Thesis (Ph. D.)--University of Washington, 2004. / Vita. Includes bibliographical references (leaves 140-147).

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Parametric design models were created to optimize cable sensitivities in a structural health-monitoring system. Experiments were also conducted to determine the sensitivity of a working system. The system consists of time domain reflectometry (TDR) signal processing equipment and specially designed sensing cables. The TDR equipment sends a high-frequency electric pulse (in the gigahertz range) along the sensing cable. Any change in electric impedance along the cable reflects some portion of the electric pulse back to the TDR equipment. The time delay, amplitude, and shape of the reflected pulse provides the means to respectively locate, determine the magnitude, and indicate the nature of the change in impedance. The change in the sensing cable impedance may be caused by cable elongation (change in resistance), shear deformation (change in capacitance), corrosion of the cable or the materials around the cable (change in inductance), etc. The sensing cables are an essential part of the health-monitoring system because the cable design parameters determine the cable impedance sensitivity to structural changes. By using parametric design models, the optimum cable parameters can be determined for specific cases and used to select or design an appropriate cable. Proof-of-concept and resolution experiments were also conducted to provide, respectively, verification and sensitivity of the system. / Master of Science

This paper describes how water content reflectometers (WCRs) were analyzed to develop a calibration equation. Time domain reflectometry (TDR) technique is the most prevalent method in in-situ moisture monitoring; and WCR is a type of low frequency TDR sensors, which is sensitive to soil type. Developing soil-specific calibration and investigating different environmental effects on WCR calibration is important. This study focused on investigation of the soil dry density and temperature effects on WCR calibration in RMA soil. Two series of tests to develop soil-specific calibration with dry density and temperature offset were conducted. Results from testing program showed that WCR response was positive related to volumetric water content, dry density, and temperature. Equations were developed to illustrate the response-density-temperature-moisture relation. Application to a field site was also presented to illustrate the difference in volumetric water contents obtained by using manufacturer method and the calibration procedure drawn in this paper. / text

A microwave reflectometer is an instrument to measure a complex ratio between reflected and incident waves at an input port of a uniform transmission line that is terminated in a Device Under Test (DUT). The conventional reflectometer is formed by a four-port network with two ports connected to a microwave source and DUT, and the remaining ports coupled to a heterodyne receiver which acts as a Complex Ratio Detector (CRT). By using the heterodyne receiver technique, the two microwave signals at the input to CRT are converted in the linear manner to an Intermediate Frequency (IF) of hundreds of kHz where they are processed using digital means. As the ratio of two original microwave signals has to be preserved at IF, a very advanced electronic circuitry is required to accomplish the linear conversion process. This complicated electronic circuitry leads to a large size of the conventional reflectometer and its high price tag. Many applications require compact-size and low-cost reflectometers. They can be built using N-port networks, with N being greater than 5, equipped only in scalar (power) detectors. The thesis describes the concept of a multi-port reflectometer which determines the complex reflection coefficient of DUT with the use of scalar detectors instead of the complex ratio detector. It is shown that this device can be designed using an assembly of linear circuits in the form of quadrature (Q) and/or divider (D) hybrids. Assuming ideal operation of these components, it is shown that the reflection coefficient of DUT can be determined using simple mathematical operations on the power values measured by scalar detectors. Alternatively, it can be obtained from the intersection of power circles in a complex reflection coefficient plane. These simple mathematical expressions can be used to obtain an approximate real-time operation of reflectometer. For more accurate results, the multi-port has to be calibrated using calibration standards. A review of full calibration methods for a multi-port reflectometer is presented. In order to obtain wideband performance, the multi-port reflectometer has to be formed by components all having wideband performance. To obtain its low manufacturing cost, these components should preferably be of planar format and lead to a full integration of reflectometer. The thesis investigates a variety of planar couplers and dividers which can offer wideband performances. However, not all of them can lead to a fully integrated multi-port reflectometer. In order to overcome this shortfall, a multilayer microstrip-slot technique is proposed and investigated to obtain wideband components that can lead to a full integration of multi-port reflectometer. It is demonstrated that through the use of multilayer microstrip-slot technique, ultra wideband microwave 3-dB couplers and two-way dividers of in-phase or out-of-phase type can be designed. It is shown that the chosen configurations of dividers are compatible with the 3-dB couplers so that a fully integrated reflectometer can be formed. This compatibility is accomplished through the use of suitably designed microstrip to slotline transitions. An attractive feature of the designed couplers and dividers is that they are of sub-wavelength size and thus are very compact. A fine operation of these components is demonstrated via full electromagnetic wave simulations and experimental tests over and ultra wide frequency band of 3.1 to 10.6 GHz. Rogers substrate RO4003 featuring a relative dielectric constant of 3.38 and a loss tangent of 0.0027 is chosen as a microwave substrate for the design of these components. The design and analysis are carried out with the commercially available full EM simulator CST Microwave Studio while the experimental tests are done with the Vector Network Analyser, HP8510C. By using these components, an ultra wideband complex ratio measuring unit (CRMU), which is the heart of a multi-port reflectometer, is designed. This CRMU is fully integrated and of compact size. Its operation over an ultra wide frequency band is demonstrated via simulations. A particular attention is paid to its real-time mode of operation. Using this mode of operation, the complex ratio of two waves can be displayed on an oscilloscope using an analog electronics performing simple mathematical operations on the measured powers by detectors. While discussing the operation of CRMU, the attention is paid to the location and spacing of power circles centres (q-points) which are used for geometrical interpretation of operation of this device. Good operation of CRMU in this approximate operation mode indicates that the device will operate very well when it is fully calibrated. For simulations of CRMU, CST Microwave Studio, Agilent’s Advanced Design System (ADS) and MATLAB software are applied. Having accomplished the successful design of CRMU, the last step includes the formation of a fully integrated multi-port reflectometer. To this purpose an extra circuitry including multilayer microstrip-slot 3-dB couplers is added to CRMU. The purpose of this additional circuitry is to reroute the incident and reflected signals from the DUT to the input ports of CRMU. A few configurations of multi-port relectometer formed by multilayer microstrip-slot couplers or dividers are investigated via simulations with respect to real-time mode of operation. Then, the best performing configuration is selected for the final development. The device is manufactured in Rogers RO4003 substrate. Its S-parameters are measured with HP8510C analyser and compared with the simulated values. Having obtained a relatively good agreement between the simulated and measured results, the device is calibrated using multiple calibration standards. Its operation is verified for selected DUTs by comparing the measured reflection coeffcients with those obtained using the conventional VNA (HP8510C) over an ultra wide frequency band. A relatively good agreement is obtained between the two sets of measured results. The obtained results prove that the multilayer microstrip-slot technology can successfully be used for the development of a compact low-cost and fully integrated UWB multi-port reflectometer. Because of its compact size and good electrical performance, this device can be used in many microwave sub-systems offering a limited space for implementation of microwave measurements. The thesis shows that the accomplished multi-port device can also be used to build UWB communication transceivers. The concept of such UWB transceivers is addressed in the final sections of this thesis.

This masters thesis is focusing on the issue of passive optic access networks. It is dealing with the limiting factors for broadband connections, especially attenuation of fibre optics and dispersion. It is also dealing with most commonly used standards of passive optic networks. It clarifies the issue of wavelength-division multiplexing, its advantages and disadvantages, used standards, various types of components for the WDM-networks, their characteristics, application etc. In the practical part of the work you can find the measuring and diagnostics of the passive optic network EPON. It contains measuring by the direct method OLTS, measuring by the Pon Power Meter and optic reflectometer OTDR. At the end I am dealing with the measuring of splitter in the rate of 1:16.

This project focuses on wavelength division multiplexing passive optical network (WDM-PON) supervision using optical time domain reflectometer (OTDR) for detection and localization of any fault occurred in optical distribution network. The objective is to investigate the impact of OTDR monitoring signal on the data transmission in the WDM-PON based on wavelength re-use system, where the same wavelength is assigned for both upstream and downstream to each end user. Experimental validation has been carried out to measure three different schemes, i.e. back-to-back, WDM-PON with and without OTDR connection by using 1xN and NxN arrayed waveguide gratings. Furthermore, a comprehensive comparison has been made to trace out the effect of the monitoring signal which is transmitted together with the data through the implemented setup. Finally, the result has confirmed that the OTDR supervision signal does not affect the data transmission. The experiment has been carried out at Ericsson AB, Kista.

Laser high-order harmonic generation in the presence of relatively weak interfering light is investigated. The interfering pulses intersect the primary harmonic-generating laser pulse at the laser focus. The interfering light creates a standing intensity and phase modulation on the field, which disrupts microscopic phase matching and shuts down local high harmonic production. Suppression of the 23rd harmonic (by two orders of magnitude) is observed when a counter-propagating interfering pulse of light is introduced. A sequence of counter-propagating pulses can be used to shut down harmonic production in out-of-phase zones of the generating volume to achieve quasi phase matching. Harmonic emission is enhanced in this case. A new high-power laser system with higher pulse energy has been constructed to further investigate quasi phase matching of high-order harmonics generated in difficult-to-ionize atomic gases (e.g., neon as opposed to argon). The new system can also be used to study harmonic generation in ions. A new counter-propagating beam produces a train of 5 pulses with regulated timing. In preliminary tests, the new system has produced high harmonics up to the 65th order in neon. This should increase with additional adjustments to the laser system. The high-order harmonics have also demonstrated to be useful for polarized reflectometry measurements of optical surfaces in the extreme ultraviolet (EUV) wavelength range.

A distributed sensor using an optical fiber for detecting and locating intruders over long perimeters (>10 km) is described. Phase changes resulting from either the pressure of the intruder on the ground immediately above the buried fiber or from seismic disturbances in the vicinity are sensed by a phase-sensitive optical time-domain reflectometer (φ−OTDR). Light pulses from a cw laser operating in a single longitudinal mode and with low (MHz/min range) frequency drift are injected into one end of the single mode fiber, and the backscattered light is monitored with a photodetector. In laboratory tests with 12 km of fiber on reels, the effects of localized phase perturbations induced by a piezoelectric fiber stretcher on φ−OTDR traces were characterized. In field tests in which the sensing element is a single mode fiber in a 3-mm diameter cable buried in an 8 to 18 inch deep, 4 inch wide trench in clay soil, detection of intruders on foot up to 15 ft from the cable line was achieved. In desert terrain field tests in which the sensing fiber is in a 4.5-mm diameter cable buried in a 1 ft deep, 2.5 ft wide trench filled with loose sand, high sensitivity and consistent detection of intruders on foot and of vehicles traveling down a road near the cable line was realized over a cable length of 8.5 km and a total fiber path of 19 km in real time. In a final series of field tests in clay soil, phase changes produced by the steps of a person walking up to 15 ft away from the buried cable were observed, and vehicles traveling at 10 mph were consistently detected up to 300 ft away. Based on these results, this technology may be regarded as a candidate for providing low-cost perimeter security for nuclear power plants, electrical power distribution centers, storage facilities for fuel and volatile chemicals, communication hubs, airports, government offices, military bases, embassies, and national borders.

A distributed sensor using an optical fiber for detecting and locating intruders over long perimeters (>10 km) is described. Phase changes resulting from either the pressure of the intruder on the ground immediately above the buried fiber or from seismic disturbances in the vicinity are sensed by a phase-sensitive optical time-domain reflectometer (φ−OTDR). Light pulses from a cw laser operating in a single longitudinal mode and with low (MHz/min range) frequency drift are injected into one end of the single mode fiber, and the backscattered light is monitored with a photodetector. In laboratory tests with 12 km of fiber on reels, the effects of localized phase perturbations induced by a piezoelectric fiber stretcher on φ−OTDR traces were characterized. In field tests in which the sensing element is a single mode fiber in a 3-mm diameter cable buried in an 8 to 18 inch deep, 4 inch wide trench in clay soil, detection of intruders on foot up to 15 ft from the cable line was achieved. In desert terrain field tests in which the sensing fiber is in a 4.5-mm diameter cable buried in a 1 ft deep, 2.5 ft wide trench filled with loose sand, high sensitivity and consistent detection of intruders on foot and of vehicles traveling down a road near the cable line was realized over a cable length of 8.5 km and a total fiber path of 19 km in real time. In a final series of field tests in clay soil, phase changes produced by the steps of a person walking up to 15 ft away from the buried cable were observed, and vehicles traveling at 10 mph were consistently detected up to 300 ft away. Based on these results, this technology may be regarded as a candidate for providing low-cost perimeter security for nuclear power plants, electrical power distribution centers, storage facilities for fuel and volatile chemicals, communication hubs, airports, government offices, military bases, embassies, and national borders.