With ever-increasing networking bandwidth demand imposed by data explosion in recent years, optical source generation plays a more and more important role in fiber optical communications. Today wavelength-division-multiplexing (WDM) which refers to encoding independent information onto different wavelengths becomes a widely used technique to increase the transmission bandwidth. However, current WDM system usually requires one single laser source for each distinct wavelength channel which is relatively expensive and cumbersome. Moreover, current WDM system is usually confined to conventional band (C-band) due to the lack of proper gain medium outside C-band. Thus simultaneously generating multiple wavelengths beyond C-band is highly desirable and attractive. Fiber optical parametric amplifier (FOPA) which is based on χ^((3)) nonlinear effect of optical fiber exhibits remarkable properties such as high gain, wide gain bandwidth, and ultra-fast response and could act as a promising candidate for amplifying optical signal beyond C-band. In this thesis I propose and demonstrate several multiwavelength optical sources by taking advantaging of the parametric process. I first experimentally demonstrate the dual-cavity mode-locked FOPO by utilizing two intracavity branches which share the same highly-nonlinear dispersion-shifted fiber (HNL-DSF) as gain medium. Simultaneous generation of 10-GHz pulse train at four different wavelengths located in short wavelength band (S-band) and long wavelength band (L-band) can be achieved. I then introduce the first dispersion distributed FOPO at 10-GHz. With this more advanced cavity configuration, narrower wavelength spacing and wider tuning range in the S- and L-band can be obtained more efficiently in a single cavity. In addition to multiwavelegnth 10-GHz FOPO, multiwavelength FOPO at higher repetition rate beyond C-band is also of great interest in fiber optical communication. I then achieve the first widely tunable 40-GHz dual-wavelength pulsed FOPO. Good quality pulses in both S-and L-band with relatively short duration and low timing jitter can be generated simultaneously. Apart from the parametric process in uniform fiber, I also explore the parametric process in dispersion oscillating fiber (DOF) whose dispersion is periodically modulated along the propagation direction. Based on quasi-phase matched parametric process in DOF, we generate two pairs (quad-wavelength) of modulation instability (MI) side lobes simultaneously. We then numerically and experimentally investigate the spectral correlation between multiple MI by leveraging the dispersive Fourier transformation method. My research efforts presented in this thesis will show the versatility of parametric process for generating multiwavelength optical waves. These schemes have the potential to become efficient optical sources for optical communication beyond C-band. / published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

This thesis is concerned with the study of dynamic wavelength assignment in wavelength division multiplexed (WDM) passive optical networks (PONs), which is one option for implementing WDM in access networks. A discrete event simulation is developed using the Block Oriented Network Simulator (BONeS) package to compare a WDM PON using dynamic wavelength allocation with one utilizing fixed wavelengths. The model is used in conjunction with a traffic profile constructed using market research data to show bandwidth savings for dynamic assignment of between 4 and 20 % depending on the number of customers and the services distributed. It is shown that the alternative approach of using the Erlang laws underestimates these benefits. An upstream protocol for real-time services with a Fibre To The Cabinet (FTTCab) configuration is developed for single wavelength PONs. It is shown that using connectionbased information does not improve the performance of such a protocol. A segment based protocol which provides timing information on cell arrivals to reduce CDV is modelled and optimized. The results show that a frame of 766 ps divided into 10 segments allows the International Telecommunication Union (ITU) delay and cell delay variation (CDV) targets to be met. The protocol and modelling process is then extended to a WDM system with multiple service classes and non-negligible tuning times. A mechanism for masking tuning latencies which achieves a throughput efficiency of over 98% is designed and modeled. An improvement in performance is then demonstrated for rapid retuning at frame level compared with wavelength assignment at connection set-up. Finally, a new architecture for transferring the tunable devices from the optical network units (ONUs) to the optical line termination (OLT) is proposed. The reduction in the number of tunable components enables cost savings. The efficient transmission of broadcast and multicast traffic is demonstrated using this architecture.

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Wavelength reuse techniques for bidirectional ultra-wide band (UWB) over fiber (UWBoF) networks are presented. The downstream optical signal from the central station (CS) is reused for upstream data transmission with the original data erased at the base station (BS). Two wavelength reuse schemes for the generation of a clear optical carrier at the BS are theoretically analyzed and experimentally demonstrated. In the first scheme, the wavelength reuse is based on phase-modulation to intensity-modulation (PM-IM) conversion and destructive interferencing using a polarization modulator (PolM) and a fiber Bragg grating (FBG). A theoretical analysis is performed which is verified by an experiment. In the second scheme, the wavelength reuse is based on injection locking of a Fabry–Pérot laser diode (FP-LD) and polarization multiplexing. The UWB injection signal contributes to better BERs of both downstream and upstream services and a lower power penalty cause by the wavelength reuse of the whole system than the baseband signal. A bidirectional point-to-point transmission of over a 25-km single-mode fiber (SMF) using a single wavelength from the CS in each scheme is demonstrated.

Thesis (Ph.D.)--University of Melbourne, Dept. of Electrical and Electronic Engineering, 2002. / Typescript (photocopy). Includes bibliographical references.

Thesis (M.Eng.). / Written for the Dept. of Electrical and Computer Engineering. Title from title page of PDF (viewed 2007/08/29). Includes bibliographical references.

Thesis (M.App.Sc.) - Carleton University, 2002. / Includes bibliographical references (p. 85-89). Also available in electronic format on the Internet.

Thesis (Ph. D.)--Ohio State University, 2003. / Title from first page of PDF file. Document formatted into pages; contains xxvii, 229 p. : ill. Advisor: Ming-Tsan Mike Liu, Department of Computer and Information Science. Includes bibliographical references (p. 219-229).

Wavelength reuse techniques for bidirectional ultra-wide band (UWB) over fiber (UWBoF) networks are presented. The downstream optical signal from the central station (CS) is reused for upstream data transmission with the original data erased at the base station (BS). Two wavelength reuse schemes for the generation of a clear optical carrier at the BS are theoretically analyzed and experimentally demonstrated. In the first scheme, the wavelength reuse is based on phase-modulation to intensity-modulation (PM-IM) conversion and destructive interferencing using a polarization modulator (PolM) and a fiber Bragg grating (FBG). A theoretical analysis is performed which is verified by an experiment. In the second scheme, the wavelength reuse is based on injection locking of a Fabry–Pérot laser diode (FP-LD) and polarization multiplexing. The UWB injection signal contributes to better BERs of both downstream and upstream services and a lower power penalty cause by the wavelength reuse of the whole system than the baseband signal. A bidirectional point-to-point transmission of over a 25-km single-mode fiber (SMF) using a single wavelength from the CS in each scheme is demonstrated.

Page 12 was not included in the thesis. / <p> This work extends the knowledge about the excited electronic states of thioformaldehyde. Survey work is reported over the wavelength region from 230 nm to 180 nm and four electronic transitions are identified. These are assigned as the 1Al(π,π*), 1B2(n,3s), 1Al(n,3py) and 1B2(n,3pz) systems.</p> <p> A vibrational and rotational analysis of the first two systems has been undertaken. The results of these analyses indicate that the molecule remains planar or nearly so in both the 1Al(π,π*) and the 1B2 (n,3s) transitions. This behaviour is contrasted to that of similar molecules which are known to be non-planar in these electronic states and reasons are offered for this observation. The substituted geometry for thioformaldehyde in the 1B2(n,3s) state has been calculated and provides insight into the changes which occur in the molecule on electronic excitation.</p> / Thesis / Doctor of Philosophy (PhD)