International Telemetering Conference Proceedings / October 18-21, 2004 / Town & Country Resort, San Diego, California / The use of traditional telemetry decommutation equipment can be easily expanded to create a real-time pulse code modulation (PCM) telemetry data recorder. However, there are two areas that create unique demands where architectural investment is required: the PCM output stage and the storage stage. This paper details the efforts to define the requirements and limits of a traditional telemetry system when used as a real-time, multistream PCM data recorder with time tagging.

The Richtmyer-Meshkov Instability (RMI) (Commun. Pure Appl. Math 23, 297-319, 1960; Izv. Akad. Nauk. SSSR Maekh. Zhidk. Gaza. 4, 151-157, 1969) occurs due to an impulsive acceleration acting on a perturbed interface between two fluids of different densities. In the experiments presented in this thesis, single mode 3D RMI experiments are performed. An oscillating speaker generates a single mode sinusoidal initial perturbation at an interface of two gases, air and SF6. A Mach 1.19 shock wave accelerates the interface and generates the Richtmyer-Meshkov Instability. Both gases are seeded with propylene glycol particles which are illuminated by an Nd: YLF pulsed laser. Three high-speed video cameras record image sequences of the experiment. Particle Image Velocimetry (PIV) is applied to measure the velocity field. Measurements of the amplitude for both spike and bubble are obtained, from which the growth rate is measured. For both spike and bubble experiments, amplitude and growth rate match the linear stability theory at early time, but fall into a non-linear region with amplitude measurements lying between the modified 3D Sadot et al. model (Phys. Rev. Lett. 80, 1654-1657, 1998) and the Zhang & Sohn model (Phys. Fluids 9. 1106-1124, 1997; Z. Angew. Math Phys 50. 1-46, 1990) at late time. Amplitude and growth rate curves are found to lie above the modified 3D Sadot et al. model and below Zhang & Sohn model for the spike experiments. Conversely, for the bubble experiments, both amplitude and growth rate curves lie above the Zhang & Sohn model, and below the modified 3D Sadot et al. model. Circulation is also calculated using the vorticity and velocity fields from the PIV measurements. The calculated circulation are approximately equal and found to grow with time, a result that differs from the modified Jacobs and Sheeley's circulation model (Phys. Fluids 8, 405-415, 1996).

Kwok Chi Hang. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2006. / Includes bibliographical references. / Abstracts in English and Chinese. / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- All-Optical Signal Processing in Optical Communications --- p.2 / Chapter 1.2 --- Fiber-Based Optical Kerr Nonlinear Switches --- p.5 / Chapter 1.3 --- Highly Nonlinear Fibers --- p.6 / Chapter 1.4 --- Objectives and Scope of Study --- p.8 / Chapter 1.5 --- Summary --- p.9 / Chapter Chapter 2 --- Optical Nonlinearity --- p.14 / Chapter 2.1 --- Fiber Nonlinearity --- p.15 / Chapter 2.2 --- Dispersion --- p.21 / Chapter 2.3 --- Cross-Phase Modulation --- p.26 / Chapter 2.4 --- Cross-Polarization Modulation --- p.29 / Chapter Chapter 3 --- Fibers: The Nonlinear Media --- p.47 / Chapter 3.1 --- Average Dispersion --- p.48 / Chapter 3.2 --- Longitudinal Dispersion Map --- p.53 / Chapter 3.3 --- Nonlinear Refractive Index and Nonlinear Coefficient --- p.57 / Chapter 3.4 --- Electrostrictive Contribution --- p.62 / Chapter 3.5 --- List of the Fiber Properties --- p.66 / Chapter Chapter 4 --- Multi-Wavelength Nonlinear Signal Processing --- p.69 / Chapter 4.1 --- Challenge --- p.70 / Chapter 4.2 --- Applications --- p.72 / Chapter 4.3 --- Proposed System Application --- p.110 / Chapter Chapter 5 --- Conclusion and Future Work --- p.114 / Chapter 5.1 --- Comparisons between Proposed and Existing Approaches --- p.114 / Chapter 5.2 --- Conclusion of the Dissertation --- p.115 / Chapter 5.3 --- Prospects and Directions of Future Work --- p.117 / Appdenix A Numerical Model for Dispersion Calculation --- p.I / Appdenix B Simulation Model of Wide Band Cross-Polarization Switch --- p.III / Appdenix C Simulation Model of Spectral Filtering under XPM --- p.VI / List of Publications --- p.IX

In the literatures of investigating the coupling mechanism between laser diodes and fibers, Gaussian beam profile was used to describe the propagation of laser beams. But the real laser diode beams exist astigmatism. In order to understand the distributions of real laser diode beams, we used single-mode fiber interferometer to measure the near-field intensity and phase distributions of laser diodes. The nanometer aperture of taper fiber was used to scan through the horizontal and vertical directions across the maximal intensity point of the planes which were perpendicular to propagation axis to measure the intensity and phase distributions of laser diodes. In the measurement of phase distributions, these two single-mode fibers produced interference fringes through accepting laser beams. When the taper fiber scanned the optical field and the reference fiber kept a fixed distance from a laser diode for a stationary phase, the interference fringes shifted because of the phase difference of laser diodes change. In the measurement, in order to improve the stability of interference fringes and consider the aperture of taper fiber, we altered some experiment frameworks. There were four types of experimental framework. According to the experiment results of the near-field measurements, the measured beam widths along the horizontal and vertical directions at the laser diode facet were 4.11 £gm and 1.57 £gm respectively. The measured wavefront radius curvature were 6.59 £gm and 2.96 £gm in horizontal axis and vertical axis respectively. After Gaussian beam fitting, the beam widths along the horizontal and vertical directions at the laser diode facet were 4.04 £gm and 0.83 £gm respectively. The difference in beam widths between measured values and Gaussian fitting were 0.07 £gm and 0.74 £gm. The measured beam widths and the Gaussian beam curve fitting had similar results. We could see that the beam spread tendency in the z-axis for the laser beam which propagated in the z direction. In the phase distribution measurement, the measured wavefront radius curvatures and the theoretically calculated Gaussian beam values had a slight difference. The calculated wavefront radius curvatures at the laser diode facet were 11921.51 £gm and 3.48 £gm in horizontal axis and vertical axis respectively. They were 1809 times and 1.2 times of the measured values. The aperture of taper fiber was expanded because of the energy of laser beams, which also caused the spatial resolution degeneration. Moreover, the wavefront radius curvature in horizontal direction was biggish so the measurement framework also limited the ability of the phase distribution measurement. The above points were the reasons to cause the error of the phase distribution measurement. Furthermore, the measurement of the laser diode facet is under investigation.

Thesis (M.S.)--Rochester Institute of Technology, 1995. / Typescript. Bibliography: leaves 107-114.

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There is continued interest in nonlinear devices for different types of optical signal processing, such as Raman or parametric amplifiers. The small nonlinearity of conventional single-mode fibers sets a major limitation for these devices. A large nonlinearity can be achieved by having a large nonlinear coefficient, a small effective area, or both. Having a small effective area, however, requires efficient coupling to very small core fibers. A novel technique for splicing conventional single-mode fibers to small core fibers is proposed and demonstrated. The coupling efficiency obtained by this technique is considerably improved over that obtained by the butt-joint splice. This technique uses a highly tapered splice in which the field leaves the core and propagates as a fundamental cladding mode before it couples back to the core mode of the small core fiber. At the beginning of the taper the fundamental core mode carries most of the power. Over the down-taper region, the core mode couples to the fundamental cladding mode for which the cladding-air interface plays a major role in guiding the light. Over the up-taper region, the cladding mode is coupled back to the core mode. Fabrication of such a device involves many constraints. Alignment of the cores, the slope of the taper, and the taper length are important issues to ensure that excessive radiation loss does not take place. The theory of tapered single-mode fiber is discussed including adiabaticity criteria, length considerations, mode coupling and wavelength dependence. We use a computational simulation to examine how the field changes from one part of the taper to the other. Variations of the fiber and the field properties along the taper are studied. In this simulation, the tapered region is approximated as a sufficiently large number of cascaded uniform fiber segments of decreasing or increasing diameters. Another analysis based on the conservation of power flow is also provided. Tapered splices were fabricated using two different experimental setups. The experimental setup to verify our theoretical results is shown. The tapering process is thoroughly discussed. The spectrum of a tunable laser passing through a splice shows how modes interact with each other during the tapering process. We successfully fabricated very low loss tapers with extremely small diameters. Tapered splices showed a lower loss than their butt-joint counterparts. Experimental measurements of these tapered splices are presented and discussed. / Ph. D.

Structure evolution of silica aerogel was studied in microwave- and conventionally processed samples over the temperature range from 25 to 1200â °C. The samples were produced using sol-gel processing and dried under carbon dioxide supercritical conditions. After drying, the monolithic samples received a thermal treatment at different programmed temperatures in two different ovens, conventional and microwave. The microwave process was performed using a single mode microwave oven at 2.45GHz. Dielectric properties were measured using the cavity perturbation method, and structural characterization was carried out using a variety of techniques, including absorption surface analysis, Helium pycnometry, Archimedes principle, Fourier transform infrared spectroscopy, X-ray diffraction, and high resolution microscopy. The data obtained revealed that structural differences do exist between microwave- and conventionally processed samples. Three different regions were identified from the structural characterization of the samples. Regions I exhibited a structure densification at temperatures between 25 and 850â °C. Region II was characterized by a bulk densification in the temperature range from 850 to 1200â °C. Region III was represented by the onset of crystallization above 1200â °C. Explanation and possible causes behind the structural differences observed in each region are provided. In general, the structure evolution observed in microwave- and conventionally processed samples followed the same order, but occurred at lower temperature for the microwave process. / Ph. D.

The objective of this thesis is to integrate the optical waveguide and single mode fiber in a passive alignment way on a silicon bench. This technique can reduce the complexity of packaging the individual components and increase yield of the module in order to achieve the goal of the mass production. In this module, buried waveguide structure was used for light guidance. A 1.31µm semiconductor laser was used as the input light source. Light signal launched by semiconductor laser is transferred through the buried waveguide into the single mode fiber. This module structure is consisted of two major parts, namely, the buried waveguide and the silicon bench. Buried optical Waveguide uses SO2 as the bottom cladding. Conventional photolithography procedures and etching technique were used to form a trench on the SiO2 cladding. The waveguide core was fabricated by coating the organic-inorganic hybrid materials into the trench. Finally, an organic-inorganic hybrid materials with a refractive index smaller than that of the core is used as the top cladding. The silicon benches were obtained by etching V-groove and saw-cutting U-groove on the silicon substrates for fixing the fiber. The patterning of buried waveguide and silicon V-groove were fabricated by a single optical mask procedure. Therefore accurate alignment between the waveguide and the single mode fiber can be obtained.

High-power, single-frequency, narrow-linewidth lasers emitting at tailored wavelength are desired for many applications, especially for precision spectroscopy. By way of a free-space resonator, optically pumped semiconductor lasers (OPSLs), a.k.a. vertical external-cavity surface-emitting lasers (VECSELs), can provide near diffraction-limited, high-quality Gaussian beams and are scalable in output power. Free space resonators also allow the insertion of the birefringent filter and the etalon to enforce single-frequency operation. In addition, the emission wavelengths of OPSLs are tailorable through bandgap engineering. These advantages above make OPSL a strong candidate of laser sources for spectroscopic applications including atomic spectroscopy as well as optical lattice clocks. In this research, a single-frequency laser source with high power is demonstrated by applying the injection-locking technique on OPSLs for the first time. The behaviors of the injection-locked OPSL are studied by varying parameters such as output coupling, injection wavelengths and injection power. It was found that the best injection wavelength is by approximately 2 nm shorter than the free-running slave laser at any given pump power. Below the lasing threshold for free-running operation, the laser starts the stimulated emission process as soon as it is pumped, working as a resonant amplifier. With proper parameters, the output power of the injection-locked laser exceeds the output power of its free-running condition. Over 9 W of single-frequency output power at 1015 nm is achieved. The output beam is near-diffraction-limited with Mₓ² = 1.04 and My² = 1.02. By analyzing the surface photoluminescence (PL) and the output performance of the laser, the saturation intensity of OPSLs is estimated to be 100 kW/cm² when the passive loss of 1.4% is assumed. The injection-locked system adds fairly low phase noise to that of the master laser. By measuring the beat note between the master laser and the injection-locked laser, the RMS values of the phase noise are 0.112 rad and 0.081 rad when using the T = 3% and T = 4% output couplers respectively.