Results for “Optical devices” — Page 31

NASA NTRS2007

Aligning Optical Fibers by Means of Actuated MEMS Wedges

Microelectromechanical systems (MEMS) of a proposed type would be designed and fabricated to effect lateral and vertical alignment of optical fibers with respect to optical, electro-optical, optoelectronic, and/or photonic devices on integrated circuit chips and similar monolithic device structures. A MEMS device of this type would consist of a pair of oppositely sloped alignment wedges attached to linear actuators that would translate the wedges in the plane of a substrate, causing an optical fiber in contact with the sloping wedge surfaces to undergo various displacements parallel and perpendicular to the plane. In making it possible to accurately align optical fibers individually during the packaging stages of fabrication of the affected devices, this MEMS device would also make it possible to relax tolerances in other stages of fabrication, thereby potentially reducing costs and increasing yields. In a typical system according to the proposal (see Figure 1), one or more pair(s) of alignment wedges would be positioned to create a V groove in which an optical fiber would rest. The fiber would be clamped at a suitable distance from the wedges to create a cantilever with a slight bend to push the free end of the fiber gently to the bottom of the V groove. The wedges would be translated in the substrate plane by amounts Dx1 and Dx2, respectively, which would be chosen to move the fiber parallel to the plane by a desired amount Dx and perpendicular to the plane by a desired amount Dy. The actuators used to translate the wedges could be variants of electrostatic or thermal actuators that are common in MEMS.

Morgan, Brian↗

NASA NTRS2017

Development and Testing of a Friction-Based Post-Installable Sensor for Subsea Fiber-Optic Monitoring Systems

This paper presents the design and development of a friction-based coupling device for a fiber-optic monitoring system that can be deployed on existing subsea structures. This paper provides a summary of the design concept, prototype development, prototype performance testing, and design refinements of the device. The results of the laboratory testing of the first prototype performed at the National Aeronautics and Space Administration (NASA) Johnson Space Center (JSC) are included in this paper. Limitations of the initial design were identified and future design improvements were proposed. These new features will enhance the coupling of the device and improve the monitoring system measurement capabilities. A major challenge of a post-installed instrumentation monitoring system is to ensure adequate coupling between the instruments and the structure of interest for reliable measurements. Friction-based coupling devices have the potential to overcome coupling limitations caused by marine growth and soil contamination on subsea structures, flowlines or risers. The work described in this paper investigates the design of a friction-based coupling device (friction clamp), which is applicable for pipelines and structures that are suspended in the water column and those that are resting on the seabed. The monitoring elements consist of fiber-optic sensors that are bonded to a metal clamshell with a high-friction coating. The friction clamp has a single hinge design to facilitate the operation of the clamp and dual rows of opposing fasteners to distribute the clamping force on the structure. The friction clamp can be installed by divers in shallow depths or by remotely operated vehicles in deep-water applications. NASA-JSC was involved in the selection and testing of the friction coating, and in the design and testing of the prototype clamp device. Four-inch diameter and eight-inch diameter sub-scale friction clamp prototypes were built and tested to evaluate the strain measuring capabilities of the design under different loading scenarios. The testing revealed some limitations of the initial design concept, and subsequent refinements were explored to improve the measurement performance of the system. This study was part of a collaboration between NASA-JSC and Astro Technology, Inc. within a study called Clear Gulf. The primary objective of the Clear Gulf study is to develop advanced instrumentation technologies that will improve operational safety and reduce the risk of hydrocarbon spillage. NASA provided unique insights, expansive test facilities, and technical expertise to advance these technologies that would benefit the environment, the public, and commercial industries.

Bentley, Nicole↗

NASA NTRS2017

Development and Testing of a Friction-Based Post-Installable Sensor for Subsea Fiber-Optic Monitoring System

This paper presents the design and development of a friction-based coupling device for a fiber-optic monitoring system that can be deployed on existing subsea structures. This paper provides a summary of the design concept, prototype development, prototype performance testing, and design refinements of the device. The results of the laboratory testing of the first prototype performed at the National Aeronautics and Space Administration (NASA) Johnson Space Center (JSC) are included in this paper. Limitations of the initial design were identified and future design improvements were proposed. These new features will enhance the coupling of the device and improve the monitoring system measurement capabilities. A major challenge of a post-installed instrumentation monitoring system is to ensure adequate coupling between the instruments and the structure of interest for reliable measurements. Friction-based coupling devices have the potential to overcome coupling limitations caused by marine growth and soil contamination on subsea structures, flowlines or risers. The work described in this paper investigates the design of a friction-based coupling device (friction clamp), which is applicable for pipelines and structures that are suspended in the water column and those that are resting on the seabed. The monitoring elements consist of fiber-optic sensors that are bonded to a metal clamshell with a high-friction coating. The friction clamp has a single hinge design to facilitate the operation of the clamp and dual rows of opposing fasteners to distribute the clamping force on the structure. The friction clamp can be installed by divers in shallow depths or by remotely operated vehicles in deep-water applications. NASA-JSC was involved in the selection and testing of the friction coating, and in the design and testing of the prototype clamp device. Four-inch diameter and eight-inch diameter sub-scale friction clamp prototypes were built and tested to evaluate the strain measuring capabilities of the design under different loading scenarios. The testing revealed some limitations of the initial design concept, and subsequent refinements were explored to improve the measurement performance of the system. This study was part of a collaboration between NASA-JSC and Astro Technology, Inc. within a study called Clear Gulf. The primary objective of the Clear Gulf study is to develop advanced instrumentation technologies that will improve operational safety and reduce the risk of hydrocarbon spillage. NASA provided unique insights, expansive test facilities, and technical expertise to advance these technologies that would benefit the environment, the public, and commercial industries.

Bentley, Nicole L.↗

NASA NTRS1989

Fiber optic links for microwave/millimeter-wave systems

Recent advances in device technology for microwave/mm-wave (M/MMW) analog fiber-optic communication systems are surveyed, with discussion of system parameters, design optimization methods, and hardware selection and manufacturing considerations. Particular attention is given to 1-km-link systems operating at 21, 30, and 12 GHz for satellite-communication, electronic-warfare, and radar applications. The design and fabrication simplicity of direct modulation is weighed against the wide bandwidth, low distortion, and mm-wave and frequency operation advantages of external modulation. Homodyne or heterodyne coherent detection is shown to improve system S/N by 10-20 dB over conventional detection methods. Diagrams, drawings, photographs, and graphs of typical performance data are included.

Pan, J. J.↗

NASA NTRS2002

Vacuum Arc Vapor Deposition Method and Apparatus for Applying Identification Symbols to Substrates

An apparatus for applying permanent markings onto products using a Vacuum Arc Vapor Deposition (VAVD) marker by accelerating atoms or molecules from a vaporization source onto a substrate to form human and/or machine-readable part identification marking that can be detected optically or via a sensing device like x-ray, thermal imaging, ultrasound, magneto-optic, micro-power impulse radar, capacitance, or other similar sensing means. The apparatus includes a housing with a nozzle having a marking end. A chamber having an electrode, a vacuum port and a charge is located within the housing. The charge is activated by the electrode in a vacuum environment and deposited onto a substrate at the marking end of the nozzle. The apparatus may be a hand-held device or be disconnected from the handle and mounted to a robot or fixed station.

Harry F Schramm↗

NASA NTRS1989

Optical joint transform correlation on the DMD

Initial experimental investigation of the deformable mirror device (DMD) in a joint optical transform correlation is reported. The inverted cloverleaf version of the DMD, in which form the DMD is phase-mostly but of limited phase range, is used. Binarized joint Fourier transforms were calculated for similar and dissimilar objects and written onto the DMD. Inverse Fourier transform was done in a diffraction order for which the DMD shows phase-mostly modulation. Matched test objects produced sharp correlation, distinct objects did not. Further studies are warranted and they are outlined.

Knopp, Jerome↗

NASA NTRS1992

Integrated device with diffractive polarization components for a magneto-optical disk head

The optical components in the detection train of a conventional magneto-optical (MO) disk head include a half-wave plate and a polarization beamsplitter. These polarization components are bulky and require specialized mounting hardware. In order to realize a more compact head, we propose that these elements be replaced by an integrated device composed of cascaded volume and surface-relief gratings. Herein, the proposed system is described in detail for the individual elements, theoretical and prototype element performance are compared, and the operational tolerances of these elements are discussed.

Haggans, Charles W.↗

NASA NTRS1984

Evaluation of a Magneto-optical Filter and a Fabry-perot Interferometer for the Measurement of Solar Velocity Fields from Space

A program was developed to evaluate the performance of three different devices as possible space-borne solar velocity field imagers. Two of these three devices, a magneto-optical filter and a molecular adherence Fabry-Perot interferometer were installed in a newly-constructed observing system located at the 60-foot tower telescope at the Mt. Wilson Observatory. Time series of solar filtergrams and Dopplergrams lasting up to 10 hours per day were obtained with the filter while shorter runs were obtained with the Fabry-Perot. Two-dimensional k (sub h)-omega power spectra which show clearly the well-known p-mode ridges were computed from the time series obtained with the magneto-optical filter. These power spectra were compared with similar power spectra obtained recently with the 13.7-m McMath spectrograph at Kitt Peak.

Rhodes, E. J., Jr.↗

NASA NTRS1980

A dual charge-coupled device /CCD/, astronomical spectrometer and direct imaging camera. I - Optical and detector systems

The MASCOT (MIT Astronomical Spectrometer/Camera for Optical Telescopes), an instrument capable of simultaneously performing both direct imaging and spectrometry of faint objects, is examined. An optical layout is given of the instrument which uses two CCD's mounted on the same temperature regulated detector block. Two sources of noise on the signal are discussed: (1) the CCD readout noise, which results in a constant uncertainty in the number of electrons collected from each pixel; and (2) the photon counting noise. The sensitivity of the device is limited by the sky brightness, the overall quantum efficiency, the resolution, and the readout noise of the CCD. Therefore, total system efficiency is calculated at about 15%.

Meyer, S. S.↗

NASA NTRS2007

Raman-Suppressing Coupling for Optical Parametric Oscillator

A Raman-scattering-suppressing input/ output coupling scheme has been devised for a whispering-gallery-mode optical resonator that is used as a four-wave-mixing device to effect an all-optical parametric oscillator. Raman scattering is undesired in such a device because (1) it is a nonlinear process that competes with the desired nonlinear four-wave conversion process involved in optical parametric oscillation and (2) as such, it reduces the power of the desired oscillation and contributes to output noise. The essence of the present input/output coupling scheme is to reduce output loading of the desired resonator modes while increasing output loading of the undesired ones.

Savchenkov, Anatoliy↗

NASA NTRS1975

Study of hollow corner retroreflectors for use in a synchronous orbit

The performance of a hollow corner cube retroreflector made up of three mutually perpendicular optically flat mirrors when undergoing the thermal-mechanical strains induced by a spacecraft environment was studied. Of particular interest was a device of 200 square centimeter optical aperture used on a satellite in a synchronous orbit. It was assumed that the reflector always faces the earth. The effects of direct solar irradiance, earthshine, and albedo were considered. The results included the maximum mirror surface temperature during the orbit as well as the worst-case loss of optical performance due to thermally-induced mirror distortions. It was concluded that a device made of three suitably coated flat ULE mirrors, optically contacted to each other and supported mechanically in a nonrigid mount, would be expected to concentrate over 80 percent of the theoretical maximum energy in the central of the far field diffraction pattern. Continued development of the device through a detailed design, fabrication, and test phase was recommended.

Yoder, P. R., Jr.↗

NASA NTRS1992

High-speed electro-optic switch with -80 dB crosstalk

Special device modeling, design and layout, and precision processing controls were employed to fabricate new balanced-bridge 2x2 and 4x4 switches on X-cut, Y-propagation LiNbO3 substrate using Ti indiffused optical waveguides. The best of these devices achieved extinction ratio and crosstalk isolation of better than 93 dB electrically (46.5 dB optically). The new switches demonstrate good reproducibility with electrical crosstalk less than -80 dB.

Pan, J. J.↗

NASA NTRS2016

Magneto-Optic Field Coupling in Optical Fiber Bragg Gratings

The invention is a magneto-optic coupled magnetic sensor that comprises a standard optical fiber Bragg grating system. The system includes an optical fiber with at least one Bragg grating therein. The optical fiber has at least an inner core and a cladding that surrounds the inner core. The optical fiber is part of an optical system that includes an interrogation device that provides a light wave through the optical fiber and a system to determine the change in the index of refraction of the optical fiber. The cladding of the optical fiber comprises at least a portion of which is made up of ferromagnetic particles so that the ferromagnetic particles are subject to the light wave provided by the interrogation system. When a magnetic field is present, the ferromagnetic particles change the optical properties of the sensor directly.

Carman, Gregory P.↗

NASA NTRS1988

Magnetic and electric field meters developed for the US Department of Energy

This report describes work done at the Jet Propulsion Laboratory for the Office of Energy Storage and Distribution of DOE on the measurement of power line fields. A magnetic field meter is discussed that uses fiber optics to couple a small measuring probe to a remote readout device. The use of fiber optics minimizes electric field perturbation due to the presence of the probe and provides electric isolation for the probe, so that it could be used in a high field or high voltage environment. Power to operate the sensor electronics is transferred via an optical fiber, and converted to electrical form by a small photodiode array. The fundamental, the second and third harmonics of the field are filtered and separately measured, as well as the broadband rms level of the field. The design of the meter is described in detail and data from laboratory tests are presented. The report also describes work done to improve the performance of a DC bushing in a Swedish factory, using the improved meter. The DC electric fields are measured with synchronous detection to provide field magnitude data in two component directions.

Kirkham, H.↗

NASA NTRS1991

Use of rotating pinholes and reticles for calibration of cloud droplet instrumentation

Calibration devices for the Forward Scattering Spectrometer Probe (FSSP) and the Optical Array Probe (OAP) were developed. The device used with the FSSP is a rotating pinhole calibrator. It utilizes light diffracted by a pinhole of a known diameter to simulate scattered light from a water droplet. This device can be used to calibrate the FSSP, measure the FSSP's optical collection angles and for instrument alignment and troubleshooting. The device used with the OAP is a rotating reticle calibrator. Chrome disks of a known diameter on the reticle are used for calibration of the OAP and for determining the OAP's response to out-of-focus particles in the probe volume.

Hovenac, Edward A.↗

NASA NTRS1991

All-optical photochromic spatial light modulators based on photoinduced electron transfer in rigid matrices

A single material (not a multi-element structure) spatial light modulator may be written to, as well as read out from, using light. The device has tailorable rise and hold times dependent on the composition and concentration of the molecular species used as the active components. The spatial resolution of this device is limited only by light diffraction as in volume holograms. The device may function as a two-dimensional mask (transmission or reflection) or as a three-dimensional volume holographic medium. This device, based on optically-induced electron transfer, is able to perform incoherent to coherent image conversion or wavelength conversion over a wide spectral range (ultraviolet, visible, or near-infrared regions).

Beratan, David N.↗

NASA NTRS1981

Short-range self-pulsed optical radar

Laser for radar device is retriggered when previous laser pulse is reflected from target. Target range R is computed from number of pulses triggered per time interval. Radar accurately measures distances up to 500 meters; it is useful for determining surface shape of relfectors in large, high-gain, highly directional antennas and for other short-range surveying.

Berdahl, C. M.↗

NASA NTRS1991

Optical flow versus retinal flow as sources of information for flight guidance

The appropriate description is considered of visual information for flight guidance, optical flow vs. retinal flow. Most descriptions in the psychological literature are based on the optical flow. However, human eyes move and this movement complicates the issues at stake, particularly when movement of the observer is involved. The question addressed is whether an observer, whose eyes register only retinal flow, use information in optical flow. It is suggested that the observer cannot and does not reconstruct the image in optical flow; instead they use retinal flow. Retinal array is defined as the projections of a three space onto a point and beyond to a movable, nearly hemispheric sensing device, like the retina. Optical array is defined as the projection of a three space environment to a point within that space. And flow is defined as global motion as a field of vectors, best placed on a spherical projection surface. Specifically, flow is the mapping of the field of changes in position of corresponding points on objects in three space onto a point, where that point has moved in position.

Cutting, James E.↗