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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 307 records · Page 17

All sources NASA NTRS DOE OSTI

NASA NTRS1993

Fiber optic and laser sensors X; Proceedings of the Meeting, Boston, MA, Sept. 8-11, 1992

Topics addressed include acoustic and pressure sensors; fiber optic gyros; electric and magnetic field sensors; bend, strain, and temperature sensors; industrial applications of sensors; and processing techniques. Particular attention is given to fiber optic interferometric acoustic sensors for wind tunnel applications, polished coupler and resonator fabrication, second-harmonic detection for rotation sensing in fiber optic gyros, simplified control theory in closed-loop fiber optic gyroscopes, and a Fabry-Perot sensor with digital signal processing for the measurement of magnetostriction. Also discussed are a Bragg fiber laser sensor, commercialization of fiber optic strain gauge systems, thermal ignition in hazardous environments due to stray light from optical fibers, a system for absolute measurements by interferometric sensors, and high-performance interferometric demodulation techniques.

Udd, Eric↗

NASA NTRS1991

Optical and mechanical response of high temperature optical fiber sensors

The National Aerospace Plane (NASP) will experience temperatures as high as 2500 F at critical locations in its structure. Optical fiber sensors were proposed as a means of monitoring the temperature in these critical regions by either bonding the optical fiber to, or embedding the optical fiber in, metal matrix composite (MMC) components. Unfortunately, the anticipated NASP temperature ranges exceed the glass transition region of the optical fiber glass. The attempt is made to define the operating temperature range of optical fiber sensors from both optical and mechanical perspectives. A full non-linear optical analysis was performed by modeling the optical response of an isolated sensor cyclically driven through the glass transition region.

Sirkis, Jim↗

DOE OSTI2024

Assessing the Expansion of Ground-Motion Sensing Capability in Smart Cities via Internet Fiber-Optic Infrastructure

Monitoring ground motion in smart cities can improve the public safety by providing critical insights on natural and anthropogenic hazards, for example, earthquakes, landslides, explosions, infrastructure failures, and so forth. Although seismic activity is typically measured using dedicated point sensors (e.g., geophones and accelerometers), techniques such as distributed acoustic sensing have demonstrated the utility of using fiber-optic cable to detect seismic activity over comparable distances. In this article, we present the results of a study that quantifies the expansion in an area monitored for low-amplitude ground-motion events by augmenting existing point sensors with the internet fiber-optic cable infrastructure. Here we begin by describing our methodology, which utilizes geospatial data on point sensors and internet optical fiber deployed in metropolitan statistical areas (MSAs) in the United States. We extend these data to identify the area that can be monitored by (1) considering the observed seismic noise data in target locations, (2) applying the model from Wilson et al. (2021) to understand the potential coverage area gains using optical fiber sensing, and (3) optimizing the selection of fiber segments to maximize coverage and minimize deployment costs. We implement our methodology in ArcGIS to assess the additional area that can be monitored for low-amplitude ground-motion events (i.e., magnitude >0.5) by utilizing internet fiber-optic cables in the 100 most populous MSAs in the United States. We find that the addition of internet fiber-based sensors in MSAs would increase the area monitored on average by over an order of magnitude from 1% to 12%, if the subset of fiber cable segments that maximize coverage and minimize deployment costs is chosen even if only 20% of all fibers are used.

58 GEOSCIENCES↗

NASA NTRS1976

Bit error rate measurement for evaluation of a fiber optic link

Digital fiber-optic data-link terminal modules are being developed in a number of laboratories, and often the modules take the form of black boxes without convenient access to internal signals. This paper discusses types of measurements which can be made using only the digital terminals of the link. Bit-error-rate (BER) vs signal-power data can, of course, provide a means for proving overall link performance, but it can also be used to determine certain internal parameters of the receiver. The theoretical dependence of the BER-vs-light-signal-power curve shape on receiver input-noise equivalent power and comparator slicing level is discussed. BER-vs-light-signal-power measurements obtained with an experimental link are presented and interpreted with the aid of the theoretical curves. The effects of other problems, such as hum or oscillation, on the BER data are mentioned. Sensitivity of the system BER to bit rate is also discussed, with application to determining system operating limits. Since BER measurements are simple to make and can easily be automated, they may prove to be a useful means for either laboratory evaluation or production-line acceptance testing of sealed terminal modules.

Bergman, L. A.↗

NASA NTRS1984

Distributed strain measurement in a rectangular plate using an array of optical fiber sensors

Single mode optical fiber waveguide has been used to determine the two-dimensional strain distribution on a simply supported rectangular plate. Each of the fifty individual fibers in the rectangular grid array attached to one surface of the plate yields a measurement of the strain integrated along the length of that fiber on the specimen. By using similar sensor information from all of the fibers, both the functional form and the amplitude of the distribution may be determined. Limits on the dynamic range and spatial resolution are indicated. Applications in the measurement of internal strain and the monitoring of physically small critical-structural components are suggested.

Claus, R. O.↗

NASA NTRS1984

Stress concentration measurement in a rectangular plate using an array of embedded optical fibers

Embedded single mode optical fiber waveguide has been used to determine the two-dimensional stress distribution produced by point loading on a simply supported rectangular plate. Each of the fifty individual fibers in the rectangular grid array attached to the plate yields a measurement of the stress integrated along the length of that fiber on the specimen. By using information from all the fibers, both the functional form and the amplitude of the distribution may be determined. Limits on the dynamic range and spatial resolution are indicated. Applications in the measurement of internal stress and the monitoring of physically small critical structural components are suggested.

Claus, R. O.↗

NASA NTRS1986

Wide-area remote-sensing system of pollution and gas dispersal by near-infrared absorption based on low-loss optical fiber network

An all optical remote sensing system utilizing long distance, ultralow loss optical fiber networks is studied and discussed for near infrared absorption measurements of combustible and/or explosive gases such as CH4 and C3H8 in our environment, including experimental results achieved in a diameter more than 20 km. The use of a near infrared wavelength range is emphasized.

Inaba, H.↗

NASA NTRS1991

Fiber optic sensing system

A fiber optic interferometer utilizes a low coherence light emitting diode (LED) laser as a light source which is filtered and driven at two RF frequencies, high and low, that are specific to the initial length of the resonator chamber. A displacement of a reflecting mirror changes the length traveled by the nonreferencing signal. The low frequency light undergoes destructive interference which reduces the average intensity of the wave while the high frequency light undergoes constructive interference which increases the average intensity of the wave. The ratio of these two intensity measurements is proportional to the displacement incurred.

Adamovsky, Grigory↗

NASA NTRS1993

Machine Tests Optical Fibers In Flexure

Machine repeatedly flexes single optical fiber or cable or bundle of optical fibers at low temperature. Liquid nitrogen surrounds specimen as it is bent back and forth by motion of piston. Machine inexpensive to build and operate. Tests under repeatable conditions so candidate fibers, cables, and bundles evaluated for general robustness before subjected to expensive shock and vibration tests.

Darejeh, Hadi↗

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.↗

NASA NTRS1990

Fiber optic sensors IV; Proceedings of the Third European Congress on Optics, The Hague, Netherlands, Mar. 13, 14, 1990

Recent advances in fiber-optic sensor (FOS) technology are examined in reviews and reports. Sections are devoted to components for FOSs, special fibers for FOSs, interferometry, FOS applications, and sensing principles and influence. Particular attention is given to solder glass sealing technology for FOS packaging, the design of optical-fiber current sensors, pressure and temperature effects on beat length in highly birefringent optical fibers, a pressure FOS based on vibrating-quartz-crystal technology, remote sensing of flammable gases using a fluoride-fiber evanescent probe, a displacement sensor with electronically scanned white-light interferometer, the use of multimode laser diodes in low-coherence coupled-cavity interferometry, electronic speckle interferometry compensated for environmentally induced phase noise, a dual-resolution noncontact vibration and displacement sensor based on a two-wavelength source, and fiber optics in composite materials.

Kersten, Ralf T.↗

NASA NTRS2000

On-Board Fiber-Optic Network Architectures for Radar and Avionics Signal Distribution

Continued progress in both civil and military avionics applications is overstressing the capabilities of existing radio-frequency (RF) communication networks based on coaxial cables on board modem aircrafts. Future avionics systems will require high-bandwidth on- board communication links that are lightweight, immune to electromagnetic interference, and highly reliable. Fiber optic communication technology can meet all these challenges in a cost-effective manner. Recently, digital fiber-optic communication systems, where a fiber-optic network acts like a local area network (LAN) for digital data communications, have become a topic of extensive research and development. Although a fiber-optic system can be designed to transport radio-frequency (RF) signals, the digital fiber-optic systems under development today are not capable of transporting microwave and millimeter-wave RF signals used in radar and avionics systems on board an aircraft. Recent advances in fiber optic technology, especially wavelength division multiplexing (WDM), has opened a number of possibilities for designing on-board fiber optic networks, including all-optical networks for radar and avionics RF signal distribution. In this paper, we investigate a number of different novel approaches for fiber-optic transmission of on-board VHF and UHF RF signals using commercial off-the-shelf (COTS) components. The relative merits and demerits of each architecture are discussed, and the suitability of each architecture for particular applications is pointed out. All-optical approaches show better performance than other traditional approaches in terms of signal-to-noise ratio, power consumption, and weight requirements.

Alam, Mohammad F.↗

NASA NTRS1997

Fiber Optic Experience with the Smart Actuation System on the F-18 Systems Research Aircraft

High bandwidth, immunity to electromagnetic interference, and potential weight savings have led to the development of fiber optic technology for future aerospace vehicle systems. This technology has been incorporated in a new smart actuator as the primary communication interface. The use of fiber optics simplified system integration and significantly reduced wire count. Flight test results showed that fiber optics could be used in aircraft systems and identified critical areas of development of fly-by-light technology. This paper documents the fiber optic experience gained as a result of this program, and identifies general design considerations that could be used in a variety of specific applications of fiber optic technology. Environmental sensitivities of fiber optic system components that significantly contribute to optical power variation are discussed. Although a calibration procedure successfully minimized the effect of fiber optic sensitivities, more standardized calibration methods are needed to ensure system operation and reliability in future aerospace vehicle systems.

Zavala, Eddie↗

NASA NTRS1992

Optical fiber spectroscopy: A study of the luminescent properties of the europium ion for thermal sensors

Recently, there has been interest in developing a distributed temperature sensor integrated into an optical fiber. Such a system would allow embedding of the optical fiber within or on a structural material to provide for continuous monitoring of the material's temperature. Work has already begun on the development of a temperature sensor using the temperature dependent emission spectra from the lanthanide rare earths doped into crystalline hosts. The lifetime, the linewidth and the integrated intensity of this emission are each sensitive to changes in the temperature and can provide a basis for thermometry. One concept for incorporating this phenomena into an optical fiber based sensor involves bonding the optically active material to the cladding of an optical fiber and allowing the luminescent light to couple into the the fiber by the evanescent wave. Experimental work developing this concept has already been reported. Measurements of the linewidth of Eu3+:Y2O3, diffused into a fiber, made by Albin clearly show a strong and regular dependence on temperature over the range of 300 to 1000 K. We report here on a study of the temperature dependence of the lineshape of the emission at 611 nm using the data in references. We focus attention on understanding the general behavior of the Eu3+:Y2O3 system. Building upon understanding of this system we will be able to establish the physical criterial for a good optical fiber based temperature sensor and then to examine available data on other lanthanide rare earths and transition metal ions to determine the best luminescent system for temperature sensing in an optical fiber.

Buoncristiani, A. Martin↗

DOE OSTI2026

Exploring the Feasibility of Modern Fiber Optics in Offshore Mooring Condition Monitoring

This project explored the feasibility of using fiber-optic sensing technologies for condition monitoring of offshore synthetic mooring lines used in marine renewable energy systems. The work focused on evaluating optical fiber materials, interrogation methods, and rope-embedment approaches capable of enabling distributed strain or elongation measurements along mooring lines.

16 TIDAL AND WAVE POWER↗

NASA NTRS1978

Fresnel drag effect in fiber optic gyroscope

Consideration is given to the development of a low-noise fiber-optic ring interferometer gyroscope. A technique for measuring the Fresnel drag coefficient of optical fibers is described, and the accuracy of the technique is considered. An experiment is performed which allows verification of the Einstein velocity addition theorem to the first nonlinear term. An experimental setup for measuring Fresnel drag is described: it consists of a Sagnac interferometer and a Fresnel drag measurement configuration.

Vali, V.↗

NASA NTRS1988

Optical fiber methods for the NDE of smart skins and structures

The recent use of optical fiber waveguides as sensors in and on materials and structures is briefly reviewed. Recent progress in the application of fiber optic sensors for composite cure monitoring, in-service static and dynamic materials evaluation, and material degradation determination are outlined. The integration of sensors, actuators, and control system electronics for achieving active material and structural response is described.

Claus, R. O.↗

NASA NTRS2001

Demodulation System for Fiber Optic Bragg Grating Dynamic Pressure Sensing

Fiber optic Bragg gratings have been used for years to measure quasi-static phenomena. In aircraft engine applications there is a need to measure dynamic signals such as variable pressures. In order to monitor these pressures a detection system with broad dynamic range is needed. This paper describes an interferometric demodulator that was developed and optimized for this particular application. The signal to noise ratio was maximized through temporal coherence analysis. The demodulator was incorporated in a laboratory system that simulates conditions to be measured. Several pressure sensor configurations incorporating a fiber optic Bragg grating were also explored. The results of the experiments are reported in this paper.

Lekki, John D.↗