7 May 2015 Light-guidance in step-index fibers with non-circular shaped core
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Step-index multimode fibers with non-circular core are becoming popular and offer several interesting new light-guiding properties, which can be studied with an emphasis on selective modes or ray patterns. Observing the far-field profile at the fiber output, ray-conversion can be determined, taking the azimuthal angle defined in respect to an adjusted reference into account. Using the inverse far-field method at one laser wavelength, the numerical aperture (NA) of these specialty fibers is determined as a function of excitation condition, such as input angle and rotation around the fiber axis. Further angledependent analysis of ring-shaped far-field pattern at the fiber output resulted in significant differences between the fibers with non-circular core shapes and classic circular fibers. In addition, with squared core fibers, the near- and farfield pattern at their respective fiber output were varying due to rotating the fiber around the fiber axis at their input side. Especially, a disturbance of the azimuthally homogenous ring shape was observed using input angles close to the numerical aperture of the fiber.
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Jan Heimann, Jan Heimann, Philipp Raithel, Philipp Raithel, Tim Tobisch, Tim Tobisch, Mathias Belz, Mathias Belz, Karl-Friedrich Klein, Karl-Friedrich Klein, } "Light-guidance in step-index fibers with non-circular shaped core", Proc. SPIE 9507, Micro-structured and Specialty Optical Fibres IV, 95070R (7 May 2015); doi: 10.1117/12.2182346; https://doi.org/10.1117/12.2182346

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