This thesis presents the fabrication of a low loss hybrid waveguide electric field(E-field) sensor based on optical D-fiber. This novel E-field sensor is formed as part of a contiguous fiber resulting in a flexible and small cross-section device that can be embedded into electronic circuitry. The in-fiber nature of this sensor also eliminates the need for alignment and packaging that conventional sensors need. An optical fiber can detect electric fields when the core of the fiber is partially removed and replaced with an electro-optic polymer. This polymer causes a change in the index of refraction in the waveguide of the device when in the presence of an electric field. The change in the effective index of refraction changes the speed of the light in the vertical axis relative to the light in the horizontal axis creating a phase change between the two axes. This phase change can be detected as a change in the polarity of the light coming out of the fiber. The sensor is formed by partially etching out the core of a D-shaped optical fiber and depositing a polymer to form a hybrid waveguide. The polymer becomes sensitive to electric fields through corona poling. The typical corona poling process is not amenable to poling a polymer located in the fiber core. A method of poling conducive to an in-fiber device was developed and demonstrated. Using PMMA and DR1 for proof of concept, the operation of the first in-fiber hybrid waveguide electric field sensor is demonstrated. Etch depth, polymer composition, and polymer spin rate are optimized to provide strong interaction between the light and the sensing portion of the hybrid waveguide while maintaining low optical loss. High frequency testing was demonstrated to show that the effect is electro-optic. AC testing also allows the Epi of the sensors to be determined at lower electric fields than are required for DC testing, eliminating charge build up and electric field break down issues.

The quadrotor helicopter is a unique flying vehicle which uses the thrust from four motors to provide hover flight capability. The uncoupled nature of the longitudinal and lateral axes and its ability to support large payloads with respect to its size make it an attractive vehicle for autonomous vehicle research. In this thesis, the quadrotor is modeled based on first principles and a proportional-derivative control method is applied for attitude stabilization and position control. A unique means of using an optic flow sensor for velocity and position estimation in an indoor setting is presented with flight results. Reliable hover flight and hallway following capabilities are exhibited in GPS-denied indoor flight using only onboard sensors. Attitude angles can be reliably estimated in the short run by integrating the angular rates from MEMS gyros, but noise on the signal leads to drift which renders the measurement unsuitable to attitude estimation. Typical methods of providing vector attitude corrections such as accelerometers and magnetometers have inherent weaknesses on hovering vehicles. Thus, an additional vector measurement is necessary to correct attitude readings for long-term flights. Two methods of using image processing to determine vanishing points in a hallway are demonstrated. The more promising of the two uses a Hough transform to detect lines in the image and forms a histogram of the intersections to detect likely vanishing point candidates. Once the vanishing point is detected, it acts as a vector measurement to correct attitude estimates on the quadrotor vehicle. Results using onboard vision to estimate heading are demonstrated on a test stand. Together, these capabilities improve the utility of the quadrotor platform for flight without the need of any external sensing capability.

This dissertation explores techniques for improving slab-coupled optical fiber sensor (SCOS) technology for use in specific applications and sensing configurations. SCOS are advantageous for their small size and all-dielectric composition which permit non-intrusive measurement of electric fields within compact environments; however, their small size also limits their sensitivity. This work performs a thorough analysis of the factors contributing to the performance of SCOS and demonstrates methods which improve SCOS, while maintaining its small dimensions and high level of directional sensitivity. These improvements include increasing the sensitivity by 9x, improving the frequency response to include sub 300 kHz frequencies, and developing a method to tune the resonances. The analysis shows that the best material for the slab waveguide is an electro-optic polymer because of its low RF permittivity combined with high electro-optic coefficient. Additional improvements are based on changing the crystal orientation to a transverse configuration, which enhances the sensitivity due to a combined increase in the effective electro-optic coefficient and electric field penetration into the slab. The transverse SCOS configuration not only improves the overall sensitivity but increases the directional sensitivity of the SCOS. Lithium niobate and electro-optic polymer are both experimentally shown to exhibit minimal frequency dependent sensitivity making them suitable for broad frequency applications. Simultaneous interrogation of multiple SCOS with a single tunable laser is achieved by tuning the resonant wavelengths of KTP SCOS so their resonances overlap.

The recent increased availability of additional wavelengths in the telecommunications window of about 1300-1600 nm has generated an interest in new optical materials and devices that can operate outside the normally used regions of 840 nm, 1310 nm, and 1550 nm. Specifically, methods to amplify fiber optical data transmission in the regions where there is limited or no existing methods to achieve amplification is of interest in the chemistry and photonic communities. Raman gain is one method that has been proposed to passively amplify optical data transmission through a distributed process. Amplification is obtained through a nonlinear light scattering process where an optical wave is amplified at the expense of a higher frequency pump wave. Multiple wavelengths can be evenly amplified simultaneously in a desired region by specific selection of one or more pump wavelengths. Herein, the synthesis and characterization of new hybrid inorganic/organic sol-gels and monomers capable of producing broad wavelength Raman scattering over a spectral range of 1200-1670 nm are presented. The synthetic methodology developed facilitates the systematic approach to produce sol-gel derivatives with functional groups known to be strongly Raman scattering. Additionally, a method to synthesize and characterize a large number of different compounds using a combinatorial approach was demonstrated. Thio based derivatives of sulfonyldiphenol, isopropylidenediphenol, and triallyloxy triazine were synthesized in addition to thio derivatives of poly(hydroxystyrene). Micro-Raman spectra of the hybrid sol-gels, thiobased derivatives, and IR spectra of select sol-gel monomers were obtained.

Single-mode fiber transmission can no longer satisfy exponentially growing capacity demand. Space-division multiplexing (SDM) appears to be the only way able to dramatically improve the transmission capacity, for which, novel optical fiber is one of the key technologies. Such fibers must possess the following characteristics: 1) high mode density per cross-sectional area and 2) low crosstalk or low modal differential group delay (DMGD) to reduce complexity of digital signal processing. In this dissertation, we explore the design and characterization of three kinds of fibers for SDM: few-mode fiber (FMF), few-mode multi-core fiber (FM-MCF) and coupled multi-core fiber (CMCF) as well as their applications in transmission and networking. For the ultra-high density need of SDM, we have proposed the FMMCF. It combines advantages of both the FMF and MCF. The challenge is the inter-core crosstalk of the high-order modes. By applying a hole-assisted structure and careful fiber design, the LP11 crosstalk has been suppressed down to -40dB per km. This allows separate transmission on LP01 and LP11 modes without penalty. In fact, a robust SDM transmission up to 200Tb/s has been achieved using this fiber. To overcome distributed modal crosstalk in conjunction with DMGD, supermodes in CMCFs have been proposed. The properties of supermodes were investigated using the coupled-mode theory. The immediate benefits include high mode density and large effective area. In supermode structures, core-to-core coupling is exploited to reduce modal crosstalk or minimize DMGD. In addition, higher-order supermodes have been discovered in CMCFs with few-mode cores. We show that higher-order supermodes in different waveguide array configurations can be strongly affected by angle-dependent couplings, leading to different modal fields. Analytical solutions are provided for linear, rectangular and ring arrays. Higher-order modes have been observed for the first time using S2 imaging method. Finally, we introduce FMF to gigabit-capable passive optical networks (GPON). By replacing the conventional splitter with a photonic lantern, upstream combining loss can be eliminated. Low crosstalk has been achieved by a customized mode-selective photonic lantern carefully coupled to the FMF. We have demonstrated the first few-mode GPON system with error-free performance over 20-km 3-mode transmission using a commercial GPON system carrying live Ethernet traffic. We then scale the 3-mode GPON system to 5-mode, which resulted in a 4dB net gain in power budget in comparison with current commercial single-mode GPON systems.

The need for more bandwidth in communications has stimulated the search for new fiberizable materials with properties superior to fused silica which is the current state-of-the-art. One of the key properties is Raman gain by which a pump beam amplifies a signal beam of longer wavelength. An apparatus capable of directly measuring the spectral dependence and absolute magnitude of the material Raman gain coefficient using nonlinear optics techniques has been built. Using radiation from a 1064 nm Nd:YAG laser as the pump and from a tunable Optical Parametric Generator and Amplifier as the signal, the Raman gain spectrum was measured for different families of glass samples with millimeter thickness. A number of glass families were investigated. Tellurites with added oxides of tungsten, niobium, and thallium produced the largest Raman gain coefficients of any oxide family reported to date, typically 30-50 times higher than that of fused silica. On the other hand, phosphate families were found with spectrally broad Raman gain response, 5 times broader than fused silica and flat to [plus or minus] dB over the full spectral range in some compositions. Although the chalcogenides were found to photodamage easily, coefficients 50 - 80 times that of fused silica were measured. Finally, a numerical study was undertaken to predict the theoretical performance and noise properties of tellurite fibers for communications. Included in the computer modeling were linear loss; the interaction among multiple pumps and signals; forward and/or backward propagating pump beams; forward, backward and double Rayleigh scattering; noise properties of amplifiers; excess noise, etc. This led to a comparison of the optical signal-to-noise characteristics for Raman gain in a tellurite versus a silica fiber.

The main objective of this research is to explore, investigate and develop the new data analysis techniques along with novel sensing technologies for structural health monitoring applications. The study has three main parts. First, a systematic comparative evaluation of some of the most common and promising methods is carried out along with a combined method proposed in this study for mitigating drawbacks of some of the techniques. Secondly, nonparametric methods are evaluated on a real life movable bridge. Finally, a hybrid approach for non-parametric and parametric method is proposed and demonstrated for more in depth understanding of the structural performance. In view of that, it is shown in the literature that four efficient non-parametric algorithms including, Cross Correlation Analysis (CCA), Robust Regression Analysis (RRA), Moving Cross Correlation Analysis (MCCA) and Moving Principal Component Analysis (MPCA) have shown promise with respect to the conducted numerical studies. As a result, these methods are selected for further systematic and comparative evaluation using experimental data. A comprehensive experimental test is designed utilizing Fiber Bragg Grating (FBG) sensors simulating some of the most critical and common damage scenarios on a unique experimental structure in the laboratory. Subsequently the SHM data, that is generated and collected under different damage scenarios, are employed for comparative study of the selected techniques based on critical criteria such as detectability, time to detection, effect of noise, computational time and size of the window. The observations indicate that while MPCA has the best detectability, it does not perform very reliable results in terms of time to detection. As a result, a machine-learning based algorithm is explored that not only reduces the associated delay with MPCA but further iii improves the detectability performance. Accordingly, the MPCA and MCCA are combined to introduce an improved algorithm named MPCA-CCA. The new algorithm is evaluated through both experimental and real-life studies. It is realized that while the methods identified above have failed to detect the simulated damage on a movable bridge, the MPCA-CCA algorithm successfully identified the induced damage. An investigative study for automated data processing method is developed using nonparametric data analysis methods for real-time condition maintenance monitoring of critical mechanical components of a movable bridge. A maintenance condition index is defined for identifying and tracking the critical maintenance issues. The efficiency of the maintenance condition index is then investigated and demonstrated against some of the corresponding maintenance problems that have been visually and independently identified for the bridge. Finally, a hybrid data interpretation framework is designed taking advantage of the benefits of both parametric and non-parametric approaches and mitigating their shortcomings. The proposed approach can then be employed not only to detect the damage but also to assess the identified abnormal behavior. This approach is also employed for optimized sensor number and locations on the structure.

The general organization and 'function of the vertebrate visual system has been under Investigation since the late nineteenth century (Gudden, lS7Qa, Gudden, 1870b). The organization of optic tracts and subcortical optic centers for the majority of vertebrates studied are found to be similar in both structure and function (Gudden, 1870a, Gudden, 1870b, Minkowski, 1913» Minkowski, 1920, and Lashley, 193^a). The sense organ, the eye, contains specific photoreceptor cells designated as either retinal rods or retinal cones. These two types of retinal cells possess an ability to convert light quanta into nerve impulses. The nerve impulses are transmitted via the optic nerves, and optic tracts to four major anatomical areas of Initial synapse within the central nervous system; the lateral geniculate bodies (for both the dorsal and ventral, nucleus) , the stratum optlcum of the superior colliculi, tlie pretectum, and the cuter cellular layers of the visual cortex located on either edge of the calcarine fissure of the temporal lobes (see Figures 1, 2, and 3)-

No description available.

Fiber optic sensors offer the ability to measure different types of physical quantities in more harsh environments, such as temperature, pressure and deformations. Some of these demanding environments include chemicals that affect the sensitivity of the sensor, and therefore its resili-ence deteriorates. This work focuses on using experimental techniques to find a method that protects the optical fiber in these chemically demand-ing environments, by coating the fiber with a polymer layer which has the task of protecting it in such environments. A challenge that comes with coating the fiber optic sensor with a polymer layer is that the ability to obtain information becomes more difficult as, its sensitivity deterio-rates. In this project, a type of polymer called polyimide will be tested, using different concentrations and number of layers coated on the optical sensor to investigate the extent that these factors affect the sensor´s ability to cope in chemically demanding environments and also how the sensi-tivity is affected. Thus, the coating method used was soap film coating (SFC). A spectrometer was used to examine the sensitivity of the sensor (using total internal reflection (TIR) and surface plasmon resonance (SPR)). The examination of the resistance of the optical fiber was meas-ured by immersing the polymer-coated sensor in a corrosive liquid for various time intervals and then examining its protective ability. The re-sults obtained through this work demonstrate that polyimide as a coating material provides a protective effect by improving the resistance. The sen-sitivity was most affected when the concentration of the polyimide layer increased from 1-layer to 2-layer polyimide at high concentrations. Re-sistance also increased as the concentration increased, however, 1-layer and 2-layer protection did not have a major impact. The results of this project can be used to further test different types of polymers, for example PVDF. Even more tests with the same attitude and conditions should be carried out to ensure the conclusions and results, and to estimate the measurement uncertainties in the work.