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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 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS1995

Calculated coupling efficiency between an elliptical-core optical fiber and an optical waveguide over temperature

To determine the feasibility of coupling the output of a single-mode optical fiber into a single-mode rib waveguide in a temperature varying environment, a theoretical calculation of the coupling efficiency between the two was investigated. Due to the complex geometry of the rib guide, there is no analytical solution to the wave equation for the guided modes, thus, approximation and/or numerical techniques must be utilized to determine the field patterns of the guide. In this study, three solution methods were used for both the fiber and guide fields; the effective-index method (EIM), Marcatili's approximation, and a Fourier method. These methods were utilized independently to calculate the electric field profile of each component at two temperatures, 20 C and 300 C, representing a nominal and high temperature. Using the electric field profile calculated from each method, the theoretical coupling efficiency between an elliptical-core optical fiber and a rib waveguide was calculated using the overlap integral and the results were compared. It was determined that a high coupling efficiency can be achieved when the two components are aligned. The coupling efficiency was more sensitive to alignment offsets in the y direction than the x, due to the elliptical modal field profile of both components. Changes in the coupling efficiency over temperature were found to be minimal.

Tuma, Margaret L.↗
NASA NTRS2012

Application of Fiber Optic Instrumentation

Fiber optic sensing technology has emerged in recent years offering tremendous advantages over conventional aircraft instrumentation systems. The advantages of fiber optic sensors over their conventional counterparts are well established; they are lighter, smaller, and can provide enormous numbers of measurements at a fraction of the total sensor weight. After a brief overview of conventional and fiber-optic sensing technology, this paper presents an overview of the research that has been conducted at NASA Dryden Flight Research Center in recent years to advance this promising new technology. Research and development areas include system and algorithm development, sensor characterization and attachment, and real-time experimentally-derived parameter monitoring for ground- and flight-based applications. The vision of fiber optic smart structure technology is presented and its potential benefits to aerospace vehicles throughout the lifecycle, from preliminary design to final retirement, are presented.

Richards, William Lance↗
NASA NTRS1986

US long distance fiber optic networks: Technology, evolution and advanced concepts. Volume 2: Fiber optic technology and long distance networks

The study projects until 2000 the evolution of long distance fiber optic networks in the U.S. Volume 1 is the Executive Summary. Volume 2 focuses on fiber optic components and systems that are directly related to the operation of long-haul networks. Optimistic, pessimistic and most likely scenarios of technology development are presented. The activities of national and regional companies implementing fiber long haul networks are also highlighted, along with an analysis of the market and regulatory forces affecting network evolution. Volume 3 presents advanced fiber optic network concept definitions. Inter-LATA traffic is quantified and forms the basis for the construction of 11-, 15-, 17-, and 23-node networks. Using the technology projections from Volume 2, a financial model identifies cost drivers and determines circuit mile costs between any two LATAs. A comparison of fiber optics with alternative transmission concludes the report.

Source record↗
NASA NTRS1983

Great prospects for fiber optics sensors

Fiber optic sensors provide noise immunity and galvanic insulation at the measurement point. Interest in such sensors is increasing for these reasons. In the United States sales are expected to increase from 12 million dollars in 1981 to 180 million in 1991. Interferometric sensors based on single modus fibers deliver extremely high sensitivity, while sensors based on multi-modus fibers are more easily manufactured. The fiber optic sensors which are available today are based on point measurements. Development of fiber optic sensors in Norway is being carried out at the Central institute and has resulted in the development of medical manometers which are now undergoing clinical testing.

Hansen, T. E.↗
NASA NTRS1994

Optical Fibers Would Sense Local Strains

Proposed fiber-optic transducers measure local strains. Includes lead-in and lead-out lengths producing no changes in phase shifts, plus short sensing length in which phase shift is sensitive to strain. Phase shifts in single-mode fibers vary with strains. In alternative version, multiple portions of optical fiber sensitive to strains characteristic of specific vibrational mode of object. Same principle also used with two-mode fiber.

Egalon, Claudio O.↗
NASA NTRS2000

Fiber optic temperature sensor

A fiber optic temperature sensor uses a light source which transmits light through an optical fiber to a sensor head at the opposite end of the optical fiber from the light source. The sensor head has a housing coupled to the end of the optical fiber. A metallic reflective surface is coupled to the housing adjacent the end of the optical fiber to form a gap having a predetermined length between the reflective surface and the optical fiber. A detection system is also coupled to the optical fiber which determines the temperature at the sensor head from an interference pattern of light which is reflected from the reflective surface.

Sawatari, Takeo↗
NASA NTRS1999

Fiber optic temperature sensor

A fiber optic temperature sensor uses a light source which transmits light through an optical fiber to a sensor head at the opposite end of the optical fiber from the light source. The sensor head has a housing coupled to the end of the optical fiber. A metallic reflective surface is coupled to the housing adjacent the end of the optical fiber to form a gap having a predetermined length between the reflective surface and the optical fiber. A detection system is also coupled to the optical fiber which determines the temperature at the sensor head from an interference pattern of light which is reflected from the reflective surface.

Sawatari, Takeo↗
NASA NTRS1995

Lightweight Fiber Optic Gas Sensor for Monitoring Regenerative Food Production

In this final report, Physical Optics Corporation (POC) describes its development of sensors for oxygen, carbon dioxide, and relative humidity. POC has constructed a phase fluorometer that can detect oxygen over the full concentration range from 0 percent to 100 percent. Phase-based measurements offer distinct advantages, such as immunity to source fluctuation, photobleaching, and leaching. All optics, optoelectronics, power supply, and the printed circuit board are included in a single box; the only external connections to the fluorometer are the optical fiber sensor and a power cord. The indicator-based carbon dioxide sensor is also suitable for short-term and discrete measurements over the concentration range from 0 percent to 100 percent. The optical fiber-based humidity sensor contains a porous core for direct interaction of the light beam with water vapor within fiber pores; the detection range for the humidity sensor is 10 percent to 100 percent, and response time is under five minutes. POC is currently pursuing the commercialization of these oxygen and carbon dioxide sensors for environmental applications.

Schmidlin, Edward↗
NASA NTRS1994

Fiber optic probes for laser light scattering: Ground based evaluation for micgrogravity flight experimentation. Integrated coherent imaging fiber optic systems for laser light scattering and other applications

The research work presented in this report has established a new class of backscatter fiber optics probes for remote dynamic light scattering capability over a range of scattering angles from 94 degrees to 175 degrees. The fiber optic probes provide remote access to scattering systems, and can be utilized in either a noninvasive or invasive configuration. The fiber optics create an interference free data channel to inaccessible and harsh environments. Results from several studies of concentrated suspension, microemulsions, and protein systems are presented. The second part of the report describes the development of a new technology of wavefront processing within the optical fiber, that is, integrated fiber optics. Results have been very encouraging and the technology promises to have significant impact on the development of fiber optic sensors in a variety of fields ranging from environmental monitoring to optical recording, from biomedical sensing to photolithography.

Dhadwal, Harbans Singh↗
NASA NTRS2000

Reduced Gravity Zblan Optical Fiber

Two optical fiber pullers have been designed for pulling ZBLAN optical fiber in reduced gravity. One fiber puller was designed, built and flown on board NASA's KC135 reduced gravity aircraft. A second fiber puller has been designed for use on board the International Space Station.

Tucker, Dennis S.↗
NASA NTRS1983

Fiber optics for astronomical spectroscopy - The Medusa Spectrograph

An instrument has been built to obtain simultaneous spectra of 32 objects in the field of view of the Steward Observatory 2.3 m telescope. Short lengths of optical fiber are used to bring light from galaxy images at the focus of the telescope into a line at the spectrograph slit. This multi-fiber aperture plate instrument has been dubbed the Medusa Spectrograph. The Medusa is now producing spectra of about 100 galaxies per clear night. An optimized version of the instrument called the MX Spectrometer is being constructed to record spectra at a higher rate. This new instrument will have remotely positioned fibers under computer control. A Charge Coupled Device will be used as the spectrograph detector to allow sky subtraction, give increased dynamic range and provide more accurate wavelength calibration. Transmission characteristics of some commercial fibers are discussed, and the microlens optics used to match the telescope and the spectrograph to the fibers to avoid focal ratio degradation are described.

Hill, J. M.↗
NASA NTRS1983

Fiber optic crossbar switch for automatically patching optical signals

A system for automatically optically switching fiber optic data signals between a plurality of input optical fibers and selective ones of a plurality of output fibers is described. The system includes optical detectors which are connected to each of the input fibers for converting the optic data signals appearing at the respective input fibers to an RF signal. A plurality of RF to optical signal converters are arranged in rows and columns. The output of each of the optical detectors are each applied to a respective row of optical signal converted for being converters back to an optical signal when the particular optical signal converter is selectively activated by a dc voltage.

Bell, C. H.↗
NASA NTRS1987

Fiber optics: A research paper

Some basic aspects concerning fiber optics are examined. Some history leading up to the development of optical fibers which are now used in the transmission of data in many areas of the world is discussed. Basic theory of the operation of fiber optics is discussed along with methods for improving performance of the optical fiber through much research and design. Splices and connectors are compared and short haul and long haul fiber optic networks are discussed. Fiber optics plays many roles in the commercial world. The use of fiber optics for communication applications is emphasized.

Drone, Melinda M.↗
NASA NTRS1982

Multiple object fiber optic spectroscopy

The Steward Observatory of the University of Arizona employs short optical fiber lengths to bring light from galaxy images at the 2.3 m telescope's focus to a line along a spectrograph slit, thereby obtaining simultaneous spectra of many objects of the field of view. After describing this instrument, attention is given to the development of an improved version through which efficiency gains will be obtained by remotely positioning the fibers under computer control and by correctly matching fiber outputs to the spectrograph optics. A CCD will replace the presently employed image tube and photographic plate detector system, in order to permit sky subtraction, yield increased dynamic range, and provide more accurate wavelength calibration due to the detector's fixed format.

Hill, J. M.↗
NASA NTRS1982

Multimode fiber optic wavelength division multiplexing

Optical wavelength division multiplexing (WDM) systems, with signals transmitted on different wavelengths through a single optical fiber, can have increased bandwidth and fault isolation properties over single wavelength optical systems. Two WDM system designs that might be used with multimode fibers are considered and a general description of the components which could be used to implement the system are given. The components described are sources, multiplexers, demultiplexers, and detectors. Emphasis is given to the demultiplexer technique which is the major developmental component in the WDM system.

Spencer, J. L.↗
NASA NTRS1982

Tutorial on multimode fiber optic wavelength division multiplexing

Optical wavelength division multiplexing (WDM) systems, with signals transmitted on different wavelengths through a single optical fiber, can have increased bandwidth and fault isolation properties over single wavelength optical systems. This paper considers two WDM system designs that might be used with multimode fibers and gives a general description of the components which could be used to implement the system. The components described are sources, multiplexers, demultiplexers, and detectors. Emphasis is given to the demultiplexer technique which is the major developmental component in the WDM system.

Spencer, J. L.↗
NASA NTRS1981

Fiber optic accelerometer

Low-cost, rugged lightweight accelerometer has been developed that converts mechanical motion into digitized optical outputs and is immune to electromagnetic and electrostatic interferences. Instrument can be placed in hostile environment, such as engine under test, and output led out through miscellany of electrical fields, high temperatures, etc., by optic fiber cables to benign environment of test panel. There, digitized optical signals can be converted to electrical signals for use in standard electrical equipment or used directly in optical devices, such as optical digital computer.

August, R. R.↗