Approved for public release, distribution is unlimited / Optical fiber has been the preferred cabling technology for certain building and campus network LAN backbones. Until recently, however, the use of fiber as a cabling medium to the desktop has been confined to special environments that require the unique properties of optical fiber such as noise immunity, security, distance, high bandwidth demands (CAD/CAM, video conferencing), and immunity to electrical interference. However, choosing to use optical fiber in a network over other cabling options may present significant advantages in its inherent ability to handle data at higher speeds. Decreasing costs of optical fiber components compared to the increasing electronic costs of carrying Gigabit Ethernet over Cat 5 or Cat 5E UTP copper cabling has also accelerated the migration to optical fiber LAN. The thesis conducts a feasibility study of implementing a Fiber Optic Local Area Network in Software Metrics Laboratory in Ingersoll 158. / Major, Republic of Singapore Air Force

Despite that the RGC axons closely associated with astrocytes, the role of astrocytes in RGC regeneration was uncertain. In view of this, the effect of cultured adult astrocytes on RGC regeneration through an extensive ON lesion segment was studied. Adult ON astrocytes were prepared by sub-culturing of cells migrating out of ON explants. A small hole in the ON was punctured by 27G needle and about 0.5 to 1.0mul (1000 cells) cultured astrocytes was injected into the extensive ON lesion segment. We found that cultured adult astrocytes promoted significant RGC axon regeneration in the extensive ON lesion. / Finally, co-transplantation of intravitreal PN followed by transplantation of astrocytes into the extensive lesion has a synergistic effect on the regrowth of RGC axons, as indicated by the maximum distance achieved by regenerating axons and integrated intensity of staining of the CTB-labeled axons. Transplanatation of VPN+AST, VPN+NAST and NPN+AST as 3.9, 2.5 and l.9 times more potent in inducing regeneration than that of NPN+NAST as shown by integrated intensity measurement. However, co-transplantation of PN and astrocytes could not enhance RGC survival. (Abstract shortened by UMI.) / In this study, we have established an extensive lesion paradigm to study the behavior of injured retinal ganglion cell (RGC) axons after ON crush in adult golden hamster. We found that RGC axons regenerated in the extensive lesion for 406.8mum at 1 week post-crush to 1174.0mum at 4 weeks post-crush. RGC axons were able to regenerate the entire lesion segment but they terminated precisely at the interface between the lesion and the distal segment of the ON. Regrowing axons were intimately associated with astrocytes which repopulated the lesion segment. Repopulated oligodendrocytes were scattered in the lesion segment and myelin debris was significantly decreased in the lesion segment with time. / It is commonly believed that central nervous system (CNS) neurons are unable to regenerate after injury. Recently, there have been several lines of evidence showing that damaged CNS neurons can undergo axonal regeneration under appropriate conditions. Since the retina and optic nerve (ON) are regarded as part of the CNS, therefore, they are used as a model to study CNS regeneration. / Kong Wai Chi. / "July 2005." / Adviser: Y.P. Cho. / Source: Dissertation Abstracts International, Volume: 67-07, Section: B, page: 3616. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references (p. 96-115). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.

Sensing rotation has been an essential topic in navigation and many other applications. Gyroscopes based on propagation of light beams over fixed distances have gained interest with the development of the laser. Since the 1970s, with the development of fiber optics these laser based gyroscopes have developed into compact devices, which can fit in the palm of your hand. In this thesis, we describe and analyze the development of a fiber-optic gyroscope. Fiber optic gyroscopes (also called fiber gyro or FOG) have been under development for different types of applications for more than 30 years all around the world. The physical basis of the fiber gyro is the Sagnac effect that was discovered in the early 1900s and is named after its discoverer. In this work, we first explain the principle of operation of the Sagnac effect and we derive the fundamental formulations in order to have an analytical understanding of the theory. Then, we examine the fiber optic gyro configuration component by component, starting with the laser diode pumped broadband light emitting Erbium-doped superfluorescent source. In addition, the principle of phase modulation, electro-optic phase modulators, fiber optic cables and fiber winding techniques, such as quadrupolar winding is explained within the context of development of the FOG. v The FOG that was assembled was based on circulation and sensing of broadband light centered around 1550nm. The fiber coil was 5km long in order to increase sensitivity in the FOG device. Since single-mode fibers were used steps were taken to ensure successful operation even with polarization dependent errors. The constructed system demonstrated a low sensitivity with a large uncertainty while sensing typical rotation rates. Reasons behind the errors and low sensitivity, as well as improvements that can be made are discussed.

Silicon is the dominant material in Microelectronics. Building photonic devices out of silicon can leverage the mature processing technologies developed in silicon CMOS. Silicon is also a very good waveguide material. It is highly transparent at 1550nm, and it has very high refractive index of 3.46. High refractive index enables building high index contrast waveguides with dimensions close to the diffraction limit. This provides the opportunity to build highly integrated photonic integrated circuit that can perform multiple functions on the same silicon chip, an optical parallel of the electronic integrated circuit. However, silicon does not have some of the necessary properties to build active optical devices such as lasers and modulators. For Example, silicon is an indirect band gap material that can’t be used to make lasers. The centro-symmetric crystal structure in silicon presents no electro-optic effect. By contrast, electro-optic polymer can be engineered to show very strong electro-optic effect up to 300pm/V. In this research we have demonstrated highly compact and efficient devices that utilize the strong optical confinement ability in silicon and strong electro-optic effect in polymer. We have performed detailed investigations on the optical coupling to a slow light waveguide and developed solutions to improve the coupling efficiency to a slow light photonic crystal waveguides (PCW). These studies have lead to the demonstration of the most hybrid silicon modulator demonstrate to date and a compact chip scale true time delay module that can be implemented in future phased array antenna systems. In the future, people may be able to realize a photonic integrated circuit for optical communication or sensor systems using the devices we developed in our research. / text

[Truncated abstract] Formation and consolidation of the retinotectal projection during optic nerve regeneration has been associated with two major interlinked processes. Initially, retinal ganglion cell (RGC) axons are guided by molecular guidance cues, such as the Eph receptor tyrosine kinases and their ligands, the ephrins, to their approximately correct location and form a coarse topographic map in the optic tecum. Such axon guidance occurs in the absence of neural activity and is considered to be activity-independent. The second process involves glutamatergic excitation, whereby correctly located connections are strengthened by correlated neural activity, whilst removing inappropriately located ones thereby sharpening the topography.The second process is considered to be activitydependent. Here, a number of experiments were undertaken to further examine the interrelationships of activity-dependent and independent processes with respect to functional outcomes. Two models of optic nerve regeneration were studied. In goldfish, following optic nerve crush, regeneration is successful. … In goldfish, guidance along the medio-lateral tectal axis may occur through preordering of axons prior to entering the tectum via the appropriate medial and lateral brachium, with EphA/ephrin-A then guiding axons over the rostral-caudal axis establishing gross topography. The increase in involvement of NMDA-mediated transmission during the period of activity-dependent refinement consolidated the role of this receptor in synapse plasticity. However what triggers NMDA-mediated activity to increase is still largely unresolved, although as the factors governing receptor trafficking during development and synaptic plasticity become better understood, these can be applied to the period of plasticity associated with regenerating axons. And finally, as GABAergic inhibition appears to suppress activity-dependent refinement, means of overcoming this inhibition through 4 such methods as visual training or pharmacological intervention may have significance for mammalian regeneration.

No description available.

Le syndrome d’apnées obstructives du sommeil (SAOS) est associé à la survenue de neuropathies optiques, en particulier la neuropathie optique ischémique antérieure aigue non artéritique (NOIAA-NA). Parmi les mécanismes d’apparition de cette neuropathie et potentiellement associés au SAOS, la dysrégulation et l’inflammation vasculaires pourraient jouer un rôle. Il n’existe aucune donnée dans la littérature sur l’effet de l’hypoxie intermittente (HI) chronique sur la fonction vasculaire de l’œil.Le but de ce travail était de développer des techniques d’évaluation de la fonction vasculaire oculaire chez le rat et de les appliquer à l’étude des conséquences vasculaires oculaires de l’HI. Ainsi, deux approches complémentaires ont été développées : 1) un prototype de fluxmètre laser Doppler (LDF) adapté au rongeur pour l’évaluation in vivo de la perfusion sanguine rétinienne et de la tête du nerf optique (TNO) et 2) le modèle d’étude de l’artère ophtalmique (AO) du rat par myographie vasculaire, in vitro.La mise au point du LDF chez le rat sain a permis de valider la pertinence du signal provenant des artères rétiniennes. A l’inverse, nos données invalident l’intérêt de la mesure au niveau de la TNO. En réponse à l’inhalation d’oxygène pur, nous observons une diminution de 17,0 ± 13,7 % de la vélocité artérielle rétinienne (VelART). Nous n’observons pas de variation significative de VelART lors d’injection intra-carotidienne d’endothéline 1 (ET-1) malgré une forte vasoconstriction des vaisseaux rétiniens. Les perspectives consistent à associer une caméra de haute résolution à un système bidirectionnel de LDF. L’étude de la réactivité de l’AO par myographie chez le rat soumis à 14 jours d’HI a mis en évidence une augmentation de la contraction à l’ET-1, associée à une augmentation de la réponse médiée par les récepteurs de type A (ETRA)et à une surexpression des ETRA au sein de l’AO. La relaxation NO-dépendante était diminuée chez le rat HI, et associée à un effet prédominant des produits vasoconstricteurs du cytochrome P450. Ces réponses étaient associées à une augmentation de la présence d’anions superoxyde dans la paroi de l’AO. Des études complémentaires sont nécessaires pour explorer les mécanismes à l’origine des ces altérations vasculaires, en particulier le rôle du stress oxydant. / Obstructive sleep apnea (OSA) has recently been associated with the occurrence of optic neuropathies, especially acute non-arteritic anterior ischemic optic neuropathy (NAION). Among the mechanisms of NAION onset potentially associated with OSA, vascular dysregulation and inflammation may play a role. There is still no data on the effect of chronic intermittent hypoxia (IH) on vascular function of the eye. The purpose of this work was to develop techniques for assessing rat ocular vascular function and apply them to the study of the ocular vascular consequences of IH. Thus, two complementary models have been developed: 1) a laser Doppler flowmeter (LDF) prototype adapted for rodents, to evaluate in vivo retinal and optic nerve head (ONH) blood perfusion and 2) in vitro model of rat ophthalmic artery (OA) study by myography. Preliminary work on healthy rat enabled us to validate the relevance of retinal arteries LDF signal, but not that of the ONH. Retinal blood velocity (VelART) dropped by 17.0 ± 13.7% in response to pure oxygen inhalation. We did not observe any significant change in VelART signal after intracarotidian endothelin 1 (ET -1) injection, despite strong vasoconstriction of retinal vessels. OA reactivity study by myography in rats exposed to a 14-day IH showed increased contraction to ET-1, associated with an increased endothelin receptor A-mediated (ETRA) response and ETRA overexpression within the AO. NO-dependent relaxation is reduced in IH rats, and associated with a shift towards vasoconstrictive effects of cytochrome P450 products. These responses were associated with an increase in superoxide anions in the OA wall. Further studies are needed to explore the underlying mechanisms of these vascular changes, particularly the role of oxidative stress. Understanding of the LDF signal is partial and should be further explored to permit application to the study of IH rat.

This thesis deals with the aspects of methods for pulsed high-level EM quantities measurement. Methods for current and voltage measurement in pulsed power generator and power measurement in pulse microwave generator are discussed. New approaches to single-shot measurement methods application are proposed. The theoretical analysis of suitable sensor designs is performed. The magneto-optic measurement method has been experimentally realized. On the basis of experimental results a fiber-optic current sensor has been designed and theoretically analyzed. For identification and measurement of the free-space electromagnetic pulse a combined calorimetric sensor has been designed and built.

The purpose of this project is to explore the FBG (Fiber Bragg Grating) technology and create a force sensor. The result can be used as a basis for further projects.The project starts with force and strain measurements. The project then evolves to incorporate multiple FBG sensors. An uncommon method of writing the FBG withcoating is tested, which results in a FBG with most of the coating left.The result is a multi-FBG sensor. And even though the individual FBG is not linear the sum shows fantastic linearity with R-square of 0.99999. The change in wavelength is 1328pm/N. A common issue in the strain measurement is discussed and proof is provided. This shows that the reference value of the FBG is 1.12pm/μstrain instead of 1.21pm/μstrain. This is important if the FBG is mounted in a structure, because then the material proprieties will be dominating. Another result is that the peaks of Fabry Perot grating pair are linear but with different coecients.

No description available.