35 research outputs found

    All-optical switching and variable delay using nonlinear optical signal processing techniques.

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    Cheng, Lap Kei.Thesis (M.Phil.)--Chinese University of Hong Kong, 2008.Includes bibliographical references.Abstracts in English and Chinese.ABSTRACT --- p.I摘要 --- p.IIACKNOWLEDGEMENTS --- p.VTABLE OF CONTENTS --- p.IVINTRODUCTION --- p.0Chapter 1.1 --- Different ways to achieve all-optical tunable delay --- p.2Chapter 1.1.1 --- Optical buffer realized with optical switching --- p.2Chapter 1.1.2 --- Slow light technique --- p.3Chapter (i) --- Basics of slow light --- p.4Chapter (ii) --- Slow light via electromagnetically induced transparency (EIT) --- p.6Chapter (iii) --- Slow light via coherent population oscillation (CPO) --- p.7Chapter (iv) --- Slow light via optical parametric amplification (OPA) --- p.8Chapter (v) --- Slow light via stimulated Raman and Brillouin scattering --- p.8Chapter 1.1.3 --- Tunable delay using wavelength conversion together with chromatic dispersion --- p.10Chapter 1.1.4 --- Comparison of different schemes for constructing all-optical delay line --- p.11Chapter 1.2 --- Overview of the thesis --- p.12References --- p.14ALL-OPTICAL SWITCHING OF DPSK SIGNAL IN AN SOA USING NONLINEAR POLARIZATION ROTATION --- p.18Chapter 2.1 --- Introduction --- p.19Chapter 2.2 --- Birefringence and nonlinear polarization rotation --- p.20Chapter 2.3 --- Differential-phase-shift keying (DPSK) modulation format --- p.22Chapter 2.4 --- Experimental setup --- p.23Chapter 2.5 --- Experimental results --- p.25Chapter 2.6 --- Conclusion --- p.29References --- p.30WIDEBAND SLOW LIGHT VIA STIMULATED BRILLOUIN SCATTERING IN AN OPTICAL FIBER USING A PHASE-MODULATED PUMP --- p.32Chapter 3.1 --- Introduction --- p.33Chapter 3.2 --- Stimulated Brillouin scattering (SBS) --- p.34Chapter 3.3 --- Slow light via SBS --- p.35Chapter 3.4 --- Experimental setup --- p.37Chapter 3.5 --- Experimental result --- p.39Conclusion --- p.42References --- p.43SIGNAL WAVELENGTH TRANSPARENT SBS SLOW LIGHT USING XGM BASED WAVELENGTH CONVERTER AND BRILLOUIN FIBER LASER --- p.45Chapter 4.1 --- Introduction --- p.46Chapter 4.2 --- Brillouin fiber laser and XGM wavelength converter --- p.47Chapter 4.3 --- Operating principle --- p.50Chapter 4.4 --- Experimental setup and results --- p.51Conclusion --- p.56References --- p.57ALL-OPTICAL TUNABLE DELAY LINE FOR CHANNEL SELECTION IN A 40-GB/S OPTICAL TIME DIVISION MULTIPLEXING SYSTEM --- p.59Chapter 5.1 --- Introduction --- p.60Chapter 5.2 --- Principle of four-wave mixing --- p.61Chapter 5.3 --- Channel selection in an OTDM system --- p.63Chapter 5.4 --- Experimental setup --- p.64Chapter 5.5 --- Experimental results --- p.67Conclusion --- p.70References --- p.71TUNABLE OPTICAL DELAY WITH CSRZ-OOK TO RZ-OOK OPTICAL DATA FORMAT CONVERSION USING FOUR-WAVE MIXING WAVELENGTH CONVERSION AND GROUP VELOCITY DISPERSION --- p.73Chapter 6.1 --- Introduction --- p.74Chapter 6.2 --- Carrier-Suppressed Return-to-Zero --- p.76Chapter 6.3 --- Operating Principle --- p.77Chapter 6.4 --- Experimental setup --- p.79Chapter 6.5 --- Experimental result --- p.81Conclusion --- p.86References --- p.87CONCLUSION --- p.90Chapter 7.1 --- Summary of work --- p.90Chapter 7.2 --- Prospects of future work --- p.92APPENDIX: LIST OF PUBLICATIONS

    NONLINEAR OPTICS IN HYDROGENATED AMORPHOUS SILICON (A-SI:H) WAVEGUIDES

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    Silicon photonics combines wide-bandwidth capability afforded through optics with well-developed nano-fabrication technology, allowing for short-range communication at low cost, with low operating power and compact device footprints. In order to compete with traditional copper wiring, optical interconnects must be integrated vertically for maximum integration density. Crystalline silicon (c-Si) cannot be deposited; only epitaxially grown or bonded at high temperature thereby destroying the electronic devices and is consequently limited to single layer integration. Here we investigate a new silicon photonic material, hydrogenated amorphous silicon (a-Si:H). This material can be deposited at a low temperature 150 ~300 degree C within the CMOS thermal budget and is already available in the current fabrication process line. Nonlinear optical effects allow ultra-fast time scale all-optical signal processing. However, in c-Si the nonlinear coefficient is low; therefore high input power is required for operation. A-Si, due to its unique band structure, has an order of magnitude higher nonlinear coefficient than c-Si. This high nonlinearity enables all-optical nonlinear applications at very low powers. The first part of this dissertation will focus on the design and fabrication of the a-Si:H waveguide. The optical properties of the waveguide are measured and analyzed. Secondly, using the highly-nonlinear a-Si:H waveguide, I will discuss our demonstrations including: 1) broad-bandwidth wavelength conversion, 2) low power time-domain demultiplexing, 3) all optical signal regeneration, 4) short pulse characterization via frequency resolved optical gating (FROG), 5) broad-band optical parametric amplification and oscillation, and 6) correlated photon-pair generation

    Short-pulse propagation in fiber optical parametric amplifiers

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    Dispersion-managed Breathing-mode Semiconductor Mode-locked Ring Laser

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    A novel dispersion-managed breathing-mode semiconductor mode-locked ring laser is developed. The breathing-mode designation derives from the fact that intracavity pulses are alternately stretched and compressed as they circulate around the ring resonator. The pulses are stretched before entering the semiconductor gain medium to minimize the detrimental strong integrating self-phase modulation and to enable efficient pulse amplification. Subsequently compressed pulses facilitate bleaching the semiconductor saturable absorber. The intracavity pulse compression ratio is higher than 50. Down chirping when compared to up chirping allows broader mode-locked spectra and shorter pulse generation owing to temporal and spectral semiconductor gain dynamics. Pulses as short as 185 fs, with a peak power of ~230 w, and a focused intensity of ~4.6 gw/cm2 are generated by linear down chirp compensation and characterized by shg-frog method. To our knowledge, this is the highest peak power and the shortest pulse generation from an electrically pumped all-semiconductor system. The very good agreement between the simulated and the measured results verifies our understanding and ability to control the physical mechanisms involved in the pulse shaping within the ring cavity. Application trends such as continuum generation via a photonic crystal fiber, two-photon fluorescence imaging, and ultrafast pulse source for pump-probe experiments are demonstrated

    Photonic platform and the impact of optical nonlinearity on communication devices

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    It is important to understand properties of different materials and the impact they have on devices used in communication networks. This paper is an overview of optical nonlinearities in Silicon and Gallium Nitride and how these nonlinearities can be used in the realization of optical ultra-fast devices targeting the next generation integrated optics. Research results related to optical lasing, optical switching, data modulation, optical signal amplification and photo-detection using Gallium Nitride devices based on waveguides are examined. Attention is also paid to hybrid and monolithic integration approaches towards the development of advanced photonic chips

    Management of fiber physical effects in high-speed optical communication and sensor systems

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    Ph.DDOCTOR OF PHILOSOPH

    The application of SOA for dispersion management of 2D-WH/TS codesin incoherent OCDMA system

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    In high data rate optical fibre communication networks, dispersion phenomenon plays a pivotal role. It is important to investigate the dispersion effects in a multi-wavelength picosecond optical code division multiple access (OCDMA) system. This research is focused on the analysis of the effects of fibre dispersion on the OCDMA autocorrelation; and how these effects can be resolved in a tuneable way so that the originally recovered OCDMA autocorrelation function at the decoder receiver can be revived without further manual adjustment of fibre (SMF-28) cable lengths.;The environmental effects and the subsequent mitigation process are also investigated further in this research. The chirp in OCDMA is examined experimentally and analytically in an initiative to find the more in-depth understanding of finely tuneable chromatic dispersion (CD) compensation technique in a coarsely compensated link by using semiconductor optical amplifier (SOA). A practical investigation was carried over a partially CD compensated 17 km bidirectional testbed between the University of Strathclyde and the University of Glasgow to perform the fine-tuning of CD adjustment using SOA.;A 19.5 km SMF-28 fibre spool was also used in an environmental chamber to investigate the temperature induced dispersion effects and subsequent mitigation. The tuneable dispersion compensation measures are vital to ensure the high data rate optical communication using an all-optical approach in future data network end-points where the advantages of ultra-high speed optical communication bandwidth are at present disrupted due to opto-electronic conversions commonly known as 'electronic bottlenecks'.In high data rate optical fibre communication networks, dispersion phenomenon plays a pivotal role. It is important to investigate the dispersion effects in a multi-wavelength picosecond optical code division multiple access (OCDMA) system. This research is focused on the analysis of the effects of fibre dispersion on the OCDMA autocorrelation; and how these effects can be resolved in a tuneable way so that the originally recovered OCDMA autocorrelation function at the decoder receiver can be revived without further manual adjustment of fibre (SMF-28) cable lengths.;The environmental effects and the subsequent mitigation process are also investigated further in this research. The chirp in OCDMA is examined experimentally and analytically in an initiative to find the more in-depth understanding of finely tuneable chromatic dispersion (CD) compensation technique in a coarsely compensated link by using semiconductor optical amplifier (SOA). A practical investigation was carried over a partially CD compensated 17 km bidirectional testbed between the University of Strathclyde and the University of Glasgow to perform the fine-tuning of CD adjustment using SOA.;A 19.5 km SMF-28 fibre spool was also used in an environmental chamber to investigate the temperature induced dispersion effects and subsequent mitigation. The tuneable dispersion compensation measures are vital to ensure the high data rate optical communication using an all-optical approach in future data network end-points where the advantages of ultra-high speed optical communication bandwidth are at present disrupted due to opto-electronic conversions commonly known as 'electronic bottlenecks'

    Multi-wavelength optical Kerr effects in high nonlinearity single mode fibers and their applications in nonlinear signal processing.

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    Kwok Chi Hang.Thesis (M.Phil.)--Chinese University of Hong Kong, 2006.Includes bibliographical references.Abstracts in English and Chinese.Chapter Chapter 1 --- Introduction --- p.1Chapter 1.1 --- All-Optical Signal Processing in Optical Communications --- p.2Chapter 1.2 --- Fiber-Based Optical Kerr Nonlinear Switches --- p.5Chapter 1.3 --- Highly Nonlinear Fibers --- p.6Chapter 1.4 --- Objectives and Scope of Study --- p.8Chapter 1.5 --- Summary --- p.9Chapter Chapter 2 --- Optical Nonlinearity --- p.14Chapter 2.1 --- Fiber Nonlinearity --- p.15Chapter 2.2 --- Dispersion --- p.21Chapter 2.3 --- Cross-Phase Modulation --- p.26Chapter 2.4 --- Cross-Polarization Modulation --- p.29Chapter Chapter 3 --- Fibers: The Nonlinear Media --- p.47Chapter 3.1 --- Average Dispersion --- p.48Chapter 3.2 --- Longitudinal Dispersion Map --- p.53Chapter 3.3 --- Nonlinear Refractive Index and Nonlinear Coefficient --- p.57Chapter 3.4 --- Electrostrictive Contribution --- p.62Chapter 3.5 --- List of the Fiber Properties --- p.66Chapter Chapter 4 --- Multi-Wavelength Nonlinear Signal Processing --- p.69Chapter 4.1 --- Challenge --- p.70Chapter 4.2 --- Applications --- p.72Chapter 4.3 --- Proposed System Application --- p.110Chapter Chapter 5 --- Conclusion and Future Work --- p.114Chapter 5.1 --- Comparisons between Proposed and Existing Approaches --- p.114Chapter 5.2 --- Conclusion of the Dissertation --- p.115Chapter 5.3 --- Prospects and Directions of Future Work --- p.117Appdenix A Numerical Model for Dispersion Calculation --- p.IAppdenix B Simulation Model of Wide Band Cross-Polarization Switch --- p.IIIAppdenix C Simulation Model of Spectral Filtering under XPM --- p.VIList of Publications --- p.I
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