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Showing papers on "Optical modulator published in 2001"


Book
02 Feb 2001
TL;DR: In this article, a planar waveguide is proposed for optical fiber communications. But it is not shown how it can be used in the case of a single mode fiber and it cannot be shown how to be used with other fiber types.
Abstract: (NOTE: Each chapter concludes with Questions and Problems.) 1. Wave Nature of Light. Light Waves in a Homogeneous Medium. Refractive Index. Group Velocity and Group Index. Magnetic Field, Irradiance and Poynting Vector. Snell's Law and Total Internal Reflection (TIR). Fresnel's Equations. Multiple Interference and Optical Resonators. Goos-Hanchen and Optical Tunneling. Temporal and Spatial Coherence. Diffraction Principles. 2. Dielectric Waveguides and Optical Fibers. Symmetric Planar Dielectric Slab Waveguide. Modal and Waveguide Dispersion in the Planar Waveguide. Step Index Fiber. Numerical Aperture. Dispersion in Single Mode Fibers. Bit-Rate, Dispersion, Electrical and Optical Bandwidth. The Graded Index Optical Fiber. Light Absorption and Scattering. Attenuation in Optical Fibers. Fiber Manufacture. 3. Semiconductor Science and Light Emitting Diodes. Semiconductor Concepts and Energy Bands. Direct and Indirect Bandgap Semiconductors: E-k Diagrams. pn Junction Principles. The pn Junction Band Diagram. Light Emitting Diodes. LED Materials. Heterojunction High Intensity LEDs. LED Characteristics. LEDs for Optical Fiber Communications. 4. Stimulated Emission Devices Lasers. Stimulated Emission and Photon Amplification. Stimulated Emission Rate and Einstein Coefficients. Optical Fiber Amplifiers. Gas Laser: The He-Ne Laser. The Output Spectrum of a Gas Laser. LASER Oscillation Conditions. Principle of the Laser Diode. Heterostructure Laser Diodes. Elementary Laser Diode Characteristics. Steady State Semiconductor Rate Equation. Light Emitters for Optical Fiber Communications. Single Frequency Solid State Lasers. Quantum Well Devices. Vertical Cavity Surface Emitting Lasers (VCSELs). Optical Laser Amplifiers. Holography. 5. Photodetectors. Principle of the pn Junction Photodiode. Ramo's Theorem and External Photocurrent. Absorption Coefficient and Photodiode Materials. Quantum Efficiency and Responsivity. The pin Photodiode. Avalanche Photodiode. Heterojunction Photodiodes. Phototransistors. Photoconductive Detectors and Photoconductive Gain. Noise in Photodetectors. 6. Photovoltaic Devices. Solar Energy Spectrum. Photovoltaic Device Principles. pn Junction Photovoltaic I-V Characteristics. Series Resistance and Equivalent Circuit. Temperature Effects. Solar Cells Materials, Devices and Efficiencies. 7. Polarization and Modulation of Light. Polarization. Light Propagation in an Anisotropic Medium: Birefringence. Birefringent Optical Devices. Optical Activity and Circular Birefringence. Electro-Optic Effects. Integrated Optical Modulators. Acousto-Optic Modulator. Magneto-Optic Effects. Non-Linear Optics and Second Harmonic Generation. Notation and Abbreviations. Index. CD-ROM: Optoelectronics and Photonics Contents.

440 citations


Patent
19 Oct 2001
TL;DR: An optical measurement system for evaluating the surface of a substrate or the thickness and optical characteristics of a thin film layer overlying the substrate includes a light source for generating a light beam, a static polarizing element for polarizing the light beam emanating from the light source, and a measurement system as mentioned in this paper for measuring the light reflected from the substrate location.
Abstract: An optical measurement system for evaluating the surface of a substrate or the thickness and optical characteristics of a thin film layer overlying the substrate includes a light source for generating a light beam, a static polarizing element for polarizing the light beam emanating from the light source, and a measurement system for measuring the light reflected from the substrate location. The measurement system includes a static beam splitting element for splitting the light reflected from the substrate into s-polarized light and p-polarized light. The measurement system further includes two optical sensors for separately measuring the amplitude of the s-polarized light and the intensity of the p-polarized light. A control system analyzes the measured amplitude of the s-polarized light and the p-polarized to determine changes in the topography of substrate or changes in the thickness or optical characteristics of the thin film layer.

138 citations


Patent
10 Aug 2001
TL;DR: In this article, a micro-structured optical waveguide is proposed for optical wavelength conversion, which includes a first optical light source for introducing light into the waveguide in a mode guided along the core, and a second intensity modulated light source that illuminates the sections filled with a non-linear material.
Abstract: In accordance with the invention there is provided an optical wavelength conversion device The conversion device comprises a micro-structured optical waveguide, which includes sections with a non-linear material having an index of refraction which changes as a non-linear function of light intensity The optical waveguide includes a light guiding core region, and the waveguide is dimensioned for providing spatial overlap between the sections filled with the non-linear material and light propagating within the waveguide The conversion device further comprises a first optical light source for introducing light into the waveguide in a mode guided along the core, and a second intensity modulated light source for introducing encoding light into the waveguide in such a manner that it illuminates the sections filled with a non-linear material The second light source has an intensity modulation sufficient to change the refractive index of the non-linear material by an amount sufficient to encode or modulate the light from the first optical light source accordingly, whereby the encoding takes place through the effect of leaking light from the first light source from the inside of the guiding core to the outside of the guiding core The micro-structured optical waveguide may comprisean optical fibre, in which the light from the first light source may be guided by different types of waveguiding principles including total internal reflection or by photonic bandgap effects In an alternative embodiment the micro-structured optical waveguide may comprise an optical planar waveguide The conversion device includes embodiments in which the encoding light from the secondlight source and the light to be encoded or modulated from the first light source are co-propagating, are counter-propagating, or where the encoding light has a propagation direction different to the propagation direction of the light to be encoded According to the invention there is also provided a micro-structured optical waveguide, which may have an axial direction, which waveguideincludes sections that are elongated in the axial direction and comprise a non-linear material having an index of refraction whichchanges as a non-linear function of light intensity This optical waveguide, which may be an optical fibre, includes a light guiding core region, and the waveguide is dimensioned for providing spatial overlap between the sections filled with the non-linear material and light propagating within the waveguide There is furthermore provided an optical switching device and an optical intensity limiting device which may be based on the micro-structured optical waveguide of the invention

134 citations


Book
01 Jan 2001
TL;DR: This book discusses the role of A/D Conversion in Analog-to-Digital Conversion, and some of the approaches taken to achieve this goal.
Abstract: 1. Introduction.- 1.1 The Role of A/D Conversion.- 1.2 Key Technological Challenges.- 1.3 Motivation for Photonic A/D Approaches.- 1.4 Organization of this Book.- 2. Performance Characteristics of Analog-to-Digital Converters.- 2.1 A/D Converter Characteristics.- 2.2 Sampling and Conversion Rate Characteristics.- 2.2.1 Sampling Rate.- 2.2.2 Conversion Rate.- 2.3 Performance Measures.- 2.3.1 Resolution.- 2.3.2 Dynamic Range, SQNR, and SNR Performance Measures..- 2.3.3 Spur-Free Dynamic Range.- 2.4 Performance Degradations.- 2.4.1 Two-Tone Intermodulation Distortion.- 2.4.2 Differential Nonlinearity.- 2.4.3 Integral Nonlinearity.- 2.4.4 Comparator Hysteresis.- 2.4.5 Thermal Noise.- 2.16 Aperture Jitter.- 2.4.7 Comparator Ambiguity.- 2.4.8 Observations.- Summary.- 3. Approaches to Analog-to-Digital Conversion.- 3.1 A/D Converter Coding Schemes.- 3.1.1 Thermometer Coding Scheme.- 3.1.2 Gray Code Coding Scheme.- 3.1.3 Circular Coding Scheme.- 3.2 Nyquist-Rate Converter Architectures.- 3.2.1 Fully Parallel or Flash A/D Conversion.- 3.2.2 Subranging A/D Conversion.- 3.2.3 Folding Architectures.- 3.2.4 Other Parallel Architectures.- 3.2.5 Neural Network Approach to A/D Conversion..- 3.2.6 Full-Search A/D Conversion.- 3.2.7 Successive Approximation A/D Conversion.- 3.3 Oversampled A/D Conversion.- 3.3.1 The Modulator.- 3.3.2 Operation.- 3.3.3 The Digital Postprocessor.- 3.3.4 Oversampled A/D Performance.- 3.4 Parallel Oversampling A/D Conversion.- Summary.- 4. Photonic Devices for Analog-to-Digital Conversion.- 4.1 Mach-Zehnder Interferometers.- 4.2 Optical Waveguide Switches.- 4.2.1 Directional Coupler Waveguide Switches.- 4.2.2 Reversed ?? Directional Coupler..- 4.2.3 Digital Optical Waveguide Switches.- 4.3 Acousto-Optic Devices.- 4.4 Multiple Quantum Well Devices.- 4.4.1 Optical Bistability.- 4.4.2 Optical Subtraction.- 4.4.3 Switching Speed and Energy Requirements.- 4.5 Smart Pixel Technology.- 4.5.1 Monolithic Integration.- 4.5.2 Direct Epitaxy.- 4.5.3 Hybrid Integration.- Summary.- 5. Nyquist-Rate Photonic Analog-to-Digital Conversion.- 5.1 Electro-Optic A/D Conversion Based on a Mach-Zehnder Interferometer.- 5.2 Optical Folding-Flash A/D Converter.- 5.3 Matrix-Multiplication and Beam Deflection.- 5.4 Other Approaches to Photonic A/D Conversion.- Summary.- 6. Oversampled Photonic Analog-to-Digital Conversion.- 6.1 Oversampling Photonic A/D Conversion.- 6.2 Optical Oversampled Modulators.- 6.2.1 The Interferometric Modulator.- 6.2.2 The Noninterferometric Modulator.- 6.3 The Digital Postprocessor.- 6.3.1 Electronic Postprocessing.- 6.3.2 Optoelectronic Postprocessing.- 6.3.3 Observations.- 6.4 Performance Analysis.- 6.4.1 Linear Arithmetic Errors.- 6.4.2 Quantization Noise Spectra.- 6.4.3 Cascade Error Tolerances..- 6.5 Experimental Proof-of-Concept Photonic Modulator Demonstration.- 6.5.1 Noninterferometric Optical Subtraction.- 6.5.2 Experimental Photonic First-Order Oversampled Modulator.- Summary.- 7. Low Resolution, Two-Dimensional Analog-to-Digital Conversion: Digital Image Halftoning.- 7.1 Introduction.- 7.2 Approaches to Halftoning.- 7.3 The Error Diffusion Algorithm.- 7.4 Neural Network Formalism.- 7.4.1 The Hopfield-Type Neural Network.- 7.4.2 Observations.- 7.5 The Error Diffusion Neural Network.- 7.5.1 The Error Diffusion Filter.- 7.5.2 Observations.- 7.6 Quantitative Performance Metrics.- 7.6.1 Power Spectrum Estimation.- 7.6.2 Radially Averaged Power Spectra and Anisotropy.- 7.7 Performance Analysis.- 7.7.1 Floyd-Steinberg Performance Analysis.- 7.7.2 Symmetric Jarvis Performance Analysis.- 7.7.3 Error Diffusion Neural Network Performance Analysis.- 7.8 Extensions to Color.- Summary.- 8. A Photonic-Based Error Diffusion Neural Network.- 8.1 First-Generation CMOS-SEED Error Diffusion Neural Array.- 8.2 Second-Generation CMOS-SEED Error Diffusion Neural Array.- 8.2.1 Detailed Circuit Description.- 8.2.2 Modeling and Simulation.- 8.2.3 Experimental Performance..- 8.2.4 Observations.- 8.3 OPTOCHIP: A 2-D Neural Array Employing Epitaxy-on-Electronics.- 8.3.1 The OPTOCHIP Project.- 8.3.2 Description of Device Architecture.- 8.3.3 Observations.- 8.4 Extensions: A Photonic Error Diffusion Filter.- 8.4.1 Design of the Diffractive Optical Filter.- 8.4.2 Fabrication Error Analysis..- 8.4.3 Experimental Characterization.- 8.4.4 Impact of Fabrication Errors on Halftoning Performance.- Summary.- 9. Photonic A/D Conversion Based on a Fully Connected Distributed Mesh Feedback Architecture.- 9.1 Temporal and Spatial Error Diffusion.- 9.1.1 Spectral Noise Shaping Duality.- 9.1.2 Postprocessing Duality.- 9.1.3 Limit Cycle Oscillation Duality.- 9.1.4 Observations.- 9.2 Spatially Distributed Oversampled A/D Conversion..- 9.3 A 2-D Fully Connected Distributed Mesh Feedback Architecture.- 9.3.1 Mismatch Effects in the Fully Connected Distributed Mesh Feedback Architecture.- 9.4 A/D Conversion Using Spatial Oversampling and Error Diffusion.- 9.4.1 Temporal-to-Spatial Conversion.- 9.4.2 The Two-Dimensional Error Diffusion Neural Network.- 9.4.3 The Postprocessor.- 9.4.4 Spectral Noise Shaping.- 9.4.5 Observations.- 9.5 Three-Dimensional Extensions.- 9.5.1 Space-Time Processing Architectures.- Summary.- 10. Trends in Photonic Analog-to-Digital Conversion.- 10.1 Time-Interleaving A/D Converter Architectures.- 10.1.1 Understanding Time-Interleaved Architectures.- 10.1.2 Mismatch Effects in Time-Interleaved Architectures.- 10.1.3 Block Filter Description of Time-Interleaving.- 10.2 Photonic Channelized A/D Architectures.- 10.2.1 Optical Time-Division Demultiplexing Architectures.- 10.2.2 Wavelength Channelization Architectures.- 10.3 Time-Stretching Using Dispersive Optical Elements.- 10.4 Ultra-Fast Laser Sources with Low Jitter.- 10.5 Novel Optical Sampling Techniques.- 10.6 Broadband Optical Modulators and Switches.- Summary.- References.

106 citations


Patent
03 Apr 2001
TL;DR: In this paper, the authors proposed a method and devices for time division multiplexing of a fiber optic serial Bragg grating sensor array containing more than one Bragg-grating.
Abstract: The present invention provides a method and devices for time division multiplexing of a fiber optic serial Bragg grating sensor array containing more than one Bragg grating. The device provides a pulse read-out system that allows for a reduction in system noise and an increase in sensor resolution and flexibility. In one aspect the optical signals reflected from the Bragg grating sensor array are gated by an electronically controlled optical modulator before any wavelength measurement is performed to determine the sensor information. This offers significant advantages since the sensor information is encoded into the wavelength of the optical signal and not its intensity. Therefore the sensor signal information is not distorted by the gating. Since the gating or switching of the optical modulator is performed on the optical signal, the speed of the electronic processing needs only to be performed at the speed of variation of the sensor information and the choice of methods of wavelength measurement is not influenced by the gating action. The device may include one or more optical amplifiers that provide the ability to demultiplex the reflected signals electronically.

97 citations


Patent
21 Dec 2001
TL;DR: In this paper, a control signal applied to a modulator optical component through the modulator control component alters the round-trip optical loss of the circumferential-mode resonator, thereby altering the transmission of a resonant optical signal through the transmission fiber-optic waveguide.
Abstract: A resonant optical modulator comprises a transmission fiber-optic waveguide, a circumferential-mode optical resonator transverse-coupled thereto, a modulator optical component transverse-coupled to the circumferential-mode resonator, and a modulator control component. A control signal applied to the modulator optical component through the modulator control component alters the round-trip optical loss of the circumferential-mode resonator, thereby altering the transmission of a resonant optical signal through the transmission fiber-optic waveguide. The modulator optical element may comprise an open waveguide or a closed waveguide (i.e., resonator). The resonator round-trip optical loss may be altered by altering the optical absorption/scattering of the modulator optical component, by altering the amount of optical power transfer between the resonator and the modulator optical component, or by altering an optical resonance frequency of a resonant modulator optical component.

94 citations


Patent
03 Jul 2001
TL;DR: In this article, high-impedance optical electrodes modulate light in response to a life-form bio-potential and then convert the modulated light to an electrical signal that provides traditional EEG and EEC type output.
Abstract: High-impedance optical electrodes modulate light in response to a life-form bio-potential and then converts the modulated light to an electrical signal that provides traditional EEG and EEC type output. Light splitters are used to provide multiple electrodes and an electronic reference source. A pilot tone is used to achieve high sensitivity and synchronize multiple units while an optical phase-shift modulator is used to reduce optical noise.

82 citations


Patent
31 Oct 2001
TL;DR: In this paper, an apparatus for optical coherence reflectometry is described, in which the light reflected from the sample is amplified without correspondingly amplifying the light in the reference light field.
Abstract: The present invention relates to an apparatus for optical coherence reflectometry, in particular for optical coherence tomography, wherein the apparatus for optical coherence reflectometry comprises a wavelength scanning laser source for providing a light signal, and splitting means for dividing said light signal into a sample light field and a reference light field, wherein the sample light field is directed to the sample being measured, and the light reflected from the sample is amplified without correspondingly amplifying the light reflected in the reference light field. Thereby, it is possible to direct substantially all light energy from the first reflected light field to the detectors, and to obtain fully the utilisation of the amplification of the first reflected light field. The optical amplifier inserted in the sample reflected light field is different from the source so that the effect of the light source may be regulated independent of the degree of amplification. In particular when using the apparatus in coherent optical FMCW reflectometry certain safety regulations for the power density towards the sample has to be observed to reduce the risk of damages to the sample under examination, such as biological tissue. The apparatus may be used for a variety of purposes, in particular for obtaining optical biopsies of transparent as well as non-transparent tissues.

79 citations


Journal ArticleDOI
TL;DR: In this article, a 10-Gb/s on-off-keying baseband signal and a 60-GHz RF signal with 155-Mb/s differential-phase-shiftkeying (DPSK) data on a single wavelength is investigated.
Abstract: A simultaneous modulation and fiber-optic transmission of a 10-Gb/s baseband signal and a 60-GHz RF signal with 155-Mb/s differential-phase-shift-keying (DPSK) data on a single wavelength is investigated. To the authors' knowledge, it is experimentally demonstrated for the first time that both a 10-Gb/s on-off-keying baseband signal and a 60-GHz RF signal with 155-Mb/s DPSK data are simultaneously modulated with a single optical modulator and transmitted over 40-km-long dispersion-shifted fiber (DSF). There exists the received optical power capable of achieving a bit error rate of 10/sup -9/ simultaneously for both the RF and baseband signals. The degradations due to the nonlinearity of the electroabsorption modulator for the baseband and RF signals are also investigated theoretically and clarified numerically.

71 citations


Patent
James A. Walker1
17 Aug 2001
TL;DR: In this paper, the authors describe an optical modulator with a sense element configured to measure a characteristic associated with the modulator window, and a drive electrode that adjusts a portion of the optical modulation window to attenuate light passing there through.
Abstract: An optical modulator having an optical modulator window coupled to a substrate and a method of manufacture thereof. In one embodiment, the optical modulator includes at least one drive electrode that adjusts a portion of the optical modulator window to attenuate light passing therethrough. The optical modulator further includes a sense element configured to measure a characteristic associated with the optical modulator window.

71 citations


Journal ArticleDOI
TL;DR: In this paper, a method for measuring the chirp parameters and optical responses of Mach-Zehnder-type optical modulators by using an optical spectrum analyzer is described.

Journal ArticleDOI
TL;DR: A compact experimental system is constructed that uses a 635-nm diode laser in which a fixed encrypted 0/pi binary phase mask is decrypted by a binary phase key produced electronically on the spatial light modulator.
Abstract: We present a system for the implementation of phase-only optical decryption of an encrypted fixed phase mask. We achieve decryption by superimposing a decrypting phase key, implemented on a phase-only spatial light modulator with an encrypted phase mask in two equivalent image planes in an optical system. The decrypted phase information is retrieved by the generalized phase-contrast technique. We have constructed a compact experimental system that uses a 635-nm diode laser in which a fixed encrypted 0/pi binary phase mask is decrypted by a binary phase key produced electronically on the spatial light modulator. The key is aligned by electronic scrolling of its position with respect to the mask.

Patent
28 Nov 2001
TL;DR: In this article, a magnification-varying optical system for similarly changing the entire size of a secondary multiple light source is arranged in an optical path between a first optical integrator for forming a first multiple-light source on the basis of a light beam from a light source and a second one having light sources of a larger number.
Abstract: An illumination optical apparatus successfully realizes mutually different illumination conditions in orthogonal two directions on an illumination objective plane. A magnification-varying optical system for similarly changing the entire size of a secondary multiple light source is arranged in an optical path between a first optical integrator for forming a first multiple light source on the basis of a light beam from a light source and a second optical integrator for forming the second multiple light source having light sources of a larger number on the basis of a light beam from the first multiple light source. The apparatus further comprises an aspect ratio-changing element for changing the aspect ratio of the incoming light beam in order to change the angle of incidence of the incoming light beam into the first optical integrator in a predetermined direction.

Journal ArticleDOI
TL;DR: In this article, the authors demonstrate the generation of 5.0-fs optical pulses (2.5 µJ, 1-kHz repetition rate), using only a spatial light modulator for phase compensation.
Abstract: We experimentally demonstrate the generation of 5.0-fs optical pulses (2.5 µJ, 1-kHz repetition rate), using only a spatial light modulator for phase compensation. Pulse compression of the broadband pulse (500–1000 nm) from an argon-filled capillary fiber is achieved with a liquid-crystal spatial light modulator without any prechirp compensation. The output pulse width is found to be 4.1 fs by a fringe-resolved autocorrelator fitted with a transform-limited pulse and to be 5.0 fs by second-harmonic generation frequency-resolved optical gating with marginal correction. It is to our knowledge the shortest pulse ever generated by use of only a spatial light modulator for phase compensation.

Patent
09 Feb 2001
TL;DR: In this paper, an optical interconnection is used to optically interconnect a waveguide-based optical modulator through the insulating layer and back side of the semiconductor substrate of the integrated circuit die.
Abstract: A method and an apparatus providing an optical interconnection in an integrated circuit die. In one embodiment, an optical interconnection is used to optically interconnect a waveguide-based optical modulator through the insulating layer and back side of the semiconductor substrate of the integrated circuit die. In one embodiment, an insulating oxide layer is disposed between a semiconductor waveguide optical modulator and the back side of the semiconductor substrate. Optical conduits are disposed in the insulating oxide layer at the locations where light enters and exits the semiconductor waveguide optical modulator. In one embodiment, the optical conduits have indexes of refraction substantially equal to the indexes of refraction of the semiconductor substrate and the semiconductor waveguide optical modulator. Thus, attenuation of the light used to optically couple the semiconductor waveguide optical modulator through the back side of the semiconductor substrate is reduced.

Patent
27 Jul 2001
TL;DR: In this paper, the first and second optical elements are arranged in either a Keplerian or Galilean configuration, and the aspheric surface of the second optical element is related to the first optical element by a ray-tracing function that maps substantially all of an input light beam that is incident on the first one to a collimated output light beam from the second one.
Abstract: An optical beam transformation system includes a first and a second optical element, each of which has a non-reentrant surface. The system transforms a substantially non-uniform optical input beam (such as a Gaussian) to a substantially uniform output beam. The first and second optical elements are arranged in either a Keplerian or Galilean configuration. The aspheric surface of the second optical element is related to the aspheric surface of the first optical element by a ray-tracing function that maps substantially all of an input light beam that is incident on the first optical element to a collimated output light beam that is output from the second optical element. Preferably, the output light beam has a Fermi-Dirac intensity distribution, and the ray-tracing function maps the input light beam to the output beam out to the (1/e)6 intensity radius of the input light beam.

Patent
02 Feb 2001
TL;DR: In this article, a low-frequency superimposing unit superimposes a prescribed lowfrequency signal on the modulator driving voltage signal, and an operating point controller controls the operating point of the optical modulator by detecting operating point drift.
Abstract: An optical modulator having a voltage-optical output characteristic in which optical output varies periodically with respect to a voltage value of an electrical drive signal is driven by a modulator driving voltage signal, which has an amplitude of 2·Vπ between two light-emission culminations or two light extinction culminations of the voltage-optical output characteristic. A low-frequency superimposing unit superimposes a prescribed low-frequency signal on the modulator driving voltage signal, and an operating-point controller controls the operating point of the optical modulator by detecting operating-point drift of the optical modulator based upon the low-frequency signal component contained in an optical signal output from the optical modulator and controlling the bias voltage of the optical modulator in dependence upon the drift of the operating point of the optical modulator.

Journal ArticleDOI
TL;DR: In this paper, a phase modulator driven by a single electrical non-return-to-zero signal and an optical delay interferometer is used for variable duty cycle return-tozero (RZ) modulation.
Abstract: We experimentally demonstrate and discuss a new technique for variable duty cycle return-to-zero (RZ) modulation, employing a phase modulator driven by a single electrical nonreturn-to-zero signal, and an optical delay interferometer. Unlike other methods for generating RZ, no synchronization between two electrical driving signals is needed.

Patent
19 Jan 2001
TL;DR: In this article, the phase shift amount of the electric clock signal is controlled to maximize an output from the photo detector, where a dither signal is used in the control of phase shift, more than the optical modulator may be employed, and/or more than color light source may be used.
Abstract: Detection of an optical pulse position uses an optical pulse string with a determined repetitive ratio and an electric clock signal with a same frequency as the repetitive ratio of the optical pulse string. A phase of the electric clock signal oscillator is shifted and supplied to an optical modulator. The optical modulator modulates the optical pulse string based on the electric clock signal and outputs a modulated optical signal. A photo detector converts the modulated optical signal output from the optical modulator to an electric signal. The phase shift amount of the electric clock signal is controlled to maximize an output from the photo detector. Additionally, a dither signal may be used in the control of the phase shift, more than the optical modulator may be employed, and/or more than color light source may be employed. The use of at least one of feed forward and feedback control provided by maximizing an output of the photo detector allows an optical pulse having a short width to be realized.

Journal ArticleDOI
Yi Jiang1, Zhuangqi Cao1, Guang Chen1, Xiaoming Dou1, Yingli Chen1 
TL;DR: In this paper, an improved electro-optic (EO) polymer light modulator based on attenuated-total internal reflection (ATR) is demonstrated, which consists of a prism-metal-polymer-metal multilayer structure.
Abstract: An improved electro-optic (EO) polymer light modulator based on attenuated-total-internal-reflection (ATR) is demonstrated. The modulator consists of a prism–metal–EO-polymer–metal multilayer structure. An applied electric field across the EO polymer layer electrically modulates the energy coupling efficiency of incoming light into guided wave resonance at fixed angles. Compared with conventional ATR modulators based on surface plasmon resonance, the driving voltage for this modulator has been greatly reduced because of the newly chosen working interior angle. It also offers advantages in terms of insertion loss and aperture size over other techniques for the amplitude modulation of a collimated light beam.

Journal ArticleDOI
TL;DR: In this article, a resonant-type LiNbO/sub 3/ optical modulator with symmetric stubs and modulating electrodes was investigated and the enhancement factor of the fabricated modulator was 3.41 at 10 GHz.
Abstract: A resonant-type LiNbO/sub 3/ optical modulator with symmetric stubs and modulating electrodes was investigated. Modulation efficiency was enhanced by the resonance of the modulating electrode. The enhancement factor of the fabricated modulator was 3.41 at 10 GHz.

Patent
21 Sep 2001
TL;DR: In this article, a projected light quantity controller is adapted to control the operation of projected light of the projected light and that of modulating the write signal of a write signal processor on the basis of the brightness level of the input image signal.
Abstract: A projection type image-display apparatus includes a write signal processor for modulating the write signal transmitted to an optical modulator, a projected light quantity controlling for controlling the quantity of light transmitted or reflected by the optical modulator, and a control signal generator for controlling the write signal processor and the projected light quantity controller. The control signal generator is adapted to control the operation of controlling the quantity of projected light of the projected light quantity controller and that of modulating the write signal of the write signal processor on the basis of the brightness level of the input image signal.

Journal ArticleDOI
TL;DR: In this article, a single-sideband suppressed-carrier modulator design using a standard single-electrode Mach-Zehnder electrooptic modulator is presented.
Abstract: This letter demonstrates a novel optical single-sideband suppressed-carrier modulator design using a standard single-electrode Mach-Zehnder electrooptic modulator bidirectionally. It is proven that its single-sideband operation is insensitive to bias and optical modulation depth. Up to 25 dB of sideband suppression and 14 dB of optical carrier attenuation are obtained in experiments at microwave modulation frequencies. In addition, suppression of dispersion-induced power fading is demonstrated in a link with a total dispersion of 2691 ps/nm.

Patent
07 Mar 2001
TL;DR: In this paper, a modulated light source is defined as a light source emitting an inherently modulated output, or a separate optical modulator and a continuous wave, modulated, or pulsed light source configured to impose a modulation in the output of the light source.
Abstract: Methods and apparatus directed to using modulation to substantially improve detection limits in optical imaging, and to substantially improve the performance of various optical imaging systems. Such modulation is achieved using a modulated light source (40), a modulation frequency reference (42), a detector (10), and a demodulator (46). The modulated light source may comprise a light source emitting an inherently modulated output; or, this modulated light source may comprise a separate optical modulator and a continuous wave, modulated, or pulsed light source configured to impose a modulation in the output of light source. Methods for imaging are also disclosed.

Patent
07 May 2001
TL;DR: In this paper, the first and second light modulation regions are positioned in series in a moving direction of the scale, and the second modality region moves integrally with the first light modulation region with movement of scale.
Abstract: There is disclosed an optical encoder in which a scale can be displaced to cross a first light beam emitted from a first light source, and has a first light modulation region formed of a predetermined-period optical pattern irradiated with the first light beam to generate a diffraction pattern. First photodetector has a light receiving surface for receiving the first light beam transmitted through the first light modulation region of the scale, and has a single or a plurality of light receiving element group formed at a predetermined interval corresponding to the diffraction pattern. A second light modulation region modulates optical properties of the second light beam emitted from a second light source. Second photodetector receives the second light beam whose optical properties are modulated by the second light modulation region. The first and second light modulation regions are positioned in series in a moving direction of the scale, and the second light modulation region moves integrally with the first light modulation region with movement of the scale.

Patent
17 Sep 2001
TL;DR: In this paper, a travelling wave-type optical modulator has a substrate made of an electro-optic material, optical waveguides fabricated on the top surface of the substrate, and electrodes for modulating an optical wave through the optical waveguide.
Abstract: A travelling wave-type optical modulator has a substrate made of an electro-optic material, optical waveguides fabricated on the top surface of the substrate, and electrodes for modulating an optical wave through the optical waveguide. The substrate is partially thinned from the bottom surface of the substrate to form a first thinned portion and a second thinned portion so that the thickness of the first thinned portion is set to be larger than the thickness of the second thinned portion, and the optical waveguide is positioned in the first thinned portion.

Patent
11 Jun 2001
TL;DR: In this paper, the identification waveform detector detects when the waveform starts to change, and it is possible to obtain synchronization between an incidence side and an exit side of the optical fiber.
Abstract: An apparatus for measuring optical characteristics includes a variable-wavelength light source for generating a variable-wavelength light, having an identification waveform when the wavelength changes, the identification waveform being distinguishable from a normal waveform before and after the wavelength changes, an optical modulator for modulating the variable-wavelength light at a predetermined frequency and inputting it to an optical fiber; and an identification waveform detector for detecting the identification waveform of light transmitted through the optical fiber, wherein since the identification waveform detector detects when the waveform starts to change, it is possible to obtain synchronization between an incidence side and an exit side of the optical fiber. Accordingly, it is possible to obtain synchronization between an incidence side and an exit side of a device-under-test even if the wavelength of light source is continuously swept, whereby characteristics such as chromatic dispersion and the like can be measured.

Patent
06 Jul 2001
TL;DR: In this article, the shape of a spectrum of a multi-wavelength light is controlled so that predetermined RIN and SNR can be obtained in accordance with transmission system parameters (the type and distance of optical fibers, the number of repeaters).
Abstract: With respect to the relative intensity noise (RIN) for inputs to an optical modulator or the signal-to-noise ratio (SNR) for outputs therefrom, the optical modulator modulating coherent lights of different wavelengths obtained by slicing a spectrum of the multi-wavelength light, the shape of a spectrum of a multi-wavelength light is controlled so that predetermined RIN and SNR can be obtained in accordance with transmission system parameters (the type and distance of optical fibers, the number of repeaters), thus enabling design meeting a performance specification for a conventional transmission section using semiconductor lasers.

Patent
Motoyuki Fujimori1
12 Sep 2001
TL;DR: An optical modulation device which can facilitate a reduction in size of a device and prevent overheating of the optical modulation devices, and a projection display device utilizing the optical modulation device are provided in this article.
Abstract: An optical modulation device which can facilitate a reduction in size of a device and prevent overheating of the optical modulation device, and a projection display device utilizing the optical modulation device are provided. In the optical modulation device, sapphire glasses are affixed to the light-incident side and the light-emitting side surfaces of liquid crystal panels which respectively modulates light of three colors of red, green, and blue emitted from a light source according to image information. Therefore, heat generated on optical modulation devices can be discharged, so that overheating of the optical modulation devices can be prevented, and a reduction in size can be achieved. In addition, since the sapphire glass is difficult to scratch, it becomes easy-to-handle, thereby facilitating the management of the optical modulation devices.

Journal ArticleDOI
TL;DR: In this paper, the authors proposed a novel optical modulation system for generating high-order harmonics, by using two filters placed at the optical input and output ports of an optical modulator.
Abstract: The authors propose a novel optical modulation system for generating high-order harmonics, by using two filters placed at the optical input and output ports of an optical modulator. By reciprocating optical modulation at 30 GHz, the sixth-order harmonic, whose frequency is shifted by 180 GHz, is generated effectively.