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Early methods of optical fiber communication systems haven't been much promising in terms of efficiency. The presence of various impairments in the fiber channel has forced researchers to uncover solutions in order to minimize those effects. With the advancement of technology, optical solutions were finally easier to implement in the system. To this day, optical compensation methods are still found to be as the best way to minimize fiber impairments. However, such technique does introduce enormous complexity to the system, in addition to a large cost. For that reason, the main focus had to shift to an alternative method. Electrical compensation techniques have provided the factor of simplicity to the optical communication system, not to mention that they are relatively cheaper than optical compensators. Furthermore, electrical schemes were found to handle fiber impairments in a relatively efficient manner. In this thesis, an optical fiber communication scheme using the direct-detection method is simulated. A frequency shifter in the optical domain will be used for the system to have a coherent like detection. At the receiver's side, a linear equalizer is realized to offset the linear effects caused by the fiber. To our knowledge, this will mark the first direct detection transmission system to pass the one thousand kilometre mark in fiber length. Furthermore, we simulate another optical fiber communication design using the coherent detection. A nonlinear compensator adapting the Volterra approach will be used to offset nonlinear impairments. Such performance will be compared to that of a linear compensator. Design trade-offs will be analyzed, and the nonlinear compensator is found to a improve performance when a dispersion compensation fiber (DCF) is introduced in the optical domain. / Thesis / Master of Applied Science (MASc)

A novel type of alternating-current (AC) powder electroluminescent (EL) device that relies on nanowire-phosphor heterogeneous junction structure has been developed. It shows promise for manufacturing of highly stable powder EL devices. To pursue this goal, manganese ion (Mn2+)-doped zinc germanate (Zn2GeO4:Mn) oxide phosphor was synthesized and used as EL powder material for the fabrication of the new types of AC powder EL devices. The Zn2GeO4:Mn oxide phosphor powder could eliminate the well-known degradation problem of zinc sulfide (ZnS)-based AC powder EL devices predominant in the current marketplace. In order to realize a high brightness at a relatively low operating voltage, a conductive semiconductor nanowire architecture using zinc oxide (ZnO) and copper oxide (CuO) nanowires with sharp-tip features, was created and integrated into conventional AC powder EL structures. Particularly, vertically-aligned n-type ZnO nanowires arrays were successfully synthesized on a Zn2GeO4:Mn polycrystalline substrate for the first time, and the growth behavior using a chemical vapor deposition (CVD) process was investigated. The density of the ZnO nanowires could be effectively controlled by some experimental parameters, such as the density of gold catalyst nanoparticles, and spatial distance between substrate and CVD source powders. This novel ZnO nanowire-decorated Zn2GeO4:Mn phosphor architecture was used to fabricate top-emission AC powder EL devices. On the other hand, a vertically-aligned ZnO nanowire array was directly synthesized on a thin film indium-tin-oxide (ITO)-coated glass substrate for fabrication of bottom-emission AC powder EL device. The nanowires were adopted to form heterogeneous junction structures between the tips of the nanowires and the Zn2GeO4:Mn EL powders, so that the composites could have a similar electrical field enhancement as in the needle-like CuxS precipitates within widely-used ZnS:Cu EL powder materials. The behavior of these top- and bottom- emission AC powder EL devices was also studied. Alternatively, vertically-aligned p-type CuO nanowires were prepared by a thermal oxidation method. Reliable heterogeneous junction structures were formed by a simple drop-coating method. The CuO nanowire-based AC powder EL device has excellent brightness maintenance with a loss of luminescent intensity under 1 % at over 10 cd/m2 luminance during 360 hours of operation. The integrating of semiconductor nanowires into conventional AC powder EL device structures offers the very promising prospect of fabrication of simple, low-cost, scaled-up EL devices that could fundamentally solve the limited operational lifetime of current ZnS-based AC powder EL devices. / Thesis / Doctor of Philosophy (PhD)