• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 1973
  • 1004
  • 337
  • 264
  • 162
  • 148
  • 70
  • 67
  • 39
  • 38
  • 24
  • 17
  • 17
  • 17
  • 17
  • Tagged with
  • 5002
  • 836
  • 807
  • 609
  • 597
  • 569
  • 448
  • 442
  • 425
  • 357
  • 340
  • 310
  • 293
  • 269
  • 268
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.

Fabrication and Application of Capillary Optical Fiber and Microstructure Fiber

Wu, Kun-Shain 25 August 2011 (has links)
v Abstract This study was developed using fiber drawing tower to fabricate various types of capillary fiber and microstructured fiber. For example, different diameter sizes, different thickness, different internal diameter ratio of the capillary fiber and capillary tube, single ring and double ring hexagonal arrangement of the air-holes microstructured fiber. Trying different ways to create complex structures preform, we use the stack - drawing - cutting way, is now able to produce only simple pressure can be achieved by the complex structure of the preform, compared to drilling way, we can effectively reduce the production costs of 80%. Now successfully produced a single ring and double ring hexagonal air holes arranged in preform which has been drawn into standard fiber. Depending on the optical properties, we can use quartz tube with a row of self-developed method to produce most of the complex structure of the preform. However, each fiber is still not very uniform about the pores, which we need to improve in the manufacturing process of fiber drawing. Produce more diverse system and much homogeneous microstructured fiber as the goal. Application is to use the self-fabricated capillary tube, after processing, the production target into a low-loss device, then inject different materials within the devices, and do the different optical measurements for our devices.

Manufacturing Technique of 1D Lens Plastic Optical Fiber Array

chen, Ru-yan 06 August 2007 (has links)
The research is focus on manufacturing one dimension lens plastic optical fiber array, carrying out by electrostatic force was applied to shape polymer liquid from hemisphere into paraboloid or near cone shape. In manufacturing process, the lens will be slanted by electrostatic force, so we shorten the electrode to solve the problem, and shorten the distance between fiber and fiber to manufacture the most small volume of the fiber array. To combine the two methods, we can manufacture the high coupling efficiency of the one dimension lens plastic optical fiber array. Finally, the above improved strategies are verified by the simulation and experimental results.

Theoretical and Numerical Study of Fiber Modes with Arbitrary Axially Symmetric Index Profiles

Fang, Ching-Wei 03 July 2002 (has links)
Abstract There have been many studies on model characteristics of optical fibers since 1970. In the past twenty years we have seen changes in the index profiles and operating parameters (such as the carrier wavelength and fiber dispersion) of the fibers. We shall expect some change in the future as well. In this thesis we propose a 2nd-order coupled transverse magnetic field ordinary differential equations and associated boundary conditions for analyzing fiber modes with complex index profiles. Using finite-difference approximation, we convert the equations into matrix eigenvalue-eigenvector equations. These are then numerical solved (suing many commercial numerical softwares such as Matlab) to obtain propagation constants and field distribution inside the fibers. We shall show that our method do not require the use of cylindrical functions nor will the computation increase due to the increase of complexity in the index profile. In addition to finite-difference approximation, we may expand the model solutions in terms of elementary functions. In this thesis we computed many commercially available optical fibers such as 8/125, 9/125 step index fibers and 50/125, 62.5/125 graded index fibers. We compared our results against exact solution (the step index case) and found that we have converging solutions as we reduce the fiber sampling grid size £Gx. The difference in propagation constant is less than 0.1% when £Gx is < £f/6 .

Modal Analysis of Multi-Layer Cylindrical Dielectric Waveguides

Lin, Ming-Chong 01 July 2003 (has links)
Since 1970, there have been many analytic theories studying waveguide modes in optical fibers. As the years progressed, the structure of optical fiber and its characteristics have undergone many changes. In recent years, the methods of analysis have also evolved into a more numerical style, such as the finite element and finite difference approach. In this thesis, we propose a semi-analytic, coupled Ez and Hz method for solving a multiple layered piecewise constant cylindrical dielectric waveguides. In our mathematical model, we are able to handle any arbitrary layered structure, in particular, the step-index fiber, W-type fiber, and dielectric tubes. Within each layer, we express the azimuthal field components in terms of Bessel functions whose coefficients are determined by two pairs of Ez and Hz components that define the layer. By equating the transverse fields (above) on either side of each layer interface the coupled field equations are derived. The field components are either real, or purely imaginary, this allows us to formulate our matrix in real arithmetic. Further simplification is possible by using the Wronskians of the Bessel functions. The resulting matrices are both real and symmetric, which is consistent with the reciprocity principle. Compared to the traditional formulation from the early 1970s, we have reduced the variables by half and extended the formulation to include any arbitrary number of layers. Numerous numerical results are presented in this thesis for all three types of fiber previously mentioned. Both lower-order modes as well as higher-order modes including TE, TM, HE, and EH modes are presented and discussed. Our formulations are compared to that of textbook formulas for the simple two-layered step index fiber, and are found to be identical.

Fiber optic sensing technology for measuring in-cylinder pressure in automotive engines

Bae, Taehan 30 October 2006 (has links)
A new fiber optic sensing technology for measuring in-cylinder pressure in automotive engines was investigated. The optic sensing element consists of two mirrors in an in-line single mode fiber that are separated by some distance. To withstand the harsh conditions inside an engine, the Fiber Fabry-Perot Interferometer (FFPI) element was coated with gold and copper. The metal-protected fiber sensor was embedded into a small cut in the metal casing of the spark plug. At first, the sensing element was dipped in liquid gold and cured. Then the gold-coated fiber sensor was electroplated with copper. Finally, the metal-coated fiber sensor was embedded in the spark plug. The spark-plug-embedded FFPI sensor was monitored using a signal conditioning unit. Field tests were carried out in a 3-cylinder automotive engine with a piezoelectric pressure sensor as a reference transducer up to about 3500 rpm. The fiber optic sensor data generally matched those measured by the piezoelectric reference sensor. The use of a Vertical Cavity Surface Emitting Laser (VCSEL) diode as a light source in an FFPI optic sensor system was investigated. Reflected light from the FFPI sensing element was used to measure the optical path difference. With a 1550nm VCSEL as the light source in a 12mm cavity length Fiber Fabry-Perot Interferometer, spectral characteristics were examined to determine the proper combination of dc bias current, modulation current amplitude and modulation frequency. Single VCSEL operation and regular fringe patterns were achieved. The laser tuning was -41.2 GHz/mA and was determined from measurements of the shift in the spectral peak of the VCSEL diode output as a function of dc bias current. By testing the fringe movement as the FFPI sensor was heated, the temperature tuning coefficient for the optical length was determined to be 11 x 10-6 ºC. The results of these experiments indicate that the use of VCSEL diode as a light source for the FFPI sensor offers a viable alternative to the use of Distributed Feedback (DFB) laser diodes for monitoring at a lower bias current and modulating current amplitude.

Extremely Compact High-Power Er3+-Yb3+-Codoped Phosphate Glass Fiber Lasers

Li, Li January 2005 (has links)
Extremely compact high-power fiber lasers operating at eye-safe telecom wavelength of 1.5 μm have been achieved by systematic experimental studies. Heavily Er3+-Yb3+-codoped phosphate glasses have been chosen as the host glass for our fibers and 1.5 μm lasers have been realized when pumped with 975 nm laser diodes.The first short-length cladding-pumped fiber laser with watt-level CW output power has been demonstrated by an 11-cm-long doped step-index phosphate fiber. Without active cooling, 1.5 W output power at 1535 nm has been obtained.Thermoelectric cooler has been used for heavily doped phosphate step-index fibers. A dual-end-pumped actively cooled fiber laser has generated more than 11 W CW output power at 1535 nm from an 11.9 cm long active fiber. A fully 3-dimensional thermal analysis has been performed to calculate the internal temperature distribution of the short-length fiber laser and the simulated results have been experimentally verified.Phosphate glass microstructured optical fibers (MOFs) with large active cores have been fabricated. The first demonstrated short phosphate MOF laser has generated > 3 W single-mode CW output power from an 11-cm-long fiber. The impacts of depressed-core-index and annealing upon MOF's modal property have been systematically investigated. Extremely compact high-power fiber laser is demonstrated by a heavily doped MOF laser and > 4.5 W single-mode CW output power is delivered from a 3.5 cm long fiber. Finally, a high-power single-frequency fiber laser is realized by splicing a FBG with a 3.8 cm long MOF, which achieves > 2 W single-frequency output power.

Design and implementation of a FM audio channel in an optical fiber communication system

Repellin, L., 1949- January 1978 (has links)
No description available.

Electronic aspects in the design and implementation of an analog and a digital fiber optical communication system / Terminal design and implementation of an analog and a digital fiber optical communication system.

Redman, Mark D. January 1977 (has links)
No description available.

Optical diffuse reflectance and transmittance from an anistropically scattering finite blood medium.

Reynolds, Larry Owen. January 1975 (has links)
Thesis (Ph.D.)--University of Washington.

A durability and utility analysis of EFPI fiber optic strain sensors embedded in composite materials for structural health monitoring /

Haskell, Adam Benjamin, January 2006 (has links) (PDF)
Thesis (M.S.) in Civil Engineering--University of Maine, 2006. / Includes vita. Includes bibliographical references (leaves 175-177).

Page generated in 0.0635 seconds