This thesis presents a study of light propagation in seven-core fiber using a numerical modeling tool and experimental observation. The coupling of light between cores in a Multi-Core Fiber (MCF), or crosstalk, has been investigated using the Eigen mode expansion method. Additionally, we give a full description of the basics for designing and manufacturing single-mode, MCF using the stack and-draw process. Finally we propose a novel type of fiber probe which can be used for many applications such as fluorescence signal collection and spectral filters.
Chapter 1 introduces and reviews the properties and the basic principles of optical fiber light guiding, the application of fiber optical probes to fluorescence spectroscopy and their benefits over other methods. Approximation Approximation formulas for light collection efficiency are analytically developed. Different types of optical fiber fluorimeter probes are also outlined. Single fiber probes in which the excitation and the emission radiation transmitted are reviewed. Then double fiber probes in which one fiber guides the excitation to the sample and the other collects the emission radiation to the detector are presented. Fiber optic bundle probes, in which more than one fiber is used for light collection, are also reviewed.
In Chapter 2, the theory of core-to-core coupling in homogenous and heterogeneous (MCFs) are presented. Then mode coupling dynamics in homogenous and identical seven-core fiber are computed. The coupling behavior is explained by two models. First, by expressing the field solution in a fiber as an expansion of its modes, the power exchange between cores, and therefore the nature of the coupling, can be determined. In addition, coupled mode theory, an analytical model for predicting coupling, is summarized.
In the third chapter the basics for designing and manufacturing a single-mode, seven-core fiber using the stack-and-draw process is described. Then a homogeneity test is applied to determine whether the designed and manufactured geometries of the fabricated seven-core optical fiber are matched.
In chapter 4 the modal characteristics and the mode field distribution of the supermodes inside a strongly coupled seven-core fiber are investigated using numerical simulations. Then the Single mode-Multicore-Single mode fiber structure (SMS) constructed by splicing two identical single-mode fibers at both ends of a short length of a seven-core fiber has been studied. The study should be useful in the design of a novel wavelength filters for spectroscopic applications.
In chapter 5 the performance of the SMS structure amongst the variation of the MCF length in the wavelength range 1510 nm to 1580 nm has been studied in both experiment and simulation. Then the Eigen mode expansion method has been used to study and simulate various SMS devices by changing the lattice parameters and core diameters of the seven-core fiber section.
Finally, Chapter 6 draws conclusions from the research and discusses future work prospects in this research field.
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