No description available.

Steady increases in the bandwidth requirements of access networks and local area networks have created a need for short-reach links supporting data rates of 10 Gb/s and larger. Server applications and data center applications too require such links. The primary challenge for these links lies in the reduction of the cost while retaining or improving the performance. Traditionally, multimode fiber (MMF) has satisfied these needs because of its low installation cost resulting from the alignment tolerance associated with the large core size. However, in view of the ever-increasing performance requirements, extraction of the best performance requires a holistic view of the channel that involves global optimization of transmitter, fiber, receiver performance and signaling strategies. The optimization results in a channel impairment mitigation technique that is a combination of optical, opto-electronic, and electronic methods. Both glass and plastic MMF links have been addressed in this work and many of the advances apply equally to both media. One example that applies strictly to glass MMF is the use of Raman amplification to not only combat attenuation but to reduce intersymbol interference (ISI). Raman amplification was demonstrated as an optical channel impairment mitigation technique enabling multi-km, multi-Gb/s transmission over glass-MMF. We demonstrated both numerically and experimentally that a power penalty reduction of 1.4 dBo can be achieved for 10 Gb/s transmission over 9 km of 62 micron glass MMF with a Raman pump power 250 mW. In recent years, plastic optical fiber (POF) has emerged as a potentially lower cost alternative to glass-MMF in enabling high performance links. The primary objective of this research is to explore the possibilities and develop low-cost, short-reach, high-data-rate POF-links. Using a comprehensive multimode fiber model, we showed that strong mode coupling, together with a reasonably accurate refractive index profile enables 40 Gb/s transmission over 200 m of graded-index POF. We experimentally demonstrated 40 Gb/s error-free transmission over 100 m of graded index perfluorinated POF (GI-PF-POF). We also demonstrated that even larger core (120 micron) GI-PF-POF can support >10 Gb/s over 100 m length. We numerically computed and experimentally measured the differential modal delay of GI-PF-POF to demonstrate that the available bandwidth is nearly independent of the launch conditions. Therefore, the alignment tolerance at the transmitter is increased resulting in a dramatically reduced packaging cost at the transmitter. However, the large-core POF increases the difficultly in capturing of the light efficiently onto a detector and results in optical power penalty and associated modal noise. To solve this, we have designed and developed a 10 Gb/s photoreceiver consisting of a large (100 micron diameter) GaAs PIN photodetector and a regulated cascade input based transimpedance amplifier (TIA) with low input impedance. Thus, a low-cost, alignment-tolerant, high-data-rate link is realized that uses a high-power, high-speed vertical cavity surface emitting laser (VCSEL) transmitter, large-core, high-speed GI-PF-POF, and the developed receiver.

Optical fiber technology continues to advance rapidly as a result of the increasing demands on communication systems and the expanding use of fiber-based sensing. New optical fiber types and fiber-based communications components are required to permit higher data rates, an increased number of channels, and more flexible installation requirements. Fiber-based sensors are continually being developed for a broad range of sensing applications, including environmental, medical, structural, industrial, and military. As optical fibers and fiber-based devices continue to advance, the need to understand their fundamental physical properties increases. The residual-stress distribution (RSD) and the refractive-index distribution (RID) play fundamental roles in the operation and performance of optical fibers. Custom RIDs are used to tailor the transmission properties of fibers used for long-distance transmission and to enable fiber-based devices such as long-period fiber gratings (LPFGs). The introduction and modification of RSDs enable specialty fibers, such as polarization-maintaining fiber, and contribute to the operation of fiber-based devices. Furthermore, the RSD and the RID are inherently linked through the photoelastic effect. Therefore, both the RSD and the RID need to be characterized because these fundamental properties are coupled and affect the fabrication, operation, and performance of fibers and fiber-based devices. To characterize effectively the physical properties of optical fibers, the RSD and the RID must be measured without perturbing or destroying the optical fiber. Furthermore, the techniques used must not be limited in detecting small variations and asymmetries in all directions through the fiber. Finally, the RSD and the RID must be characterized concurrently without moving the fiber to enable the analysis of the relationship between the RSD and the RID. Although many techniques exist for characterizing the residual stress and the refractive index in optical fibers, there is no existing methodology that meets all of these requirements. Therefore, the primary objective of the research presented in this thesis was to provide a methodology that is capable of characterizing concurrently the three-dimensional RSD and RID in optical fibers and fiber-based devices. This research represents a detailed study of the requirements for characterizing optical fibers and how these requirements are met through appropriate data analysis and experimental apparatus design and implementation. To validate the developed methodology, the secondary objective of this research was to characterize both unperturbed and modified optical fibers. The RSD and the RID were measured in a standard telecommunications-grade optical fiber, Corning SMF-28. The effects of cleaving this fiber were also analyzed and the longitudinal variations that result from cleaving were explored for the first time. The fabrication of carbon-dioxide-laser-induced LPFGs was also examined. These devices provide many of the functionalities required for fiber-based communications components as well as fiber-based sensors, and they offer relaxed fabrication requirements when compared to LPFGs fabricated by other methods. The developed methodology was used to perform the first measurements of the changes that occur in the RSD and the RID during LPFG fabrication. The analysis of these measurements ties together many of the existing theories of carbon-dioxide-laser-induced LPFG fabrication to present a more coherent understanding of the processes that occur. In addition, new evidence provides detailed information on the functional form of the RSD and the RID in LPFGs. This information is crucial for the modeling of LPFG behavior, for the design of LPFGs for specific applications, for the tailoring of fabrication parameters to meet design requirements, and for understanding the limitations of LPFG fabrication in commercial optical fibers. Future areas of research concerning the improvement of the developed methodology, the need to characterize other fibers and fiber-based devices, and the characterization of carbon-dioxide-laser-induced LPFGs are identified and discussed.

The ever-increasing data traffic demand drives the evolution of telecommunication networks, including the last-mile access networks as well as the long-haul backbone networks. This Ph.D. dissertation focuses on system design and signal processing techniques for next-generation converged optical-wireless access systems and the high-speed long-haul coherent optical communication systems. The convergence of high-speed millimeter-wave wireless communications and high-capacity fiber-optic backhaul networks provides tremendous potential to meet the capacity requirements of future access networks. In this work, a cloud-radio-over-fiber access architecture is proposed. The proposed architecture enables a large-scale small-cell system to be deployed in a cost-effective, power-efficient, and flexible way. Based on the proposed architecture, a multi-service reconfigurable small-cell backhaul network is developed and demonstrated experimentally. Additionally, the combination of high-speed millimeter-wave radio and fiber-optic backhaul is investigated. Several novel methods that enable high-spectral-efficient vector signal transmission in millimeter-wave radio-over-fiber systems are proposed and demonstrated through both theoretical analysis and experimental verification. For long-haul core networks, ultra-high-speed optical communication systems which can support 1Terabit/s per channel transmission will soon be required to meet the increasing capacity demand in the core networks. Grouping a number of tightly spaced optical subcarriers to form a terabit superchannel has been considered as a promising solution to increases channel capacity while minimizing the need for high-level modulation formats and high baud rate. Conventionally, precise spectral control at transmitter side is required to avoid strong inter-channel interference (ICI) at tight channel spacing. In this work, a novel receiver-side approach based on “super receiver” architecture is proposed and demonstrated. By jointly detecting and demodulating multiple channels simultaneously, the penalties associated with the limitations of generating ideal spectra can be mitigated. Several joint DSP algorithms are developed for linear ICI cancellation and joint carrier-phase recovery. Performance analysis under different system configurations is conducted to demonstrate the feasibility and robustness of the proposed joint DSP algorithms, and improved system performance is observed with both experimental and simulation data.

No description available.

This thesis reports original work on suppression of transient gain excursions in an erbium-doped fibre amplifier (EDFA). The work presented in this thesis is a detailed investigation of four closed-loop systems that control the EDFA gain dynamically. The performance of the four closed-loop systems is evaluated by analytical work, supplemented by computer simulations and insystem measurements performed on a hardware EDFA. In addition, a stability analysis of the four closed-loop systems is presented. In the stability analysis presented in this thesis, nonlinear nature of the four closed-loop systems is taken into consideration. In the stability analysis, in addition to proving that the four closed-loop systems considered are stable, it is proven that for any practical values of the EDFA gain at the initial time of observation, the EDFA gain is restored to the desired value in steady state. These outcomes of the stability analysis are supported by simulation results and experimental results. Errors in system modelling, change in the operating point of the nonlinear closed-loop system, and measurement noise are important aspects of practical implementations of systems that control the EDFA gain dynamically. A detailed analysis of the effects these practical aspects have on the performance of the four closed-loop systems considered is presented. The analysis is validated using computer simulations and experimental measurements. In most of the work reported in the literature on controlling the EDFA gain, controllers that include feedforward and/or feedback components are employed. In the traditional approaches to combining the feedforward and the feedback components, large transient excursions of the EDFA gain can still occur due to errors in the control provided by the feedforward component. In this thesis, a novel approach to combining the feedforward and the feedback components of the controller is presented. Based on the analytical work, the computer simulations and the experimental work presented in this thesis, the novel approach provides a significant reduction in the excursions of the EDFA gain in the transient period.

Thesis (Ph.D.)--University of Western Australia, 2007.

Thesis (M.S.)--University of Texas at El Paso, 2009. / Title from title screen. Vita. CD-ROM. Includes bibliographical references. Also available online.

Random hole optical fibers (RHOF) offer advantages over other types of microstructured optical fibers (MOFs). They are inexpensive and easy-to-make when compared to the high cost of ordered hole MOFs. They also have unique characteristics since they contain open and closed holes. The open holes contain ambient air under normal conditions and the closed holes contain residual gases from the fabrication process at certain pressure. The objective of this research work was to investigate the radiation resistance of Random Hole Optical Fibers (RHOF) for possible use as both sensing element and data transmission medium in nuclear reactor instrumentation and control applications. This work is motivated by the demand for efficient, cost effective, and safe operation of nuclear power plants, which accounts for more than 14% of the world's electricity production. This work has studied the effect of gamma irradiation on RHOF fibers by comparing their performance to that of standard solid telecommunication fibers and commercially available specialty solid fiber designed to be radiations hardened fiber. The fibers were evaluated at different absorbed dose levels: 12 mGy(Si), 350 mGy(Si), and 7200 Gy(Si) by measuring their radiation induced absorption (RIA) on-line. In the low dose test, the maximum RIA measured in untreated RHOF was approximately 8 dB while the RIA in the untreated MMF fibers reached a maximum at about 28 dB. In the high dose test, the maximum RIA measured in untreated RHOF was 36 dB while RIA in the methanol washed RHOF was only 9 dB. RHOF also demonstrated superior radiation damage recovery time over all of the other fibers tested. Based on the experimental evaluations, it was deduced that RHOFs used in this work are resistant to gamma radiation. and recover from radiation damage at a faster rate compared to other fibers tested. The radiation induced absorption (RIA) at the 1550 nm window in the RHOF fibers could be attributed to the OH absorption band tail. However, the existence of other mechanisms responsible for RIA is also postulated. Some of these mechanisms include bulk and surface defects which are related to the fabrication process and the influence of the gases confined within the RHOF microstructure. Gamma radiation resistance of RHOFs can be attributed to the lack of dopants and also possibly the inherent OH and nitrogen content. The behavior of thermally annealed RHOF and their fast recovery is in favor of this hypothesis. / Master of Science

International Telemetering Conference Proceedings / October 26-29, 1992 / Town and Country Hotel and Convention Center, San Diego, California / In this paper, we investigate high-capacity fiber-optic networks for real-time telemetry applications. The network topologies and related network components are analyzed for telemetry fiber-optic Local Area Network (LAN) and Metropolitan Area Network (MAN) as well as MAN internetworking with LANs. Two types of multiplexing techniques, namely, Wavelength Division Multiplexing and Time Division Multiplexing, are proposed to support real-time high-capacity telemetry applications, and the perspective of such networks is also considered. Finally, the optical modulation technique and the choice of optical devices are discussed, which are based on improving the reliability of fiber-optic LANs and MANs.