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Measurement of Optical Fiber Bandwidth in the Frequency Domain

Description: Abstract: The design, evaluation, and performance of a system for determining the magnitude of the transfer function (hence, the bandwidth) of a multimode optical fiber are presented. The system operates to about 1450 MHz using a tracking generator/spectrum analyzer combination for narrowband detection. It is constructed, almost entirely, from commercially available components. The system is less complex and easier to use than an equivalent time domain system and the measurement precision is comparable. Background information on time and frequency domain specifications, fiber bandwidth limitations, and alternate frequency domain techniques is also presented.
Date: September 1981
Creator: Day, G. W.
Partner: UNT Libraries Government Documents Department

The Characterization of Optical Fiber Waveguides: A Bibliography with Abstracts, 1970-1980

Description: Abstract: This bibliography contains approximately 450 citations of papers concerning the characterization of optical fiber waveguides. Papers from scientific journals, trade journals and conferences are included along with book chapters. The citations of organized by parameter measured and measurement method. Where published abstracts are available they are included.
Date: June 1981
Creator: Day, G. W.
Partner: UNT Libraries Government Documents Department

Fault warning device using fiber-optic partial discharge sensor for prevention of destructive arc faults in metal-clad electrical switchgear and bus. [Semiannual report, May 1 - October 31, 1999]

Description: Progress made and problems encountered so far is discussed with reference to the Statement of Work which was submitted as part of the grant application. This work plan breaks down the project into fourteen numbered tasks grouped into three phases: Development of Improved Sensor Materials (Phase 1), Laboratory Testing of Improved Prototype on 15 kV Switchgear (Phase 2),and Field Testing of Beta Prototype and Start of Commercialization (Phase 3).
Date: December 2, 1999
Creator: Forsyth, Keith W.
Partner: UNT Libraries Government Documents Department

Photonic Power Delivery Through Optical Fiber Using Very High Power Laser Diode Arrays

Description: Described is a system that will provide isolated electric power for a circuit that drives the core reset of a pulsed power modulator. This can be accomplished by coupling light from a number of diode laser bars to bundles of 200 um multimode optical fibers. This is then coupled to photo-voltaic power converters that will deliver 16 V 29mA of electricity from 1 watt of optical power. Spot size at the bundle face is a Gausian ellipse with a major axis of 1.4 mm radius and a minor axis of four bundles of 12 fibers generating a total of 24 W of electrical power. Various schemes are used to maximize coupling into the optical filber while limiting the number of optical components, and comparing components such as fresnel and aspheric lenses and lens ducts for effectiveness and cost. This will provide a completely isolated low power source for high voltage, high current environments where tradional isolation techniques yield inadequate isolation or prove too cumbersome.
Date: May 1, 1999
Creator: Heino, Matthew & Saethre, Robert
Partner: UNT Libraries Government Documents Department

A FEMTOSECOND-LEVEL FIBER-OPTICS TIMING DISTRIBUTION SYSTEM USING FREQUENCY-OFFSET INTERFEROMETRY

Description: An optical fiber-based frequency and timing distribution system based on the principle of heterodyne interferometry has been in development at LBNL for several years. The fiber drift corrector has evolved from an RF-based to an optical-based system, from mechanical correctors (piezo and optical trombone) to fully electronic, and the electronics from analog to fully digital, all using inexpensive off-the-shelf commodity fiber components. Short-term optical phase jitter and long-term phase drift are both in the femtosecond range over distribution paths of 2 km or more.
Date: October 17, 2009
Creator: Staples, J.W.; Byrd, J.; Doolittle, L.; Huang, G. & Wilcox, R.
Partner: UNT Libraries Government Documents Department

Propagation of 2.5 Gb/s Asynchronous, Concurrent, Optical CDMA Signals Through a 214 Kilometer Fiber Optic Link

Description: The propagation of optical Code Division Multiple Access (CDMA) signals was studied by computer simulation. Group velocity dispersion produces the worst impairment. With dispersion management, the decoder successfully recovers the signals, even in the presence of severe multi-access interference.
Date: March 16, 2000
Creator: Mendez, A.J.; Feng, H.X.C.; Heritage, J.P.; Morookian, J. & Gagliardi, R.M.
Partner: UNT Libraries Government Documents Department

Compact, low-crosstalk, WDM filter elements for multimode ribbon fiber data links

Description: We have been developing the optical components for a source-routed wavelength division multiplexed (WDM) computer interconnect fabric that uses multi-mode fiber ribbon cable as the transmission medium. We are developing wavelength selectable VCSEL transmitters, interference filters, and a compact broadcast element. Here we report on key results from our interference filter development activities. Our WDM filter approach is based upon post-market machining of the commercially available molded plastic �MT� fiber ribbon connector. We use III-IV semiconductors grown by MBE or MOCVD as the filter materials. The high indices of our thin film materials enable us to use multimode fiber and maintain narrow passbands without the need for micro-optics. We have fabricated both 2-port and 3-port devices based upon this approach. Our current work focuses on 2-port WDM filters suitable for a broadcast and select architecture. Our single-cavity Fabry- Perot (FP) filters have demonstrated insertion losses of < 2 dB for 4 nm passbands. The maximum crosstalk suppression for the single-cavity FP filters is 18dB To improve crosstalk suppression beyond that attainable with the Lorentzian lineshapes of the single-cavity FP we have investigated some multiple-cavity Fabry-Perot (MC-FP) designs which have a spectral response with a flatter top and sharper passband edges. Filter passband edge sharpness can be quantified by the ratio of the filter 3 dB bandwidth to 18 dB bandwidth This ratio is 0.48 for our multi-cavity filter, three times sharper than the single-cavity FP devices. This device provides a 5 nm tolerance window for component wavelength variations (at 1 dB excess loss) and is suitable for 10 nm channel spacing with 23 dB crosstalk suppression between adjacent channels. The average insertion loss for the MC-l? devices is 1.6 dB. (Average of insertion losses for the 12 fibers in a filter module.) Our current MC-FP filters have a 3-dB width ...
Date: January 1, 1999
Creator: Deri, R J; Emanuel, M A; Garrett, H H; Krol, D M; Larson, M Pocha, M D; Lowry, M E et al.
Partner: UNT Libraries Government Documents Department

Far-field radiation from a cleaved cylindrical dielectric waveguide

Description: Angular spread in the far-field radiation pattern of a cleaved dielectric waveguide is determined from the modal structure at the surface of the waveguide using the Smythe vector integral formulation. Essential features: First, a mode exists in the fiber that has no wavelength cutoff--the so-called HE{sub 11} mode. This mode arises when non-azimuthal angular dependence of the incoming radiation is present. Second, the energy flow from this hybrid mode fills the fiber face and is not annularly shaped as opposed to the symmetric TE and TM modes. Third, the HE{sub 11} mode is not polarization dependent in contrast to the TE and TM modes. Fourth, for small differences in the refractive indices between the core and cladding regions, only the HE{sub 11} mode will be supported until the next modes appear around 3.33{lambda}. At this point, three new modes can propagate and the model structure of the radiation becomes more complicated. Fifth, the far-field radiation pattern will have negligibly small angular dependence in the phases of the vector fields when only the lowest mode is present; the amplitude has an overall angular dependent form factor. Furthermore, when other modes are present (above 3.33{lambda}), the phase of the vector fields will acquire an angular dependence.
Date: July 9, 1996
Creator: Cerjan, C.
Partner: UNT Libraries Government Documents Department

Production and preliminary testing of multianalyte imaging sensor arrays

Description: This report covers the production and preliminary testing of fiber optic sensors that contain a discrete array of analyte specific sensors on their distal ends. The development of the chemistries associated with this technology is covered elsewhere.
Date: November 1, 1994
Creator: Richards, J.B.; Brown, S.B.; Milanovich, F.P.; Healey, B.G.; Chadha, S. & Walt, D.R.
Partner: UNT Libraries Government Documents Department

Multiple-beam pulse shaping and preamplification

Description: Glass fusion laser systems typically use a master oscillator-power amplifier (MOPA) architecture, where control of the optical pulse temporal and spatial parameters is accomplished mainly in the master oscillator and low power optics. The pulses from this low power ``front end`` are amplified in the power amplifier, which modifies the pulse shape temporally and spatially. Nonlinear frequency conversion crystals following the amplifier further change the pulse before it reaches the target. To effectively control the optical pulse on target for different types of experiments, and compensate for nonlinearity in the preceding optics, the front end system must be versatile enough to easily control many pulse parameters over a large range. The front end pulse generation system described in this article represents a new approach to this problem. The proposed National Ignition Facility (NIF) has 192 beamlines, each of which requires an input pulse of up to 12 Joules in around 4 ns equivalent square pulse length. Considerations of laser architecture for supplying each of these beamlines from a central oscillator system were crucial in the design of the front end. Previous lasers have used bulk optics to split a single oscillator signal and report beams to multiple amplifier chains. A key idea in the current design is to replace bulk optic transport with fibers, eliminating large opto-mechanical subsystems. Another important concept is convenient pulse forming using low voltage integrated optic modulators. The integrated optic and fiber optic concepts resulted in the current pulse generation designs for NEF. An important advantage is that each of the beamlines can have an independently controlled temporal pulse shape, which provides for precise balance of instantaneous power on target.
Date: November 9, 1994
Creator: Wilcox, R.B.; VanWonterghem, B.W.; Burkhart, S.C. & Davin, J.M.
Partner: UNT Libraries Government Documents Department

The use of an intermediate wavelength laser for alignment to inertial confinement fusion targets

Description: The conceptual design of the National Ignition Facility (NIF) 192 beam laser incorporates a low-power alignment beam injected in the pinhole plane of the final spatial filter with a wave length intermediate between the 1053 mn laser output and the 351 mn frequency-converted beam that illuminates the target Choosing the specific wavelength for which the spatial filter plane is reimaged in the same target chamber plane as the frequency-converted main laser pulse, achieves optimum accuracy without the need for additional means to insure precise overlap between the two beams. Insertion of the alignment beam after the last laser amplifier also allows alignment to the target while the amplifiers are still cooling from a previous shot.
Date: September 21, 1995
Creator: English, R.E. Jr.; Seppala, L.G.; Vann, C.S. & Bliss, E.S.
Partner: UNT Libraries Government Documents Department

Non-contact tamper sensing by electronic means

Description: This invention is comprised of a tamper-sensing system for an electronic tag which is to be fixed to a surface of an article, the tamper-sensing system comprising a capacitor having two non- contacting, capacitively-coupled elements. Fixing of the body to the article will establish a precise location of the capacitor elements and relative to each other. When interrogated, the tag will generate a tamper-sensing signal having a value which is a function of the amount of capacity of the capacitor elements. The precise relative location of the capacitor elements cannot be duplicated if the tag is removed and affixed to a surrogate article having a fiducial capacitor element fixed thereto. A very small displacement, in the order of 2-10 microns, of the capacitor elements relative to each other if the tag body is removed and fixed to a surrogate article will result in the tamper-sensing signal having a different, and detectable, value when the tag is interrogated.
Date: December 31, 1991
Creator: Gritton, D.G.
Partner: UNT Libraries Government Documents Department

Dynamic Strain on Thin Diaphragms of a Mercury Target During 800-MeV Proton Thermal Shock Tests

Description: Extrinsic Fabry-Perot Interferometric fiber optic sensors were used to measure dynamic strains on thin diaphragms of a liquid mercury target, which was subjected to intense 800-MeV proton thermal shock tests. The mercury target is engineered with very thin end plates or diaphragms (either 0.6 mm or 1.9 mm) for studying large strain effects. During thermal shock tests, the mercury in the target interacted with an intense pulsed beam of 2.4x10{sup 13 protons}. The resulting pressure waves lead to large strains exceeding 250 microstrains on a 0.6-mm diaphragm. Significant factors relative to the accuracy of strain measurements are emphasized, such as the sensor air gap, alignment of sensors, and frequency response of the strain instrument. In this paper, dynamic strains measured on thin diaphragms are described and discussed.
Date: November 13, 1999
Creator: Allison, S.W.; Andriulli, J.B.; Cates, M.R.; Earl, D.D.; Haines, J.R.; Morrissey, F.X. et al.
Partner: UNT Libraries Government Documents Department

A fiber optic wind vane

Description: A Cooperative Research and Development Agreement (CRADA) between Met One Instruments, Incorporated (Met One) and Westinghouse Savannah River Company (WSRC) was made to develop and test a fiber optic measurement-based wind vane. Some advantages of using fiber optic technology for a wind vane include protection against lightning-induced electrical surges and radio-frequency interference, suitability for use in explosive environments, and a longer field life. A prototype fiber optic wind vane was built by Met One and tested by WSRC. Wind tunnel test results indicated that the vane is very sensitive to low wind speeds (< 0.15 meter per second) although the resolution of the sensor (1.4 degrees) is higher than typical wind vanes. A side-by-side field test with a conventional commercial wind vane indicated that the fiber optic wind vane performed well and even outperformed the conventional sensor during low wind speed conditions. The field test also indicated that the fiber optic sensor is a viable instrument although some modifications are required before the sensor can be readily commercialized.
Date: February 1, 1997
Creator: Parker, M.J. & Heverly, M.
Partner: UNT Libraries Government Documents Department

Development of multianalyte sensor arrays for continuous monitoring of pollutants

Description: Industrial development has led to the release of numerous hazardous materials into the environment posing a potential threat to surrounding waters. Environmental analysis of sites contaminated by several chemicals calls for continuous monitoring of multiple analytes. Monitoring can be achieved by using imaging bundles (300--400 {micro}m in diameter), containing several thousand individual optical fibers for the fabrication of sensors. Multiple sensor sites are created at the distal end of the fiber by immobilizing different analyte-specific fluorescent dyes. By coupling these imaging fibers to a charge coupled device (CCD), one has the ability to spatially and spectrally discriminate the multiple sensing sites simultaneously and hence monitor analyte concentrations.
Date: January 1, 1995
Creator: Milanovich, F.P.; Richards, J.B.; Brown, S.B.; Healey, B.G.; Chadha, S. & Walt, D.
Partner: UNT Libraries Government Documents Department

A Laser Metrology/Viewing System for ITER In-Vessel Inspection

Description: This paper identifies the requirements for a remotely operated precision laser ranging system for the International Thermonuclear Experimental Reactor. The inspection system is used for metrology and viewing, and must be capable of achieving submillimeter accuracy and operation in a reactor vessel that has high gamma radiation, high vacuum, elevated temperature, and magnetic field levels. A coherent, frequency modulated laser radar system is under development to meet these requirements. The metrology/viewing sensor consists of a compact laser-optic module linked through fiberoptics to the laser source and imaging units, located outside the harsh environment. The deployment mechanism is a remotely operated telescopic mast. Gamma irradiation up to 10{sup 7} Gy was conducted on critical sensor components with no significant impact to data transmission, and analysis indicates that critical sensor components can operate in a magnetic field with certain design modifications. Plans for testing key components in a magnetic field are underway.
Date: December 31, 1997
Creator: Spampinato, P.T.; Barry, R.E.; Chesser, J.B.; Menon, M.M.; Dagher, M.A. & Slotwinski, A.
Partner: UNT Libraries Government Documents Department

Photoemission Phenomena on CEBAF RF Windows at Cryogenic Temperatures

Description: This paper reports on the photoemission observed during the tests on a single-cell 1500 MHz niobium cavity with a polycrystalline alumina rf interface window operated at 2K. The light emission from the window at 2K was detected using a multi-channel fiber optics/PMT system and recorded with a 100 Ms/sec acquisition system. The spectral composition of two types of discharges has been measured. The results indicate that both broadband and narrow-band emissions are present, depending on the discharge type.
Date: May 1, 1993
Creator: Powers, T.; Kneisel, P. & Vaidya, M.
Partner: UNT Libraries Government Documents Department

Light absorption cell combining variable path and length pump

Description: This invention is comprised of a device for use in making spectrophotometric measurements of fluid samples. In particular, the device is a measurement cell containing a movable and a fixed lens with a sample of the fluid therebetween and through which light shines. The cell is connected to a source of light and a spectrophotometer via optic fibers. Movement of the lens varies the path length and also pumps the fluid into and out of the cell. Unidirectional inlet and exit valves cooperate with the movable lens to assure a one-way flow of fluid through the cell. A linear stepper motor controls the movement of the lens and cycles it from a first position closer to the fixed lens and a second position farther from the fixed lens, preferably at least 10 times per minute for a nearly continuous stream of absorption spectrum data.
Date: December 31, 1992
Creator: Prather, W.S.
Partner: UNT Libraries Government Documents Department

A fiber optic synchronization system for LUX

Description: The LUX femtosecond light source concept would support pump-probe experiments that need to synchronize laser light pulses with electron-beam-generated X-ray pulses to less than 50 fs at the experimenter endstations. To synchronize multiple endstation lasers with the X-ray pulse, we are developing a fiber-distributed optical timing network. A high frequency clock signal is distributed via fiber to RF cavities (controlling X-ray probe pulse timing) and mode-locked lasers at endstations (controlling pump pulse timing). The superconducting cavities are actively locked to the optical clock phase. Most of the RF timing error is contained within a 10 kHz bandwidth, so these errors and any others affecting X-ray pulse timing (such as RF gun phase) can be detected and transmitted digitally to correct laser timing at the endstations. Time delay through the fibers will be stabilized by comparing a retro-reflected pulse from the experimenter endstation end with a reference pulse from the sending en d, and actively controlling the fiber length.
Date: June 30, 2004
Creator: Wilcox, R.B.; Staples, J.W. & Doolittle, L.R.
Partner: UNT Libraries Government Documents Department

Summary of innovative concepts for industrial process improvement: An experimental technology exchange

Description: This document is a compilation of one-page technical briefs that summarize the highlights of thirty-eight innovations that were presented at the seventh Innovative Concepts Fair, held in Denver, Colorado on April 20--21, 1995. Sixteen of the innovations were funded through the Innovative Concepts Program, and twenty-two innovations represent other state or federally funded programs. The concepts in this year`s fair addressed innovations that can substantially improve industrial processes. Each tech brief describes the need for the proposed concept; the concept being proposed; and the concept`s economics and market potential, key experimental results, and future development needs. A contact block is also included with each flier.
Date: August 1, 1995
Creator: Conger, R. L.; Lee, V. E. & Buel, L. M.
Partner: UNT Libraries Government Documents Department