Thesis (Ph. D.)--School of Physics , Faculty of Science, University of Sydney, 2004. / Bibliography: p. 237-254.

Thesis (M.S.)--Worcester Polytechnic Institute. / Keywords: fiber amplifier; erbium; excited state absorption; rare earth fluorescence; neodymium. Includes bibliographical references (leaves 70-72).

Thesis (Ph. D.)--University of Sydney, 2004. / Title from title screen (viewed 14 May 2008). Submitted in fulfilment of the requirements for the degree of Doctor of Philosophy to the School of Physics, Faculty of Science. Includes bibliographical references. Also available in print form.

Thesis (M.S.)--Ohio University, November, 1990. / Title from PDF t.p.

Thesis (Ph. D.)--Rutgers University, 2008. / "Graduate Program in Mechanical and Aerospace Engineering." Includes bibliographical references (p. 133-137).

Thesis (M. Sc.)--University of Canterbury, 2006. / Typescript (photocopy). Includes bibliographical references (leaves 60-62). Also available via the World Wide Web.

The properties of photo-induced gratings in germania doped glass fibers were studied. Permanent phase gratings in a fiber core were fabricated by the mixing of two contra propagating waves. Experiments are described and results are presented which show that the strength of a photoinduced grating is strongly dependent on the writing power as well as the laser writing wavelength. A rigorous development of linear coupled mode theory for the contra propagation geometry is given and used to model the experimentally observed grating responses as a function of fine tuning frequency of probing light. Measurements have been done of the amplitude and phase response of the grating structure and compared with theoretical models of uniform and chirped gratings. The theoretically predicted negative group velocity dispersion in fiber grating was observed interferometrically and described in detail. The nonlinear coupled mode theory has been fully implemented in a computer program and some numerical results are given in the second part of this thesis. The dynamics of a pulse propagating in the fiber grating is simulated and the results show its dependence on pulse energy, frequency detuning, and the type of grating geometry. A limitation is found in the dispersion property of a constant amplitude fiber grating so that the pulse compression ratio and the width of a compressible pulse is strictly limited to ≅250 picoseconds.

This thesis concerns polarization mode dispersion (PMD) in optical fiber communications. Specifically, we study fiber birefringence, PMD stochastic properties, PMD mitigation and the interaction of fiber birefringence and fiber nonlinearity. Fiber birefringence is the physical origin of polarization mode dispersion. Current models of birefringence in optical fibers assume that the birefringence vector varies randomly either in orientation with a fixed magnitude or simultaneously in both magnitude and direction. These models are applicable only to certain birefringence profiles. For a broader range of birefringence profiles, we propose and investigate four general models in which the stochastically varying amplitude is restricted to a limited range. In addition, mathematical algorithms are introduced for the numerical implementation of these models. To investigate polarization mode dispersion, we first apply these models to single mode fibers. In particular, two existing models and our four more general models are employed for the evolution of optical fiber birefringence with longitudinal distance to analyze, both theoretically and numerically, the behavior of the polarization mode dispersion. We find that while the probability distribution function of the differential group delay (DGD) varies along the fiber length as in existing models, the dependence of the mean DGD on fiber length differs noticeably from earlier predictions. Fiber spinning reduces polarization mode dispersion effects in optical fibers. Since relatively few studies have been performed of the dependence of the reduction factor on the strength of random background birefringence fluctuations, we here apply a general birefringence model to sinusoidal spun fibers. We find that while, as expected, the phase matching condition is not affected by random perturbations, the degree of PMD reduction as well as the probability distribution function of the DGD are both influenced by the random components of the birefringence. Together with other researchers, I have also examined a series of experimentally realizable procedures to compensate for PMD in optical fiber systems. This work demonstrates that a symmetric ordering of compensator elements combined with Taylor and Chebyshev approximations to the transfer matrix for the light polarization in optical fibers can significantly widen the compensation bandwidth. In the last part of the thesis, we applied the Manakov-PMD equation and a general model of fiber birefringence to investigate pulse distortion induced by the interaction of fiber birefringence and fiber nonlinearity. We find that the effect of nonlinearity on the pulse distortion differs markedly with the birefringence profile.

M.Ing. (Electrical and Electronic Engineering) / A distributed temperature fiber sensor based on the ratio of the Raman anti-Stokes to Rayleigh backscattered light components is studied. The aim of the study is to propose a method of quantifying the noise exhibited in the Rayleigh backscattered signal and further propose correlation coding techniques to reduce the noise in the Rayleigh and Raman backscattered signals. The noise in the Rayleigh backscattered signal is referred to as “interferometric noise”. When Rayleigh scattering along the length of an optical fiber occurs, some of the scattered light travels in a direction opposite to the direction of propagation, and is called backscattered light. When the coherence length of the optical source permits interactions between the Rayleigh backscattered light, there is a possibility for the interacting backscattered light, within a distance that is half the coherence length, to interfere with each other. Furthermore, when the sensing optical fiber is greater than the coherence length of the optical source, there will be several interference sections along the length of the sensing fiber causing the intensity of the Rayleigh backscattered light at the photo-detectors to vary randomly. The intensity variation gives the Rayleigh backscattered signal a jagged appearance indicating the presence of interferometric noise. The longer the coherence length of the optical sources, the larger the intensity variations in the backscattered light, that is, the more the interferometric noise exhibited. The more the interferometric noise in the Rayleigh backscattered signal, the poorer the temperature accuracy of the distributed temperature sensor based on the ratio of the Raman anti Stokes to Rayleigh backscattered components. To quantify the interferometric noise affecting the Rayleigh backscattered signal, a mathematical model based on well-known scattering and interferometry theories is developed. Using the developed mathematical noise model, noise powers of approximately -52dBm and -40dBm for coherence lengths of 4m and 24m are respectively obtained...

Optical amplification and signal processing are of great importance to ensure reliable operation of fiber-optic networks. The capacity of optical networks are growing rapidly to deal with the ever-growing Internet traffic demand, which requires optical amplification and signal processing to have ultra-fast response, wide operation bandwidth, flexible operation spectral range and transparency to different modulation formats. In this regard, fiber optical parametric amplifiers (FOPAs), which rely on the efficient parametric process in highly nonlinear fibers, are promising to operate as amplifiers and signal processers in future high-capacity optical networks. This thesis focuses on the advanced schemes of optical amplification and signal processing based on FOPAs to cope with the developing optical networks. / New optical amplifiers are highly desirable for previously unused optical bands to increase aggregate optical communication bandwidth. Raman-assisted FOPAs are promising because they can provide higher gain efficiency than Raman amplifiers and more flexible operation spectral range than the conventional FOPAs. Gain saturation is an important property of parametric amplification, which may result in signal distortion during amplification but can be utilized for optical regeneration. In this thesis, gain saturation characteristics in a Raman-assisted FOPA are experimentally observed and theoretically analyzed through simulations. As compared to a conventional FOPA, gain saturation is deferred with enhanced saturated output power and the saturated gain spectrum is broadened with suppressed signal wavelength dependence in the Raman-assisted FOPA. The novel saturation behaviors are explained by the modification of the parametric pump power and nonlinear phase mismatch by the backward Raman amplification. Moreover, controlling saturation behaviors by tuning the Raman gain on the parametric pump are demonstrated. / Amplification performance of Raman-assisted FOPAs is further investigated, including single-channel amplification incorporating with coherent reception and multi-channel amplification for wavelength division multiplexing (WDM) systems. In the single-channel amplification, sufficient amplification performance for the QPSK signal has been successfully achieved in two Raman-assisted FOPAs with the same signal gain of 19 dB but different pump power combinations. In addition, the FOPA with a higher Raman pump is more advantageous due to the wider gain bandwidth and the deferred signal gain saturation. Nonlinear crosstalk is the major restriction of FOPAs for multi-channel amplification in WDM systems. We propose and demonstrate suppression of cross-gain modulation (XGM) crosstalk and four-wave mixing (FWM) crosstalk using a Raman-assisted FOPA. The performances are compared between FOPAs with and without the Raman pump under the condition of identical unsaturated gains. The reduction of XGM crosstalk utilizes the deferred gain saturation in the Raman-assisted FOPA which implies a larger range of input signal power for a constant gain. On the other hand, the suppression of FWM crosstalk is based on the unique signal power evolution which has a crescent slope along the fiber. Accordingly, the performance of multi-channel amplification has been improved in the Raman-assisted FOPA. / Polarization division multiplexing (PDM) in combination with phase-shift keying (PSK) signals is being increasingly employed to improve the spectral efficiency of optical networks. Gain-saturated FOPA is an attractive approach to reduce the nonlinear phase noise and improve the transmission performance by suppressing the amplitude noise of PSK signals. In this thesis, saturation characteristics of FOPA are investigated in terms of input signal polarizations. Our theoretical analysis and experimental results show that PDM signals exhibit nearly identical saturation behaviors when two orthogonal polarized pumps are applied. In addition, polarization-insensitive gain saturation can be achieved by optimizing the pump powers. We report the experimental demonstration on polarization-insensitive amplitude regeneration of 40-Gb/s DPSK signals and amplitude regeneration of 80-Gb/s PDM RZ-DPSK signals. / 光信號的放大和處理在確保光纖通信網絡的可靠運行中起著至關重要的作用。隨著因特網流量需求的不斷增長，光網絡的容量也在高速增長，這就要求光信號的放大和處理具有超快的響應速度，更大的工作帶寬，靈活可調的光譜範圍以及對不同調制格式的透明度。光纖參量放大器是一種基於高非線性光纖的高效率參量過程的多功能器件，非常適合用於未來高容量光網絡中的光信號放大和處理。本論文將致力於研究基於光纖參量放大器的先進技術以適用於快速發展的光通信網絡中光信號的放大和處理。 / 為了拓展總的光通信帶寬，適用於新的光學波段的新型光放大器是非常重要的。拉曼輔助光纖參量放大器具有高於拉曼放大器的增益效率，與傳統的光纖參量放大器相比更加靈活的工作光譜範圍，是一種優秀的新型光放大器。增益飽和是參量放大過程的一種重要特性，它既可能引進放大過程中的信號損傷，又可用於全光再生。本文通過實驗觀察和理論模擬研究了拉曼輔助光纖參量放大器的增益飽和特性。與傳統的光纖參量放大器相比，拉曼輔助光纖參量放大器需要更高的信號輸入功率以達到增益飽和，具有增強的飽和輸出功率。飽和條件下其增益光譜被展寬，而飽和特性與信號波長的相關性被減弱。通過模擬計算，我們得出這些新穎的飽和特性的物理解釋：反向的拉曼放大過程改變了參量泵浦功率和非線性相位失配在光纖中的分布。另外，通過調節參量泵浦的拉曼增益，我們還展示信號增益飽和特性的控制。 / 我們進一步研究了拉曼輔助光纖參量放大器在信號放大方面的性能，包括了單通道信號的放大和波分復用系統中多通道信號的放大。在單通道信號放大的研究中，我們研究了兩種具有不同泵浦功率組合的放大器，而這兩種放大器都提供19dB的增益。實驗中，我們采用相幹接收對放大後的四相相移鍵控信號進行分析，發現兩種放大器都具有令人滿意的放大效果。同時我們還發現其中具有高的拉曼泵浦功率的放大器更有優勢，因為它能夠提供更大的增益帶寬和更加延遲的信號增益飽和。非線性串擾是光纖參量放大器應用於波分復用系統中多波長信號放大的主要障礙。我們提出拉曼輔助光纖參量放大器可用於抑制多通道信號放大時的交叉增益調制串擾和四波混頻串擾。在我們的研究中，拉曼輔助光纖參量放大器在多通道放大方面的優越性能是通過與具有相同線性增益的傳統光纖參量放大器進行比較體現出來的。拉曼輔助光纖參量放大器的延遲增益飽和說明了在更大的信號輸入光功率範圍內不會引起參量泵浦的明顯減弱，因而可以用於抑制交叉增益調制串擾。另一方面，拉曼輔助光纖參量放大器使信號在光纖中具有獨特的功率演變過程，可用於降低四波混頻串擾。因此，我們利用拉曼輔助光纖參量放大器成功地提高了多通道放大的信號質量。 / 偏振復用技術與相移鍵控調制格式的結合越來越多地被用於提高光網絡的頻譜效率。光纖參量放大器的增益飽和是一種很有吸引力的抑制相移鍵控信號幅度噪聲的方法，可以有效地降低非線性相位噪聲從而提高傳輸性能。本文研究了不同信號偏振情況下光纖參量放大器的增益飽和特性。理論分析和實驗結果都顯示在采用正交偏振的參量泵浦時偏振復用信號具有相同的增益飽和特性。另外，偏振不敏感的增益飽和可以通過調節泵浦功率實現。我們成功展示了40-Gb/s非歸零差分相移鍵控信號的偏振不敏感幅度再生以及80-Gb/s偏振復用歸零差分相移鍵控信號的幅度再生。 / Guo, Xiaojie. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2014. / Includes bibliographical references. / Abstracts also in Chinese. / Title from PDF title page (viewed on 12, September, 2016). / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only.