Fiber optics technology is being used in many applications, both in the military world and in the industrial world. A broad overview of this technology is provided, including a discussion of the fundamentals of fiber operation and component characteristics. Applications of fiber optics in both military and industrial communities is addressed, identifying specific examples in both cases. In addition, market projections and technology trends are discussed for both the military and industrial communities. / Master of Science

The presence of low frequency cutoffs in the forward path of the information signal leads to inter-symbol interference (ISI) and degradation of the signal to noise ratio at the sampling instant in digital on-off keying (OOK) systems. The low frequency cutoffs occur as a result of the presence of power separation filters in a line wire system and gain instability of APD's to D.C. in fiber optic systems. Also, it is easier to design amplifiers that do not extend to D.C. The ISI which manifests itself in the form of baseline wander can cause appreciable degradation in the signal to noise ratio. This thesis investigates two ways of combating the baseline wander problem. They are quantized feedback and line coding schemes. A detailed performance evaluation of quantized feedback scheme is performed. An overview of line coding schemes is given and some specific codes are evaluated in terms of S/N degradation at the receiver. / Master of Science

Interference between the modes of an optical fiber generates specific mode (intensity) patterns which get modulated by disturbances in the optical fiber system. Mode-mode interference has been analyzed from first principles and a model based on differential phase modulation presented. Mode-mode interference effects such as intensity modulation of the mode patterns are directly related to differential phase modulation between modes which arises due to the difference between the propagation constants of the constituent modes. Practical implementation of modal methods involves selective launching of modes and processing of the output pattern to demodulate the information. Axial strain has been chosen as the modulating mechanism in experiments designed to quantify mode-mode interference effects. Quasi-statically varying strain as well as vibrational strain was used to study 'dc' and 'ac' mechanisms. Specific mode combinations have been excited and their radiation patterns identified. Mode pattern changes have been described. Experimental observations and results correlate very well with analysis. / Master of Science

As attenuation in silica based fibers approaches its ultimate theoretical limit, investigation is in progress to develop new materials which exhibit lower losses than silica. These bulk materials could then be used to fabricate ultralow loss optical fibers which operate farther out in the infrared than do silica fibers. Such infrared fibers could be used in long, repeaterless telecommunications links, the transmission of <i>CO</i> and <i>CO</i>₂ laser power, and in several sensing mechanisms. This thesis presents an overview of these new fibers and how they can be applied in noncontact temperature measurement. Fiber optic temperature sensing is thus reviewed, and an optical fiber pyrometer is discussed. / Master of Science

Tunneling through a potential barrier is a well-known concept in quantum mechanics. It is shown that tunneling is not an inherently quantum-mechanical phenomenon but that it occurs in classical optics as well. Single-layer and double-layer dielectrics in which optical tunneling occurs are shown to serve as the basis of optical filters, the double-layer tunnel filter having a much higher resolution capability than the single-layer tunnel filter. Optical amplifiers used as a receiver preamplifier and as linear intermediate repeaters are evaluated. Performance parameters of particular interest are the receiver sensitivity and the total system gain. The effects of optical amplifier gain and bandwidth on those parameters are studied. Finally, the effects of gain variations are considered. It is shown that gain control gives very poor results, whereas power control does not severely limit the system performance, particularly when a small number of amplifiers are used. / Master of Science

This thesis proposes a new media access protocol for local area and metropolitan area all-optical networks employing wavelength division multiplexing (WDM). Through WDM, multiple channels are created on a single fiber, and an aggregate network bandwidth far greater than the peak electronic processing speed can be realized. The new protocol, Dynamic Media Access Control Scheme (DMACS), is based on the Dynamic Interleaved Slotted Aloha (DISA) protocol. It improves on DISA by adding a common control channel that provides reservations for constant bit-rate traffic, acknowledgments, and global flow control. DMACS supports connection setup and tear down, different traffic classes, flow control, and packet resequencing in an attempt to integrate features of the transport layer directly into the media access control layer. The performance of the DMACS protocol has been evaluated through analytical methods and simulation. It was found to be superior to the DISA protocol and to provide good performance that is relatively insensitive to the number of stations and the traffic conditions in the network. / Master of Science

Modal domain analysis has gained special attention over the years due to its immense value both in fiber-optic sensor technology and communication systems. This presentation is aimed at reviewing the research done in that area so far and at describing a data acquisition system that can be used extensively for such analysis. This work primarily concentrates on the capabilities of the PN-2304 OPTOMATION II system in the study of mode coupling and transient distance analysis in graded-index optical fibers, as well as microbending loss measurements and phase modulation effects in a fiber guiding four modes. While the results of these measurements have been useful in themselves, the performance of the data acquisition system has been exploited to a great extent thus rendering a sophisticated tool for modal distribution studies. The system has been found useful in fiberdyne measurements and speckle pattern analysis thus leading to information on the propagating modes. Chapters I and 2 give a brief introduction to fiber optic systems and mode theory while Chapter 3 reviews the work already done in that area. Chapter 4 describes the PN-2304 OPTOMATION II and its capabilities in modal analysis and Chapter 5 reports the various measurements made using the system and their results. / M.S.

The issue of protecting a fiber communication system is of considerable concern mainly because of the fiber's capability of carrying a large amount of traffic. In this study, we are concerned with the role of topology in relation to the survivability and network cost. Studying three simple network topologies, the ring, hub and mesh topologies, the ring topology is found to have many advantages for high capacity communication systems. Combinations of the simple network topologies may be used to combine the advantages of each topology. A toroidal grid topology, which combines advantages of ring and mesh topologies, is described and evaluated. Analytic results shows that the toroidal grid achieves survivability with lower incremental costs compared to the ring topology. The analytical results are limited to simple geometric and uniform traffic models. A computer program is developed to analyze the performance of more realistic networks. The computer results show that the length of a network system is a major factor affecting the cost of the network. The idea of having a multiply interconnected ring system appears to be an attractive topology for long-distance applications. / Master of Science

Recent progress in reducing the extrinsic losses of fluorozirconate optical fibers has increased the material research efforts for these new waveguides. Fluorozirconate fibers, which are inherently more transparent than silica fibers, are predicted to have intrinsic losses as low as 0.001 dB/km at 3.45 μm [11]. Unfortunately, high intrinsic losses still plague these new optical fibers and these losses must be understood before ultra-low loss fibers become a reality. An automated fiber optic characterizer can help determine the loss mechanisms and the optical properties of fluorozirconate fibers so extrinsic loss mechanisms can be understood and eventually controlled. The automated fiber optic characterizer can also speed up the measurement process by using a microcomputer to align the fiber, calculate the results, and plot the graph. This thesis presents the technical issues involved in the design and construction of an automated infrared fiber optic characterizer. The thesis also outlines the test results of a constructed automated fiber optic characterizer. The characterizer measures spectral attenuation between 0.8 μm and 4 μm, differential modal attenuation between 1.6 μm and 4 μm, and numerical aperture at 1.55 μm and 2.55 μm. / Master of Science

The critical heat flux (CHF) point for a reactor core system is one of the most important factors to discuss in regards to reactor safety. If this point is reached, standard coolant systems are not enough to handle the temperature increase in the cladding, and the likelihood of meltdown greatly increases. While the nucleate boiling and film boiling regimes have been well-investigated, the transition boiling regime between the point of departure from nucleate boiling (DNB) and the minimum film boiling temperature (T_min) remains difficult to study. This is due to both the complexity of the phenomena, as well as limitations in measurement, where experiments typically utilize thermocouples for temperature data acquisition. As a result of technological advancement in the field of fiber optics, it is possible to measure the quenching temperature to a much higher degree of precision. Optical fiber sensors are capable of taking many more measurements along a fuel simulator length than thermocouples, which are restricted to discrete points. In this way, optical fibers can act as an almost continuous sensor, calculating data at a resolution of less than one millimeter where a thermocouple would only be able to measure at one point. In this thesis, the results of a series of quenching experiments performed on stainless steel, Monel k500, and Inconel 600 rods at atmospheric pressure, with different subcooling levels and surface roughnesses, will be discussed. The rewetting temperature measurement is performed to compare results between thermocouples and optical fiber sensors in a 30 cm rod. These results are further discussed with regard to future application in two-phase flow experiments. / Master of Science / There are multiple types of boiling that can occur depending on the heat transfer capabilities of the system and the power applied to the coolant. The most common is nucleate boiling, where vapor produced at the surface forms bubbles and move away from the surface due to buoyancy. At a high enough power, the bubbles can coalesce into a film and lead to a point at which the liquid coolant can no longer contact the surface. Since vapor is not as effective at transferring heat from the surface, the temperature will increase drastically. In nuclear reactors, this situation (known as departure from nucleate boiling), can quickly lead to a meltdown of the fuel rods. Another important safety parameter in nuclear reactors is the minimum temperature at which this vapor film can be maintained, T_min. This parameter is a source of significant concern with regard to accident scenarios such as LOCA (loss of coolant accident), where reintroducing coolant to the rods efficiently is of top priority. While much research has been done on nucleate and film boiling, it has been difficult to study the transition period between the two regimes due to both its transient nature and the lack of continuous measurement capabilities. Typically, temperature is measured using thermocouples, which are point-source sensors that do not allow for high spatial resolution over a large area. This thesis deals with the utilization of optical fibers for temperature measurement, which are capable of calculating data at every millimeter, potentially a much more precise measurement system than with the thermocouples. The experiments performed in this paper are quenching experiments, where a rod embedded with thermocouples and an optical fiber is heated to well above T_min and quickly plunged into a volume of water, in order to view the transition from film to nucleate boiling.