17 June 2009 Characterization of optical fibers by digital holographic interferometry
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Abstract
The refractive index distribution over a cross-section of an optical fiber can differ between core and cladding, can vary over the core in graded index fibers, or may even have a more complicated form in polarization preserving fibers. Besides this intended variations the refractive index may vary due to a loading of the fiber like pressure or bending or due to a faulty production. Digital holographic interferometry is a suitable means for measuring the refractive index distribution. In the experiments reported here the fiber is embedded into an index matching fluid, which is mixed so as to match the index of the cladding. Phase-shifted digital holograms are recorded and the interference phase distribution is calculated. From a single demodulated interference phase distribution the refractive index field is determined by an algorithm based on a model which takes into account the known symmetry of the fiber. It can be shown that the obtained accuracy is better than that of classical two-beam interferometry. Results of experiments with step-index, with graded index, and with polarization preserving fibers are demonstrated.
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Hamdy H. Wahba, Hamdy H. Wahba, Thomas Kreis, Thomas Kreis, "Characterization of optical fibers by digital holographic interferometry", Proc. SPIE 7389, Optical Measurement Systems for Industrial Inspection VI, 73890K (17 June 2009); doi: 10.1117/12.826854; https://doi.org/10.1117/12.826854
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