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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS2008

Data Optical Networking Architecture Using Wavelength-Division Multiplexing Method for Optical Sensors

Recently there has been a growth in the number of fiber optical sensors used for health monitoring in the hostile environment of commercial aircraft. Health monitoring to detect the onset of failure in structural systems from such causes as corrosion, stress corrosion cracking, and fatigue is a critical factor in safety as well in aircraft maintenance costs. This report presents an assessment of an analysis model of optical data networking architectures used for monitoring data signals among these optical sensors. Our model is focused on the design concept of the wavelength-division multiplexing (WDM) method since most of the optical sensors deployed in the aircraft for health monitoring typically operate in a wide spectrum of optical wavelengths from 710 to 1550 nm.

Nguyen, Hung D.↗
NASA NTRS1991

Integrated optics for fiber optic sensors

Recent progress achieved in the field of fiber-optic sensor applications is discussed with emphasis placed on LiNbO3-based integrated optics (IO). Particular consideration is given to advanced electromagnetic-field sensors, an integrated laser vibrometer system, and a fiber-optic gyroscope system. It is shown that the multifunction IO chips have enabled high perforamance fiber-optic sensors (e.g., fiber-optic gyros), provided advanced and unique signal processing capabilities and advanced architectures, and have a potential of making fiber-optic sensors at low cost.

Minford, W. J.↗
NASA NTRS1987

Overview of Fiber-Optical Sensors

Design, development, and sensitivity of sensors using fiber optics reviewed. State-of-the-art and probable future developments of sensors using fiber optics described in report including references to work in field. Serves to update previously published surveys. Systems incorporating fiber-optic sensors used in medical diagnosis, navigation, robotics, sonar, power industry, and industrial controls.

Depaula, Ramon P.↗
DOE OSTI2024

Systems and methods for optical sensor protection

The present disclosure relates to an optical sensor protection system. The system may have a sensor for receiving an incoming optical signal, a passive sensing and modulation component, and an active sensing and modulation subsystem. The passive sensing and modulation component is configured to sense when a first characteristic is associated with the incoming optical signal is present that adversely affects operation of the sensor, and redirects at least a portion of the incoming optical signal thereof away from the sensor to thus reduce an intensity of the incoming optical signal reaching the sensor. The sensor is located on an image plane downstream of the ISM subsystem, relative to a path of travel of the incoming optical signal. The active sensing and modulation subsystem has an active modulation component and is located upstream of the passive sensing and modulation component, relative to the path of travel of the incoming optical signal, and is also located on a conjugate image plane, and is configured to use the redirected portion of the incoming optical signal as feedback in controlling a modification of the incoming optical signal to reduce a risk of damage to the passive sensing and modulation component.

Panas, Robert Matthew↗
NASA NTRS2014

Lightning Current Measurement with Fiber-Optic Sensor

A fiber-optic current sensor is successfully developed with many potential applications for electric current measurement. Originally developed for in-flight lightning measurement, the sensor utilizes Faraday Effect in an optical fiber. The Faraday Effect causes linear light polarization in a fiber to rotate when the fiber is exposed to a magnetic field. The polarization change is detected using a reflective polarimetric scheme. Forming fiber loops and applying Ampere's law, measuring the total light rotation results in the determination of the total current enclosed. The sensor is conformable to complex structure geometry. It is also non-conductive and immune to electromagnetic interference, saturation or hysteresis. Installation is non-intrusive, and the sensor can be safely routed through flammable areas. Two similar sensor systems are described in this paper. The first system operates at 1310nm laser wavelength and is capable of measuring approximately 300 A - 300 kA, a 60 dB range. Laboratory validation results of aircraft lighting direct and in-direct effect current amplitudes are reported for this sensor. The second system operates at 1550nm wavelength and can measure about 400 A - 400 kA. Triggered-lightning measurement data are presented for this system. Good results are achieved in all cases.

Nguyen, Truong X.↗
DOE OSTI2023

Integrating fiber optic sensors into metallic components for sensing in harsh environments

The integration of fiber optic sensors into high-temperature materials is critical for real-time monitoring and autonomous operation of engineering systems. This study demonstrated a spark plasma sintering (SPS)-assisted embedding process for integrating sapphire fiber optic sensors into stainless steel components during part fabrication. Optical fibers were encapsulated in stainless steel 316L powders which were sintered at different fabrication conditions using SPS to investigate the effects of sintering parameters on the embedment. Measurements of optical transmittance, combined with microstructural analysis (X-ray computed tomography and scanning electron microscopy) and mechanical testing (tensile and microhardness), were conducted to examine the fiber functionality, fiber–matrix bonding quality, and properties of the sintered materials. Here, the results show that under suitable fabrication conditions, intact optical fibers can be encapsulated in highly-densified (>98 % relative density) stainless steel components. These conditions also led to a good bond at the fiber–matrix interface with micron-sized material interdiffusion across the interface. The sintering parameters were observed to affect fiber optical attenuation, where high temperature, pressure, and hold time during SPS enhanced fiber–matrix bonding and adversely affected optical transmission. Tensile testing confirmed the superior tensile strength and ductility of the matrix fabricated by SPS. Furthermore, the materials exhibited limited strength reduction (~70 MPa) upon the integration of fibers. This study demonstrates the effectiveness of SPS for fiber-material integration for high-temperature applications.

36 MATERIALS SCIENCE↗
NASA NTRS1998

Optical Sensors based on single arm thin film Waveguide Interferometer

The second achievement meets the second objective for the second year. We choose adjustable prism couplers for connecting the sensor to optical fiber lines in our design of a breadboard prototype of the sensor. These couplers have good coupling efficiency at relatively low cost comparing to any other alternatives such as grating couplers. The third accomplishment meets the third objective for the second year. We performed testing the breadboard prototype of the sensor using heating as a technique of changing its refractive index. The only difference is that we ruled out the channel waveguides as irrelevant to the final goals of the project. The feasibility of the sensor can be shown for the slab waveguide configuration without usage of relatively expensive technologies of channel waveguide delineation.

Sarkisov, Sergey S.↗
NASA NTRS1989

Strain and dynamic measurements using fiber optic sensors embedded into graphite/epoxy tubes

Graphite/epoxy tubes were fabricated with embedded optical fibers to evaluate the feasibility of monitoring strains with a fiber optic technique. Resistance strain gauges were attached to the tubes to measure strain at four locations along the tube for comparison with the fiber optic sensors. Both static and dynamic strain measurements were made with excellent agreement between the embedded fiber optic strain sensor and the strain gauges. Strain measurements of 10(exp -7) can be detected with the optical phase locked loop (OPLL) system using optical fiber. Because of their light weight, compatibility with composites, immunity to electromagnetic interference, and based on the static and dynamic results obtained, fiber optic sensors embedded in composites may be useful as the sensing component of smart structures.

Dehart, D. W.↗
DOE OSTI2024

Embedded Fiber Optic Sensors in Structural Materials for Sensing in Extreme Environments

This slide deck presents the research results in embedding fiber optic sensors in structural materials. Fiber optic sensors were embedded in stainless steel and nickel via electric field assisted sintering. The embedded sensors were evaluated in terms of fiber integrity, fiber-matrix bonding, fiber functionality, mechanical properties, and machinability.

36 - MATERIALS SCIENCE↗
NASA NTRS1995

The 1994 Fiber Optic Sensors for Aerospace Technology (FOSAT) Workshop

The NASA Lewis Research Center conducted a workshop on fiber optic technology on October 18-20, 1994. The workshop objective was to discuss the future direction of fiber optics and optical sensor research, especially in the aerospace arena. The workshop was separated into four sections: (1) a Systems Section which dealt specifically with top level overall architectures for the aircraft and engine; (2) a Subsystems Section considered the parts and pieces that made up the subsystems of the overall systems; (3) a Sensor/Actuators section considered the status of research on passive optical sensors and optical powered actuators; and (4) Components Section which addressed the interconnects for the optical systems (e.g., optical connectors, optical fibers, etc.). This report contains the minutes of the discussion on the workshop, both in each section and in the plenary sessions. The slides used by a limited number of presenters are also included as presented. No attempt was made to homogenize this report. The view of most of the attendees was: (1) the government must do a better job of disseminating technical information in a more timely fashion; (2) enough work has been done on the components, and system level architecture definition must dictate what work should be done on components; (3) a Photonics Steering Committee should be formed to coordinate the efforts of government and industry in the photonics area, to make sure that programs complimented each other and that technology transferred from one program was used in other programs to the best advantage of the government and industry.

Baumbick, Robert↗
NASA NTRS1992

Active vibration control using a modal-domain fiber optic sensor

A closed-loop control experiment is described in which vibrations of a cantilevered beam are suppressed using measurements from a modal-domain fiber optic sensor. Modal-domain sensors are interference between the modes of a few-mode optical waveguide to detect strain. The fiber is bonded along the length of the beam and provides a measurement related to the strain distribution on the surface of the beam. A model for the fiber optic sensor is derived, and this model is integrated with the dynamic model of the beam. A piezoelectric actuator is also bonded to the beam and used to provide control forces. Control forces are obtained through dynamic compensation of the signal from the fiber optic sensor. The compensator is implemented with a real-time digital controller. Analytical models are verified by comparing simulations to experimental results for both open-loop and closed-loop configurations.

Cox, David E.↗
NASA NTRS1990

Architecture for fiber-optic sensors and actuators in aircraft propulsion systems

This paper describes a design for fiber-optic sensing and control in advanced aircraft Electronic Engine Control (EEC). The recommended architecture is an on-engine EEC which contains electro-optic interface circuits for fiber-optic sensors. Size and weight are reduced by multiplexing arrays of functionally similar sensors on a pairs of optical fibers to common electro-optical interfaces. The architecture contains interfaces to seven sensor groups. Nine distinct fiber-optic sensor types were found to provide the sensing functions. Analysis revealed no strong discriminator (except reliability of laser diodes and remote electronics) on which to base a selection of preferred common interface type. A hardware test program is recommended to assess the relative maturity of the technologies and to determine real performance in the engine environment.

Glomb, W. L., Jr.↗
NASA NTRS2001

Shaft Position Optical Sensor

The present invention is an optical sensor that senses the movement of a shaft. Detection of radial movement is made when a portion of light incident on the shaft sensor-target is blocked. For detection of axial movement, a disk with flat surface is mounted and used to block a portion of light. The variation in the amount of light allowed to pass through is a measure of the position of the shaft. As proposed by this invention, significant improvement is made with respect to sensitivity and linearity of the system when the light is permanently partially blocked. To accomplish this goal this invention adds a boss to the system. To eliminate possible drift of system performance due to LED degradation or temperature variation, a feedback feature is added to the system.

Kenneth A Blumenstock↗
NASA NTRS1990

The Design of Optical Sensor for the Pinhole/Occulter Facility

Three optical sight sensor systems were designed, built and tested. Two optical lines of sight sensor system are capable of measuring the absolute pointing angle to the sun. The system is for use with the Pinhole/Occulter Facility (P/OF), a solar hard x ray experiment to be flown from Space Shuttle or Space Station. The sensor consists of a pinhole camera with two pairs of perpendicularly mounted linear photodiode arrays to detect the intensity distribution of the solar image produced by the pinhole, track and hold circuitry for data reduction, an analog to digital converter, and a microcomputer. The deflection of the image center is calculated from these data using an approximation for the solar image. A second system consists of a pinhole camera with a pair of perpendicularly mounted linear photodiode arrays, amplification circuitry, threshold detection circuitry, and a microcomputer board. The deflection of the image is calculated by knowing the position of each pixel of the photodiode array and merely counting the pixel numbers until threshold is surpassed. A third optical sensor system is capable of measuring the internal vibration of the P/OF between the mask and base. The system consists of a white light source, a mirror and a pair of perpendicularly mounted linear photodiode arrays to detect the intensity distribution of the solar image produced by the mirror, amplification circuitry, threshold detection circuitry, and a microcomputer board. The deflection of the image and hence the vibration of the structure is calculated by knowing the position of each pixel of the photodiode array and merely counting the pixel numbers until threshold is surpassed.

Greene, Michael E.↗
NASA NTRS1983

Optical Sensor for Robotics

Optical Method for precisely docking spacecraft and satellite promises useful in terrestrial applications, such as control of robot movements in manufacturing. Reflections of laser beam from patterns on satellite yield information on radial misalinement, angle between axes, and range. Target pattern consists of rings of alternating high and low reflectivity and central section where reflectivity varies with angle of incidence but not with position.

Weindling, F.↗
DOE OSTI2024

Distributed Temperature Profiles of Silicon Carbide Catalyst Bed in a Microwave Reactor using Fiber-optic Sensor

Microwave heating is of great interest for reducing greenhouse gas emissions of catalytic chemical conversion processes because it can heat up the reactants rapidly and efficiently and accelerate reaction rates. In microwave-assisted catalytic thermochemical conversion processes, accurate internal temperature measurement would help facilitate effective process control. Metallic thermocouples interfere and spark in the microwave heating environment, so they are not an option. Infrared pyrometers typically provide a single temperature value by averaging over a finite surface area of the catalyst bed. In this work, we use fiber-optic sensors passing through the catalyst bed to provide more accurate temperatures along the height of the catalyst bed. The fiber optic sensors are immune to the electromagnetic microwave radiation and provide temperature profiles along their length. Here, custom fiber-optic sensors were coupled to the optical distributed temperature sensing devices to measure the temperature profiles along the height of the catalyst bed at high temperatures with ~1 mm spatial resolution. The sensing devices use optical frequency domain reflectometry (OFDR) technique for distributed temperature measurement. This work shows the temperature profiles along the height of the silicon carbide powder catalyst bed in the variable and fixed frequency microwave reactors.

Thapa, Juddha↗