Amplitude and Phase Shift Keying (APSK) format is one of the most attractive advanced modulation formats because of its good spectral efficiency. As the information bandwidth of the current optical fiber communication system is limited by the optical amplifier bandwidth, it is important to utilize the limited bandwidth effectively. This master thesis focuses on to study the transmission performance of the APSK format both theoretically and experimentally. At first, a theoretical study was conducted using a numerical simulation. As the Extinction Ratio (ER) of the Amplitude Shift Keying (ASK) signal affects the performances of both the ASK and the Phase Shift Keying (PSK) signals, the effect of the ER upon the transmission performance of the APSK format was studied. A clear trade-off between the performance of the ASK signal and the PSK signal due to the change of the ER was observed. Then, in order to improve the performance of the APSK format, a method to improve the transmission performance was proposed. This method was named as ¡§zero-nulling method¡¨, and it solved the trade-off issue caused by the ER. The effectiveness of this method was confirmed through the numerical simulation. Next, an experimental study was conducted. An experimental setup including 330km optical fiber transmission line was prepared, and it was used to confirm the results of the theoretical simulation. The performance trade-off between the ASK and the PSK signals due to the ER was confirmed experimentally. Finally, another experimental study was conducted. An experimental setup of 500km transmission line was used for this study. By adopting the recirculating loop experimental setup, the transmission length could be extended to a few thousand kilometers. The applicability of the ¡§zero-nulling method¡¨ was confirmed using this experimental setup.

In the past, radio-frequency signals were commonly used for low-speed wireless electronic systems, and optical signals were used for multi-gigabit wired communication systems. However, as the emergence of new millimeter-wave technology introduces multi-gigabit transmission over a wireless radio-frequency channel, the borderline between radio-frequency and optical systems becomes blurred. As a result, there come ample opportunities to design and develop next-generation broadband systems to combine the advantages of these two technologies to overcome inherent limitations of various broadband end-to-end interconnect systems in signal generation, recovery, synchronization, and so on. For the transmission distances of a few centimeters to thousands of kilometers, the convergence of radio-frequency electronics and optics to build radio-over-fiber systems ushers in a new era of research for the upcoming very-high-throughput broadband services. Radio-over-fiber systems are believed to be the most promising solution to the backhaul transmission of the millimeter-wave wireless access networks, especially for the license-free, very-high-throughput 60-GHz band. Adopting radio-over-fiber systems in access or in-building networks can greatly extend the 60-GHz signal reach by using ultra-low loss optical fibers. However, such high frequency is difficult to generate in a straightforward way. In this dissertation, the novel techniques of homodyne and heterodyne optical-carrier suppressions for radio-over-fiber systems are investigated and various system architectures are designed to overcome these limitations of 60-GHz wireless access networks, bringing the popularization of multi-gigabit wireless networks to become closer to the reality. In addition to the advantages for the access networks, extremely high spectral efficiency, which is the most important parameter for long-haul networks, can be achieved by radio-over-fiber signal generation. As a result, the transmission performance of spectrally efficient radio-over-fiber signaling, including orthogonal frequency division multiplexing and orthogonal wavelength division multiplexing, is broadly and deeply investigated. On the other hand, radio-over-fiber is also used for the frequency synchronization that can resolve the performance limitation of wireless interconnect systems. A novel wireless interconnects assisted by radio-over-fiber subsystems is proposed in this dissertation. In conclusion, multiple advantageous facets of radio-over-fiber systems can be found in various levels of end-to-end interconnect systems. The rapid development of radio-over-fiber systems will quickly change the conventional appearance of modern communications.

Thesis (M.S.)--Brigham Young University. Dept. of Mechanical Engineering, 2003. / Includes bibliographical references (p. 87-89).

Thesis (M.S.)--Mississippi State University. Department of Chemistry. / Title from title screen. Includes bibliographical references.

Not available / text

In this work, two optical devices, organic photovoltaics (OPVs) and optical fibers, are introduced. Each of these devices have performance drawbacks. The major drawbacks of organic photovoltaics is their low absorption rate due to bandgap mismatch with the solar spectrum as well as poor charge carrier mobility and short exciton diffusion length. In order to overcome some of these drawbacks and increase the efficiency of OPVs, we use plasmonic gold nanoparticles (AuNPs). We report 30% increase in the efficiency of bulk-heterojunction OPV after incorporation of 50 nm AuNPs. The optical, electrical, and thermal impacts of AuNPs on the performance of PVs have been investigated experimentally and using Lumerical Solutions and COMSOL Multiphysics® simulation packages. The major contributions of AuNPs is causing near field enhancement and increasing the absorption of the structure by 65%, decreasing the extracted carrier density by quenching the excitons, changing the workfunction of the structure, as well as increasing the temperature of their surrounded medium when exited at their plasmon resonance frequency. Furthermore, one of the challenges in devices made from optical fibers such as wavelength division multiplexing systems, is self-phase modulation (SPM) which is a nonlinear phenomenon. We introduce a novel method to remove the SPM in liquid core optical fibers (LCOF) using nonlinear organic chromophores with a negative third-order susceptibility. The idea of this work is to eliminate the effective nonlinear refractive index that the optical pulses are experiencing while propagating through the LCOF. Further, a novel method is introduced to characterize the third-order optical nonlinear susceptibility of organic chromophores in LCOF system. The presented method is simple, and can be extended to the characterization of other nanoscale particles such as quantum dots and plasmonic metal nanoparticles in solutions. Finally, a convenient method is presented that enables researchers to investigate the mechanisms behind photobleaching of various materials. The photostability of materials is of great importance for their acceptance in commercial systems such as organic photovoltaics, electro-optic (EO) modulators and switches, etc. This method is based on the simultaneous detection of different signals such as second-, and third-harmonic generations as well as two-, and three-photon excitation fluorescence using multi-photon microscopy.

This thesis examines polarization and polarization mode dispersion (PMD) dynamics in optical fibers as well as the evaluation of probability density functions and bit error rates in a realistic wavelength division multiplexed (WDM) optical communication systems. In the first part of the thesis, experimental studies of the dynamics of polarization in a dispersion compensation module (DCM) are performed in which mechanical shocks are imparted to several different DCMs by dropping a steel ball on the outer casing at different locations and from different heights and the resulting rapid polarization fluctuations are measured. We provide a theoretical model that accounts for the dynamic birefringence generated due to the impact. Next, an experimental technique is proposed to detect the location of temporal polarization activity in WDM systems. It is demonstrated theoretically and in simulations that measurement of both the PMD vector and the Stokes parameters at the WDM frequencies enables the detection of the location of such activity. Different linear prediction procedures are applied to the differential group delay of an optical fiber link assumed to obey the hinge model. The hinges are modeled as polarization rotators with fixed rotation axes and sinusoidally varying rotation angles. Three prediction methods are investigated and consequently compared: an autoregressive model (AR) with Kalman filter, a pattern imitation method and a Taylor expansion technique. The effect of measurement noise on the prediction horizon is also investigated for each prediction method. Using a physically reasonable stochastic model for the hinges, we derive analytical expressions for the temporal autocorrelation functions of the state of polarization (SOP) and the PMD vector. The obtained analytical results are compared to simulations. Finally, we apply the multicanonical method to the probability density function of received symbols and the symbol error ratio (SER) in a dual polarization quadrature phase shift keyed (DP-QPSK) WDM system. We simulate five co propagating channels at a symbol rate of 10.7 GBaud/s and account for PMD and nonlinear effects. We evaluate the performance of the system for two different cases: single mode fibers with full dispersion compensation at the end of the link, effective large area fibers (LEAF) with full dispersion compensation at the end of the link.

<p>All-optical devices have attracted many research interests due to their ultimately low heat dissipation compared to conventional devices based on electric-optical conversion. With recent advances in nonlinear optics, it is now possible to design the optical properties of a medium via all-optical nonlinear effects in a table-top device or even on a chip.</p><p>In this thesis, I realize all-optical control of the optical group velocity using the nonlinear process of stimulated Brillouin scattering (SBS) in optical fibers. The SBS-based techniques generally require very low pump power and offer a wide transparent window and a large tunable range. Moreover, my invention of the arbitrary SBS resonance tailoring technique enables engineering of the optical properties to optimize desired function performance,</p><p>which has made the SBS techniques particularly widely adapted for</p><p>various applications.</p><p>I demonstrate theoretically and experimentally how the all-optical</p><p>control of group velocity is achieved using SBS in optical fibers.</p><p>Particularly, I demonstrate that the frequency dependence of the</p><p>wavevector experienced by the signal beam can be tailored using</p><p>multi-line and broadband pump beams in the SBS process. Based on the theoretical framework, I engineer the spectral profile</p><p> to achieve two different application goals: a uniform low group velocity (slow light) within a broadband spectrum, and a group velocity with a linear dependence on the frequency detuning (group velocity dispersion or GVD).</p><p>In the broadband SBS slow light experiment, I develop a novel noise current modulation method that arbitrarily tailors the spectrum of a diode laser. Applying this method, I obtain a 5-GHz broadband SBS gain with optimized flat-topped profile, in comparison to the ~40 MHz natural linewidth of the SBS resonance. Based on the broadband SBS resonance, I build a 5-GHz optical buffer and use this optical buffer to delay a return-to-zero data sequence of rate 2.5 GHz (pulse width 200 ps). The fast noise modulation method significantly stabilizes the SBS gain and improves the signal fidelity. I obtain a tunable delay up to one pulse-width with a peak signal-to-noise ratio of 7. I also find that SBS slow light performance can be improved by avoiding competing nonlinear effects. A gain-bandwidth product of 344 dB.GHz is obtained in our system with a highly-nonlinear optical fiber.</p><p>Besides the slow light applications, I realize that group velocity dispersion is also optically controlled via the SBS process. In the very recent GVD experiment, I use a dual-line SBS resonance and obtain a tunable GVD parameter of 7.5 ns$^2$/m, which is 10$^9$ times larger than the value found in a single-mode fiber. The large GVD system is used to disperse an optical pulse with a pulse width of 28 ns, which is beyond the capability for current dispersion techniques working in the picosecond and sub picosecond region. The SBS-based all-optical control of GVD is also widely tunable and can</p><p>be applied to any wavelength within the transparent window of the</p><p>optical fiber. I expect many future extensions following this work</p><p>on the SBS-based all-optical GVD control using the readily developed SBS tailoring techniques.</p><p>Finally, I extend the basic theory of backwards SBS to describe the forward SBS observed in a highly nonlinear fiber, where asymmetric forward SBS resonances are observed at the gigahertz range. An especially large gain coefficient of 34.7 W$^{-1}$ is observed at the resonance frequency of 933.8 MHz. This is due to good overlap between the optical wave and the high order guided radial acoustic wave. The interplay from the competing process known as the Kerr effect is also accounted for in the theory.</p> / Dissertation

Thesis (M.Eng.)--University of Wollongong, 2006. / Typescript. Includes bibliographical references: leaf 101-106.

Thesis (M.S.) -- Mississippi State University. Department of Physics and Astronomy. / Title from title screen. Includes bibliographical references.