Showing papers on "Optical fiber published in 1992"

Fiber-Optic Communication Systems

Abstract: Preface. 1 Introduction. 1.1 Historical Perspective. 1.2 Basic Concepts. 1.3 Optical Communication Systems. 1.4 Lightwave System Components. Problems. References. 2 Optical Fibers. 2.1 Geometrical-Optics Description. 2.2 Wave Propagation. 2.3 Dispersion in Single-Mode Fibers. 2.4 Dispersion-Induced Limitations. 2.5 Fiber Losses. 2.6 Nonlinear Optical Effects. 2.7 Fiber Design and Fabrication. Problems. References. 3 Optical Transmitters. 3.1 Semiconductor Laser Physics. 3.2 Single-Mode Semiconductor Lasers. 3.3 Laser Characteristics. 3.4 Optical Signal Generation. 3.5 Light-Emitting Diodes. 3.6 Transmitter Design. Problems. References. 4 Optical Receivers. 4.1 Basic Concepts. 4.2 Common Photodetectors. 4.3 Receiver Design. 4.4 Receiver Noise. 4.5 Coherent Detection. 4.6 Receiver Sensitivity. 4.7 Sensitivity Degradation. 4.8 Receiver Performance. Problems. References. 5 Lightwave Systems. 5.1 System Architectures. 5.2 Design Guidelines. 5.3 Long-Haul Systems. 5.4 Sources of Power Penalty. 5.5 Forward Error Correction. 5.6 Computer-Aided Design. Problems. References. 6 Multichannel Systems. 6.1 WDM Lightwave Systems. 6.2 WDM Components. 6.3 System Performance Issues. 6.4 Time-Division Multiplexing. 6.5 Subcarrier Multiplexing. 6.6 Code-Division Multiplexing. Problems. References. 7 Loss Management. 7.1 Compensation of Fiber Losses. 7.2 Erbium-Doped Fiber Amplifiers. 7.3 Raman Amplifiers. 7.4 Optical Signal-To-Noise Ratio. 7.5 Electrical Signal-To-Noise Ratio. 7.6 Receiver Sensitivity and Q Factor. 7.7 Role of Dispersive and Nonlinear Effects. 7.8 Periodically Amplified Lightwave Systems. Problems. References. 8 Dispersion Management. 8.1 Dispersion Problem and Its Solution. 8.2 Dispersion-Compensating Fibers. 8.3 Fiber Bragg Gratings. 8.4 Dispersion-Equalizing Filters. 8.5 Optical Phase Conjugation. 8.6 Channels at High Bit Rates. 8.7 Electronic Dispersion Compensation. Problems. References. 9 Control of Nonlinear Effects. 9.1 Impact of Fiber Nonlinearity. 9.2 Solitons in Optical Fibers. 9.3 Dispersion-Managed Solitons. 9.4 Pseudo-linear Lightwave Systems. 9.5 Control of Intrachannel Nonlinear Effects. Problems. References. 10 Advanced Lightwave Systems. 10.1 Advanced Modulation Formats. 10.2 Demodulation Schemes. 10.3 Shot Noise and Bit-Error Rate. 10.4 Sensitivity Degradation Mechanisms. 10.5 Impact of Nonlinear Effects. 10.6 Recent Progress. 10.7 Ultimate Channel Capacity. Problems. References. 11 Optical Signal Processing. 11.1 Nonlinear Techniques and Devices. 11.2 All-Optical Flip-Flops. 11.3 Wavelength Converters. 11.4 Ultrafast Optical Switching. 11.5 Optical Regenerators. Problems. References. A System of Units. B Acronyms. C General Formula for Pulse Broadening. D Software Package.

The shape of fiber tapers

Abstract: A model for the shape of optical fiber tapers, formed by stretching a fiber in a heat source of varying length, is presented. Simple assumptions avoid any need for the techniques of fluid mechanics. It is found that any decreasing shape of taper can be produced. The procedure for calculating the hot-zone length variation required to produce a given shape of taper is described, and is used to indicate how an optical adiabatic taper can be made. A traveling burner tapering system is capable of realizing the model's prediction, and a complete practical procedure for the formation of fiber tapers with any reasonable shape is thus presented. >

High-resolution fibre-grating based strain sensor with interferometric wavelength-shift detection

Abstract: A technique for the detection of dynamic strain induced wavelength shifts in fibre Bragg grating sensors is reported that is based on an unbalanced-interferometer wavelength discriminator, which is capable of subnanostrain resolution (0.6 ne/√(Hz) at 500 Hz) sensing.

Four-wave mixing in an optical fiber in the zero-dispersion wavelength region

Abstract: Fiber four-wave mixing (FWM) in the zero-dispersion wavelength region is described. The phase-matching characteristics are studied in the wavelength region where the first-order chromatic dispersion is zero. The results show that the phase-matching condition is satisfied and FWM light is efficiently generated at particular combinations of input light wavelengths. It is also shown that the deviation of the zero-dispersion wavelength along the fiber length plays an important role in FWM behavior. >

Polarization multiplexing with solitons

Abstract: It is shown both analytically and with numerical simulation, and confirmed experimentally in transmission over distances up to approximately 10000 km, that solitons maintain a high degree of polarization over an ultra-long distance transmission system consisting of birefringent dispersion-shifted fiber segments and erbium amplifiers. Based on that fact, the authors propose a polarization/time division multiplexing technique which should allow the single-wavelength bit-rate capacity of an ultra-long distance soliton transmission system to be doubled with little or no significant increase in bit error rate. >

Fiber Optic Networks

Abstract: Fibre optic networks applications and their requirements fibres, couplers and taps tunable filters laser diodes lightwave amplifiers modulation and remodulation techniques detection and demodulation of optical signals subcarrier (wavelength x frequency) techniques frequency stability and its control organizing the system topologically layered architectures in lightwave networks multiaccess, switching and performance operating third generation links operating third generation multipoints operating third generation networks

A passive wavelength demodulation system for guided-wave Bragg grating sensors

Abstract: A novel, passive, and self-referencing wavelength detection system (WDS) that measures the wavelength of the narrowband back-reflected spectrum of guided-wave Bragg gratings is described. This letter also reports on the use of such a detection system with fiber-optic Bragg gratings used as absolute strain sensors. The wavelength detection system demonstrated a 1% strain resolution of the total strain measurement range. >

Laser light irradiation apparatus

Abstract: A laser light irradiation apparatus used for medical treatment of living tissue. According to a preferred embodiment, the apparatus comprises a probe and a plural number of optical fibers. The optical fibers surround the axis of the probe. Laser light goes through each optical fiber and is applied to the probe. Then, the laser light is emitted from the probe to be uniformly irradiate the tissues, and if desired, against the tissues over a broad area. Further, a guide wire and/or a lead wire for detecting a temperature can be placed so as to be coaxial with the probe. Therefore, a perforation of a normal part of the blood vessel can be prevented.

Submicrometer intracellular chemical optical fiber sensors

Abstract: A thousandfold miniaturization of immobilized optical fiber sensors, a millionfold or more sample reduction, and at least a hundredfold shorter response time, all simultaneously, were achieved by combining nanofabricated optical fiber tips with near-field photopolymerization. Specifically, pH optical fiber sensors were prepared with internal calibration, making use of the differences in both fluorescence and absorption of the acidic and basic dye species. The submicrometer sensors have excellent detection limits, as well as photostability, reversibility, and millisecond response times. Successful applications include intracellular and intraembryonic measurements. Potential applications include spatially and temporally resolved chemical analysis and kinetics inside single biological cells and their substructures.

Wavelength conversion experiment using fiber four-wave mixing

Abstract: Wavelength conversion using fiber four-wave mixing in an optical fiber is demonstrated. Utilizing the wavelength region around the zero-dispersion wavelength of a fiber, 622 Mbt/s FSK signal light is converted from 1555.2 to 1547.6 nm with a conversion efficiency of -24 dB. >

Small signal analysis for dispersive optical fiber communication systems

Abstract: A small signal analysis for analyzing the conversion between intensity and phase modulation or noise in a dispersive fiber is given. Using this theory the small signal response of laser diodes with respect to intensity and phase modulation in dispersive optical fibers is derived. Guidelines are also given for considerably reducing the intensity noise if a fiber with a suitable dispersion is used. All analytical calculations are compared with numerical simulations and good agreement is achieved. >

Cerenkov light generated in optical fibres and other light pipes irradiated by electron beams

Abstract: The use of a small plastic scintillator coupled to an optical fibre bundle light pipe as a means for the dosimetry of radiotherapy X-ray or electron beams in a phantom has been studied. Under such conditions, some light is generated by the direct action of the radiation on the optical fibres themselves, and this 'background' signal must be correctly accounted for. In the present study, electron beams were incident on fused silica optical fibres and other light pipes made of polymethylmethacrylate (PMMA), polystyrene and water. The observed light signal generated in all cases was found to depend strongly on the angle between the electron direction and the light pipe axis, and to correlate well with the angular characteristics uniquely associated with Cerenkov radiation. The use of a parallel fibre bundle light pipe, identical to the one that carries light from the scintillator, offers a suitable means of generating a similar background Cerenkov light signal that can be subtracted to obtain the output from the scintillation dosimeter alone.

Armored fiber optic cables

Abstract: An armored fiber optic cable is disclosed having both fiber optics and ar wires located outside the cable core in position where the fiber optics experience low strain when the cable is under stress. In one embodiment, metal armor wires and optical fibers embedded in metal tubes are arrayed in one or more layers about and outside the cable core. In another embodiment, KEVLAR armor wires and optical fibers embedded within a hard composite shell are arrayed in one or more layers about and outside the cable core, and a layer of KEVLAR armor is provided surrounding the one or more layers. In each of the embodiments the strains that the fiber optics experience due to core stresses and due to core residual strain is materially reduced over the heretofore known armored fiber optic cables.

Dispersion compensating devices and systems

Abstract: Disclosed is a family of dispersion compensating optical fibers that are adapted for use with conventional single-mode transmission fibers that are optimized for zero dispersion operation at a wavelength in the range from 1290 nm to 1330 nm to form a transmission link suitable for low dispersion operation in the 1520-1565 nm wavelength window. The dispersion compensating fibers are capable of providing a dispersion more negative than -20 ps/nm-km and attenuation less than 1 dB/km at wavelengths in the 1520-1565 nm region. Certain of the dispersion compensating fibers also exhibit a dispersion versus wavelength relationship having a negative slope in the 1520-1565 nm region, to compensate for the dispersion versus wavelength slope of the transmission fiber. The dispersion compensating fiber can be advantageously combined with a fiber amplifier to form a compensator that is adapted to overcome attenuation introduced into the system by the dispersion compensating fiber. In one embodiment, the dispersion compensating fiber is also a distributed fiber amplifier.

Method of fabricating Bragg gratings using a silica glass phase grating mask and mask used by same

Abstract: An index grating is imprinted in the core of an optical fiber using a specially designed silica glass phase grating mask The phase mask is held in close proximity to the optical fiber Laser irradiation of the phase mask with ultraviolet light at normal incidence imprints (photoinduces) into the optical fiber core the interference pattern created by the phase mask

Tissue penetrating apparatus and methods

Abstract: A tissue penetrating apparatus including a surgical appliance having a sharp tip for penetrating tissue, a first optical element for emitting one or more selected monochromatic wavelengths of light, and a second optical element for sensing light corresponding to the one or more selected monochromatic wavelengths of light. The first and second optical elements are optical transmission fibers secured to the appliance proximate to the tip so that one fiber passes one or more monochromatic wavelengths of light into the tissue to be penetrated, and the other fiber passes the light sensed to a light detector. A control circuit is used to illuminate the one or more light sources to emit light out one of the first and second optical fibers, and to provide an electrical signal corresponding to the light sensed at the other of the first and second optical fibers. The electrical signal includes sensed light at each of the monochromatic wavelengths of light emitted, and sensed light in the absence of emitted light. An analysis circuit or a microprocessor based device may be used for processing the electrical signals and determining when the appliance tip has entered a body cavity. An annunciator is actuated to indicate the relative extent of passage through the tissue and when penetration has occurred.

Multifiber optical connector plug with low reflection and low insertion loss

Abstract: A multifiber optical connector plug capable of realizing low reflection and low insertion loss, without using the refractive index matching material. The multifiber optical connector plug includes a connector plug member made of a plastic material, having a connecting facet on which endfaces of the optical fibers to be connected with other optical fibers are arranged in a transverse direction between the guide pin insertion holes, with the endfaces of the optical fibers projecting out of the connecting facet, the connecting facet being inclined with respect to an axial direction along optical axes of the optical fibers by an angle which is larger than a total reflection critical angle of light beams transmitted through the optical fibers. The connecting facet may have a flat surface shape or a convex ellipsoidal surface shape. A multifiber optical connector can be formed by a pair of such multifiber optical connector plugs with spring member for pressing the multifiber optical connector plugs toward each other in the axial direction and guide pins for aligning the multifiber optical connector plugs.

A Fabry-Perot microinterferometer for visible wavelengths

Abstract: The authors report on their efforts to develop a silicon-based microinterferometer for optical applications in the visible spectral region using micromachining fabrication techniques. The interferometer is formed by two parallel dielectric mirrors supported on membranes which are electrostatically deflected for wavelength control. A simplified two-wafer fabrication process was designed and investigated. They obtained 250 nm membrane deflection for an applied voltage of 100 V. Hafnium dioxide-silicon dioxide dielectric mirrors with high reflectivity and low stress were fabricated on membrane supports and also free-standing. Anticipated applications include microinstrument spectroscopy systems for atomic absorption, ellipsometry, imaging, optical fiber communications, and general spectrophotometer uses as well as accelerometry. >

Side-polished fibers.

Abstract: We report a reproducible technique of making side-polished fibers by embedding fibers in silicon V grooves and by polishing them mechanically. Details of V grooves and polishing techniques are described. The attenuation characteristics of polished fibers were measured by a liquid-drop method; the results are in excellent agreement with existing theoretical predictions. To facilitate comparisons, we cast expressions for the attenuation constant in terms of three generalized parameters: the V and b parameters for the fiber and a new generalized parameter V(ex) for the external medium. By using these generalized parameters, we can study the effects of the external medium on the attenuation constant of side-polished fibers in great detail, including in particular the region where the attenuation changes precipitously.

Continuous gradient cylindrical diffusion tip for optical fibers and method for using

Abstract: A diffuser tip for a fiber optic or array of fibers having a proximal end which abuts against the tip of the fiber optic or array of fibers. The diffuser tip has a cylindrical center core of transparent elastomer which contains scattering centers embedded therein. The scattering centers are distributed within the core so that the concentration of scatterers increases continuously in a direction from the proximal end of the diffuser tip to the distal end of the diffuser tip.

Optical Guided Waves and Devices

Abstract: Overview electromagnetic fields and plane waves material effects the optics of beams reflection and refraction at a single interface the slab waveguide planar waveguide integrated optics optical fibres and fibre devices coupled mode devices optoelectronic interactions in semiconductors optoelectronic devices optic device fabrication systems and applications.

Fabry-Perot optical sensing device for measuring a physical parameter

Abstract: The optical sensing device and the method thereof are for measuring a physical parameter The device is to be connected to a light source which generates a multiple frequency light signal having predetermined spectral characteristics The device comprises a Fabry-Perot interferometer through which the light signal is passed, an optical focusing device for focusing at least a portion of the light signal outgoing from the Fabry-Perot interferometer, and a Fizeau interferometer through which the focused light signal is passed The Fabry-Perot interferometer includes two semi-reflecting mirrors substantially parallel to one another and spaced by a given distance so as to define a Fabry-Perot cavity having transmittance or reflectance properties which are affected by the physical parameter and which cause the spectral properties of the light signal to vary in response to the physical parameter The Fabry-Perot interferometer is provided with at least one multimode optical fiber for transmitting the light signal into the Fabry-Perot cavity and for collecting the portion of the light signal outgoing thereof The Fizeau interferometer includes an optical wedge forming a wedge-profiled Fizeau cavity from which exits a spatially-spread light signal indicative of the transmittance or reflectance properties of the Fabry-Perot interferometer The physical parameter can be determined by means of the spatially-spread light signal

High-resolution reflectometry in biological tissues

Abstract: Optical low-coherence reflectometry is applied for the first time to our knowledge to investigate diffusive biological tissues with a single-mode fiber probe. Samples of fresh arteries are studied, using the backscattered light from the tissue. The probed volume in the vicinity of the fiber tip is estimated to be below 6.7 × 10−10 cm3. This noninvasive method allows one to determine optical parameters, such as the index of refraction and the transmission properties, and the tissue thickness.

Polarization effect on four-wave mixing efficiency in a single-mode fiber

Abstract: Four-wave mixing in a single-mode fiber is studied for general polarization states in input lights. A theory is developed for fiber four-wave mixing where the polarization states of input light are various and they change randomly when propagating through a fiber line. The results show that intensity beating between the propagating lights plays an important role in four-wave mixing efficiency in a fiber. Experimental results support the theoretical treatment. >

Short single frequency erbium-doped fibre laser

Abstract: Very short erbium-fibre lasers with holographically written gratings in the erbium-doped fibre core are reported. An output power of 181 mu W was obtained from a 2cm long diode-pumped laser. A 1 cm long diode pumped laser had an output power of 57 mu W. As would be expected for such short cavity lengths, these lasers are robustly singlemode.< >

Optical fiber cabinet

Abstract: An optical fiber cabinet for enclosing various optical fiber connections and/or terminations. The optical fiber cabinet includes a frame which defines an optical fiber connection-termination area with the frame including a base having a bottom opening, vertical support members, and a removable upper frame member. Clam-shell doors are rotatably attached to the vertical support members of the frame and have a closed and open position. In the closed position, the clam-shell doors cooperate with the frame to enclose the optical fiber connection-termination area. In the open position, the clam-shell doors are disposed away from the optical fiber connection-termination area to allow both horizontal and vertical access to the optical fiber connection-termination area. A connection box within which the optical fiber connections are mounted is disposed within the optical fiber connection-termination area of the cabinet and includes a door rotatable between a closed and open position. The vertical support members of the cabinet are sized such that the connection box door is permitted to rotate substantially more than 90° between the closed and open positions when the clam-shell doors are in the open position.

Fiber optic array sensors, apparatus, and methods for concurrently visualizing and chemically detecting multiple analytes of interest in a fluid sample

Abstract: The present invention provides a unique fiber optic sensor which is able to provide a viewing zone for visual examination of a sample and its surrounding environment; and is able to conduct multiple assays concurrently using a plurality of different dyes immobilized at individual spatial positions within a dye sensing zone on the surface of the sensor. The present invention also provides apparatus for making precise optical determinations and measurements for multiple analytes of interest concurrently and provides methods of detection for multiple analytes of interest which can be correlated with specific parameters or other ligands for specific applications and purposes.

Soliton fiber ring laser

Abstract: A fiber ring laser that can produce nearly transform-limited soliton pulses is simulated. This laser has an erbium-doped optical-fiber amplifier and allows wavelength tuning through the interplay of fiber chromatic dispersion and the round-trip delay time of the laser. We show that a saturable absorber and a frequency limiter are required for the ring laser to self-start, i.e., to mode lock from initial noise and to operate stably. We also show that nonlinear polarization rotation with polarization selectivity inside the ring can act as a saturable absorber.

Reproducible Fabrication Technique of Nanometric Tip Diameter Fiber Probe for Photon Scanning Tunneling Microscope

Abstract: Nanometric tip diameter fiber probes for photon scanning tunneling microscopes (PSTM) were fabricated by selective chemical etching of GeO2-doped optical fibers. The cone angle θ of the fiber probe tip was controlled by varying the doping ratio of the fiber core and the composition of the etching solution, and the standard deviation of the cone angle Δθ was within 0.5°. A fiber probe with θ=20° and tip diameter of less than 10 nm was fabricated. This is, to the authors' knowledge, the sharpest PSTM probe which has ever been reported.

Reduced noise fiber optic towed array and method of using same

Abstract: A sensitive towed optical fiber sensor array 50, wherein the fiber sensors (60A-60N) are connected in parallel, and the optical fiber cable (34) is paid out from the towing ship at a velocity about equal to but opposite to the velocity of the towing ship. The fiber sensors (60A-60N) are immune to electromagnetic interference, and the output of the sensors can be isolated readily to the parallel hookup of the sensors. Turbulence and acceleration noise is greatly reduced due to the manner in which the fiber cable (34) is paid out, and crosstalk between sensors is eliminated.