which conveniently fits within a conventional 8-pin dual in-line package. The optical isolation amplifier package includes an input chip having a sigma-delta analog-to-digital (A/D) converter for converting an analog input signal to a digital signal. The sigma-delta converter is used to modulate an off-chip LED which optically transmits the signal to a photodetector on a separate output chip having an accurate optical recovery section for reproducing the transmitted signal. Also contained on the output chip is a digital-to-analog (D/A) converter for converting the digital signal to an analog output signal linearly related to the analog input signal.

Abstract: An analog signal having a value A is converted into an n-bit digital signal. An optical calculation part performs a part of a calculation shown below for an A/D conversion as below.U.sub.i =[{{.SIGMA.(W.sub.ij .times.X.sub.j)+h.sub.i }.times.V}+A].times.Si . . . (1)The calculation of the equation (1) is performed fori=0, 1, . . . , n-1 respectively;the W.sub.ij is 0 if i.gtoreq.j.gtoreq.0, or -(2**j) if j>i.gtoreq.0; hi is -(2**i), or -{(2**i)-.epsilon.}(.vertline..epsilon..vertline..ltoreq.1);V and S.sub.i respectively have any desired positive values and the said .SIGMA. represents a summation of each expression following thereto for j=0, 1, . . . , n-1. The thresholding compares the result U.sub.i of the calculation of each equation (1) to a threshold value, and then 1 or 0 is selected. The result of the selection is then assigned to X.sub.i. The calculation of the equation (1) is then performed repeatedly until X.sub.i converge on solutions. The solution of each X.sub.

Abstract: Timing restoration for a series of input pulses is performed optically in a transmission or switching system, using a nonlinear material with negligible walk-off that also receives an essentially orthogonally polarized series of reference pulses. In the nonlinear material, the input pulses are frequency shifted by the presence of the reference pulses. For a material with negligible walk-off, the frequency shift only occurs when the pulses partially overlap, but not when the pulses are coincident. The frequency shifted output from the nonlinear material is supplied to a dispersive delay line that translates the frequency shift into a time shift, such that the input pulses are retimed by the reference pulses. If the nonlinear material has a nonlinear index of refraction n.sub.2 >0, then the dispersive delay line must have an anomalous Group Velocity Dispersion (GVD); on the other hand, if the nonlinear material has an index of refraction n.sub.2 <0, then the dispersive delay line must have a normal GVD.

Abstract: A general purpose programmable optical analyzer employs a nonlinear gain at the input stage of an analog to digital converter in order to limit the number of bits used to resolve shot noise.

Abstract: An analog to digital signal converter includes an integrator and a sample and hold circuit. Precisely repeatable timing signals for both the integrator and sample and hold circuit are provided by a microprocessor. The device provides low pass filtering without the phase lag normally associated with linear filters. The device allows one set of data to be acquired while the previous set of data is being digitized. The device is especially applicable to analysis of data generated by a spectrophotometer.

Abstract: An optical theta-modulation based analog-to-digital converter having an acousto-optic deflector and an analog-to-digital conversion mask, for fast and flexible analog-to-digital conversion. The acousto-optic deflector deflects an optical beam at an angle corresponding to an input voltage signal having an analog value. The analog-to-digital conversion mask converts the deflected optical beam into N masked optical signals which each corresponds to a respective bit of a digital value representing the analog value of the input signal. Each optical signal is detected by a photodetector and converted into an output voltage signal by a comparator.

Abstract: Optical scanning apparatus which includes an A/D converter control circuit for matching the conversion range of an A/D converter to the range of an analog signal produced by a photo-sensitive detector in response to radiation originating from a radiation source such as a laser. The converter produces a binary overflow signal which signifies whether the analog signal is within or above the conversion range of the converter. Depending on the binary value of the overflow signal, a control signal generator produces either an increasing or decreasing control signal which is returned in a feedback loop to the radiation source to control the radiation intensity or to the converter to adjust its conversion range.

Abstract: A device is provided for converting optical digital signals to electronic analog signals. A light beam is passed through a series of beam splitters. The transmission coefficient of each beam splitter is equal to the reciprocal of the base of the number of the electronic digital input signal. The beam splitters are arranged in series with the light beam so that the reflected portion of the beam is weighted to be proportional to the significance of a place in the binary number corresponding to its beam splitter. The reflected portion of the beam from each beam splitter is separately modulated in response to an input electronic digital signal for the place in the digital number corresponding to its beam splitter. The reflected portions of the beam from each beam splitter are combined and the combined beam is received by a detector which provides an electronic output which is an analog representation of the digital signal.

Abstract: A digital-to-analog conversion circuit capable of preventing a noise produced in a digital system from mixing in an analog output has an input circuit receiving a pulse-code modulated digital signal, a conversion circuit such as a noise shaping circuit for converting the pulse-code modulated digital signal to a pulse wave signal containing analog amplitude information in a time axis direction, a buffer circuit including an electrically insulated coupling circuit such as an optical coupling circuit for transmitting output of the conversion circuit, and an analog output circuit including an analog low-pass filter for delivering out output of the buffer circuit therethrough. A noise generated in a digital system is intercepted by the buffer circuit and is not transmitted further so that mixing of the noise in the analog output circuit is prevented.

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).

Abstract: A digital optical conversion module used to convert an analog signal to a computer compatible digital signal including a voltage-to-frequency converter, frequency offset response circuitry, and an electrical-to-optical converter. Also used in conjunction with the digital optical conversion module is an optical link and an interface at the computer for converting the optical signal back to an electrical signal. Suitable for use in hostile environments having high levels of electromagnetic interference, the conversion module retains high resolution of the analog signal while eliminating the potential for errors due to noise and interference. The module can be used to link analog output scientific equipment such as an electrometer used with a mass spectrometer to a computer.

Abstract: A very high speed optical converter for converting digital signals from Gray code to binary code and vice versa. The converter implements an exclusive-OR function. The converter may be constructed with fiber optic technology, AlGaAs ridge waveguide technology, LiNbO technology and other technologies.

Abstract: A fully optical A/D converter is disclosed in which the difference in light intensity from two outputs of a two-arm interferometer in each channel is detected. The difference in light intensity is varied in accordance with a phase shift in the light passing through one arm of the interferometer. The phase shift is accomplished by the use of a non-linear optical material, the optical properties of which are altered based on the characteristics of an input optical signal to be digitized. Thus, the difference in light intensity corresponds to the magnitude of the input optical signal.

Abstract: Combinatorial (Boolean) logic functions are provided by ultrafast optical logic devices which utilize soliton trapping between two optical signals propagating in a birefringent fiber. The logic devices are three terminal devices having orthogonally polarized soliton input signals and a single output signal. Optically filtering the output from the fiber permits the desired combinatorial logic operation to be performed on the input optical signals. Logic operations include AND, exclusive-OR, NOT, and NOR functions. In operation, the devices exhibit phase insensitivity, low switching energy, high contrast ratio between output logic levels, and cascadability. In one embodiment of the invention, a first optical signal and a second optical signal are optically coupled into the principal axes of a birefringent fiber.

Abstract: An opto-electronic A/D converter comprises an input light source, an input nterferometer, and a plurality of parallel multistable interferometers the optical lengths of which are controlled by respective electrodes, the outputs of the parallel interferometers being converted by photodiodes into electrical signals which are used both to supply a digital output of the converter and as feedback signals to both the respective and an adjacent one of the parallel interferometers.