by Chun-kit Chan. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1995. / Includes bibliographical references (leaves 68-[73]). / Chapter 1 --- A High-Speed All-Optical Tunable-Channel Multi-Access (TCMA) Network --- p.1 / Chapter 1.1 --- Introduction --- p.1 / Chapter 1.2 --- Tunable-Channel Multi-Access (TCMA) Networks --- p.4 / Chapter 1.3 --- Protocols For TCMA Networks --- p.5 / Chapter 1.3.1 --- Media Access Procedure For ACTA Protocol --- p.6 / Chapter 1.3.2 --- Cyclc Utilization & Adaptive Algorithm --- p.8 / Chapter 1.3.3 --- Advantages of ACTA Protocol --- p.9 / Chapter 1.4 --- Proposed High-Speed Photonic TDM Implementation --- p.10 / Chapter 1.4.1 --- Centralized Pulse Source --- p.12 / Chapter 1.4.2 --- Channel-Tunable Transmitter --- p.14 / Chapter 1.4.3 --- High Speed All-Optical Demultiplexing --- p.22 / Chapter 1.4.4 --- Timing and Synchronization --- p.23 / Chapter 1.4.5 --- Advantages of the Proposed Scheme --- p.24 / Chapter 1.5 --- Other Network Issues --- p.25 / Chapter 1.5.1 --- Scalability --- p.25 / Chapter 1.5.2 --- Surviability --- p.26 / Chapter 1.5.3 --- Cost-Effectiveness --- p.27 / Chapter 1.6 --- Conclusion --- p.28 / Chapter 2 --- Theoretical Analysis of High Repetition Rate Optical Pulse Multiplication using Fiber Coupler Loop Configuration --- p.29 / Chapter 2.1 --- Introduction --- p.29 / Chapter 2.2 --- Single Coupler Loop Configuration --- p.30 / Chapter 2.3 --- Cascaded Coupler Loop Configuration --- p.34 / Chapter 2.4 --- Discussion --- p.36 / Chapter 2.5 --- Conclusion --- p.38 / Chapter 3 --- Spectrum Analysis of Multichannel CATV Systems --- p.39 / Chapter 3.1 --- Introduction --- p.39 / Chapter 3.2 --- Considerations of Analysis of Multichannel CATV Systems --- p.41 / Chapter 3.3 --- Effects of Incomplete-cycle Sampling --- p.43 / Chapter 3.4 --- Methods to Alleviate the Incomplete-cycle Sampling Effcct --- p.48 / Chapter 3.4.1 --- Windowing --- p.48 / Chapter 3.4.2 --- Correction --- p.54 / Chapter 3.5 --- Nonlinear Distortion in Multichannel CATV Systems --- p.55 / Chapter 3.5.1 --- Two-tone Third Order Distortion Estimation --- p.56 / Chapter 3.5.2 --- Composite Triple Beat Estimation --- p.62 / Chapter 3.6 --- A Procedure of Spectrum Analysis for Multichannel CATV Systems --- p.64 / Chapter 3.7 --- Conclusion --- p.67 / Bibliography --- p.68 / Chapter A --- Implementation of a high-speed TCMA optical network --- p.74 / Chapter A.1 --- System Setup --- p.74 / Chapter A.2 --- Channel-tunable Delay Line Circuit --- p.75 / Chapter A.3 --- DFB Laser diode --- p.76 / Chapter A.4 --- Erbium-doped Fiber Amplifier (EDFA) --- p.76 / Chapter A.5 --- 1 Gb/s to 16 Gb/s Fiber Multiplexer --- p.77 / Chapter A.6 --- Nonlinear Amplifying Loop Mirror (NALM) --- p.77 / Chapter A.7 --- Decision Circuit --- p.78 / Chapter B --- Frequency Assignment Scheme of CATV Systems --- p.79 / Chapter C --- Derivation --- p.80 / Chapter C.1 --- Channel Carrier Power Level Variation with Rectangular Window --- p.81 / Chapter C.2 --- Channel Carrier Power Level With Hanning Window Function ´Ø --- p.82 / Chapter C.3 --- Correction Factor for the Channel Carriers --- p.83 / Chapter C.4 --- Correction Scheme for Distortion Terms --- p.83

by Poon Wing-chak. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1989. / Includes bibliographies.

Hui Yuen Yung. / Thesis submitted in: August 1998. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1999. / Includes bibliographical references (leaves 70-73). / Text in English; abstract also in Chinese. / Hui Yuen Yung. / Acknowledgements --- p.vi / Abstract --- p.vii / Chapter 1 --- Introduction --- p.1 / Chapter 2 --- Second harmonic generation --- p.5 / Chapter 2.1 --- Introduction --- p.5 / Chapter 2.2 --- Maxwell's equations in dielectric media --- p.6 / Chapter 2.3 --- Second harmonic generation --- p.7 / Chapter 2.4 --- Phase matching --- p.8 / Chapter 2.5 --- Quasi phase matching --- p.10 / Chapter 2.6 --- Inversion symmetry --- p.11 / Chapter 3 --- Third order nonlinear optical processes in optical fibers --- p.14 / Chapter 3.1 --- Introduction --- p.14 / Chapter 3.2 --- Optical fibers --- p.15 / Chapter 3.3 --- Third order interaction between waves of same frequency --- p.16 / Chapter 3.4 --- Third order interaction between waves of different frequencies --- p.19 / Chapter 4 --- Multiphoton ionization interference effect --- p.23 / Chapter 4.1 --- Historical development --- p.23 / Chapter 4.2 --- Multiphoton ionization interference effect --- p.26 / Chapter 4.3 --- Periodic ionization --- p.27 / Chapter 4.4 --- Periodic electric field --- p.28 / Chapter 4.5 --- Physical interpretation --- p.29 / Chapter 5 --- Experimental setup --- p.32 / Chapter 5.1 --- Introduction --- p.32 / Chapter 5.2 --- Laser system --- p.32 / Chapter 5.3 --- Optical fibers --- p.33 / Chapter 5.4 --- Coupling light into fibers --- p.34 / Chapter 5.5 --- Detection system --- p.36 / Chapter 5.6 --- Optical layout --- p.36 / Chapter 6 --- Second harmonic generation in optical fibers --- p.40 / Chapter 6.1 --- Introduction --- p.40 / Chapter 6.2 --- Self-preparation in optical fibers --- p.41 / Chapter 6.3 --- Polarization dependence --- p.42 / Chapter 6.4 --- Seeding optical fibers --- p.42 / Chapter 6.5 --- Seeding by varying green light intensity --- p.45 / Chapter 6.6 --- Square dependence of second harmonic generation in optical fibers --- p.46 / Chapter 7 --- Erasure of x(2) grating in optical fibers --- p.56 / Chapter 7.1 --- Introduction --- p.56 / Chapter 7.2 --- Experiment --- p.58 / Chapter 7.3 --- Results --- p.59 / Chapter 7.3.1 --- Erasure by different propagating mode --- p.59 / Chapter 7.3.2 --- Erasure in germanium-doped fiber --- p.60 / Chapter 7.3.3 --- Erasure in erbium-doped fiber --- p.61 / Chapter 7.4 --- Discussion --- p.61 / Chapter 8 --- Conclusion --- p.68 / Chapter 8.1 --- Summary of our work --- p.68 / Chapter 8.2 --- Outlook --- p.69 / Chapter 8.2.1 --- Multiphoton ionization in polymer --- p.69 / Chapter 8.2.2 --- Erasure by blue light --- p.69 / Bibliography --- p.70

Chow Kin Kee. / May, 2003." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2003. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.

Both gain transient and dynamic gain control devices were also designed and fabricated as photonic integrated circuits (PICs). Silicon-based PICs were able to perform dynamic gain tilt compensation by thermo-optic effect. Helium doped SOI rib waveguides were used for power monitoring and is potentially used as monolithic gain tilt compensation device with arrayed waveguide grating (AWG). / Dynamic gain tilt induced by wavelength dependent gain of EDFA leads to power penalty in wavelength division multiplexed systems. Using optical filter with known spectral response, it is possible to detect dynamic gain tilt and a per-band compensation scheme using electronic variable optical attenuators. This was implemented for dynamic gain tilt compensation (DGTC). / Dynamic provisioning of bandwidth and re-configurable optical networks can potentially allow efficient and cost effective deliveries of services based on the actual bandwidth requirement. Optical add/drop multiplexers (OADM) and optical cross-connects (OXC) will be used for such networks but the dynamic provisioning of optical channels may introduce optical power transients because of the slow gain dynamics of erbium doped fiber amplifiers. In this dissertation, the potential problems on using Erbium Doped Fiber Amplifiers (EDFA) in future reconfigurable optical networks are studied and possible solutions are assessed. In particular, the problems of gain transient and dynamic gain tilt were studied experimentally and theoretically. / In saturated EDFA channel add/drop can produce average power fluctuations, in timescales in the microsecond range. The thesis describes how gain transients can be minimized in gain clamped EDFA by optimizing erbium concentrations of EDF. Both simulations and experiments demonstrate that highly doped EDF minimize the transient in gain clamped EDFA. For unclamped EDFA, all-optical feedforward constant output power compensation has been successfully demonstrated using electronic variable optical attenuator (EVOA). / Chan Po Shan. / "August 2006." / Source: Dissertation Abstracts International, Volume: 68-03, Section: B, page: 1813. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2006. / Includes bibliographical references. / 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.

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.

Thesis (Ph. D.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2004. / John A. Buck, Committee Chair ; Stephen E. Ralph, Committee Member ; Gee-Kung Chang, Committee Member ; Rick Trebino, Committee Member ; Glenn S. Smith, Committee Member. Includes bibliographical references (leaves 102-104).

Fiber optical parametric amplifier (FOPA) is undoubtedly one of the most thriving research topics about optical amplifiers during the past decades. The high optical gain, arbitrary gain regions and wavelength conversion with large frequency shift make FOPA outstanding in diverse application areas like the high-speed all-optical communication, wavelength-tunable laser sources and optical imaging systems. Special fiber gain medium and proper pump source are two essential elements in an FOPA setup. As the research interest on FOPAs has recently gradually extended from the conventional 1.5-_m region to the shorter wavelength band at 1 μm, photonic crystal fibers (PCFs) act as the gain media by virtue of their customized dispersion curve and nonlinearity in this band. And the 1-mum laser sources incorporating ytterbium-doped fiber (YDF) as the gain medium have been investigated as well. We prefer all-fiber laser as the pump source not only because of its high output quality but also its compatibility with other fiber systems like FOPA. However, compared with 1.5-_m range, fiber lasers in 1-_m wavelength window have not been fully developed. Most of the laser sources reported in this wavelength range are not all-fiber base. For those few all-fiber reports, the tuning range of the pulsing wavelength is not wide enough, which might limit the performance of the FOPA. In this thesis, we have investigated tunable fiber lasers aiming at becoming the promising pump sources for 1-μm FOPAs. All-fiber lasers with different techniques and operation schemes based on the YDF have been discussed. Tunable ytterbium (Yb) fiber lasers with short pulsed output are important for pulsed-pumped FOPAs in 1 _m. Passive and active mode locking techniques are both commonly employed in short pulse generation. Passive mode-locking laser cavity usually works at the fundamental frequency of the cavity (?MHz) and has the potential to generate ultra-short pulse (? fs) due to its fast recovery time. On the other hand, active mode locking is more agile in terms of the repetition rate, which is synchronized with the external electrical signal. It can be as high as tens of GHz, which is useful for high-speed optical communication, and also can be as low as tens of MHz, which can benefit applications that require high peak power. For an all-fiber mode-locked laser based on YDF, the self-starting of the passive mode locking in 1 _m is more difficult than in 1.5 μm due to the large value of the normal material dispersion in optical fibers in this shorter wavelength range. In this thesis, we have focused on the active mode-locking cavity. Two schemes of actively mode-locked fiber lasers have be demonstrated. One is with a high repetition rate of about 10-GHz at around 1030 nm. The 30-nm tuning range is beneficial to the development of the wavelength-division multiplexing (WDM) technology in the newly developed 1-μm communication band. And on the basis of this scheme, another actively mode-locked fiber laser with a wider tuning range (almost 50 nm) have been achieved by optimizing the length of the YDF inside the cavity. Considering the applications like fiber sensing or spectroscopy where high peak power is more essential and also due to the limitation of our 980-nm pump power, the repetition rate has been lowered down to around 300 MHz in the second scheme. Tunable continuous-wave (CW) fiber lasers in 1 _m have also been discussed. For an all-fiber ring laser cavity, a stable CW output without mode-hopping can be achieved by selecting out single frequency. Various experimental configurations have been proposed for single-longitudinal-mode (SLM) oscillation. We have combined the multiple-ring cavity (MRC) and the saturable absorber in the same fiber laser cavity to facilitate the SLM generation in 1 _m. The tunable CW SLM fiber laser has the potential to build a sweeping source with instantaneous narrow linewidth for optical coherence tomography (OCT) in this range. It can also be utilized as the pump source for CW FOPAs, which is more immune from the walk-off effect between the pulsed pump and the signal, as long as the stimulated Brillouin scattering (SBS) has been suppressed properly. / published_or_final_version / Electrical and Electronic Engineering / Master / Master of Philosophy

With the data explosion brought about by smartphones and tables during the past few years, how to keep these ever-increasing data in a stable, fast and green transmission and exchange environment is among the top problems for researchers in the communication field. As the backbone for the modern communication network, optical fiber communication is currently playing a key role in this on-going technology revolution. The optical amplifier is one of the most powerful tools of the optical communication system to cope with the data explosion. Distributed parametric amplification (DPA), with its potential green characteristics, i.e. noiseless, high-speed response, high power efficiency and wavelength flexibility, provides a promising amplification solution for the next generation of optical communication systems. As on specific type of optical parametric amplification (OPA), DPA is based on the combination of self-phase modulation (SPM), cross-phase modulation (XPM) and four-wave mixing (FWM) effects. DPA’s main difference from OPA lies in the amplification medium. As DPA utilizes the most commonly adopted transmission fiber, i.e. single-mode fiber (SMF) and dispersion-shifted fiber (DSF), the signal transmission can thus be fulfilled simultaneously with the parametric amplification in the same optical fiber: DPA’s configuration also brings another green feature, pump-power recycling, which further enhances the power efficiency of the communication system. As the fundamental study on DPA, first the gain spectrum is investigated. Both single- and two-pump DPAs are presented experimentally for WDM signals. In these experiments, residual pump power recycling is enabled by a concentrated photovoltaic (CPV) cells, Moreover, through experimental comparison with another important distributed amplification technology, distributed Raman amplification (DRA), DPA’s advantages over DRA are demonstrated. When considering similar performance levels, DPA needs much lower pump power than DRA, which in return improves the system power efficiency. The performance of DPA cannot be judged unless it is assessed in more advanced application scenarios. Thus more advanced studies on DPA are conducted. The modulation format transparency is first presented with both phase (differential phase-shift keying (DPSK)) and intensity (on-off keying (OOK)) modulation formats, and our experimental results show the superiority of DPSK over traditional OOK. Furthermore, from the perspective of wavelength flexibility, we have demonstrated, for the first time to the best of our knowledge, a DPA system at the 1.3μm telecommunication window, which provides a potentially green amplification scheme at this transmission band. All these experiments, to a certain extent, certify the feasibility of DPA to become a green optical fiber amplifier. Finally, to demonstrate DPA’s compatibility within a more complicated communication system, we propose a power–efficient UWB/DPA system for the “last mile”. After experiments on photonic UWB pulse generation and the supporting DPA system, the hybrid UWB/DPA system is demonstrated with preliminary simulation results. My research efforts presented in this thesis all aim at the practical application of the DPA scheme into the next-generation of green communication systems. If further armed with the phase-sensitive configuration, DPA’s potential as a green amplifier will be further augmented. / published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

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