Basic properties of ring-index optical fibres

This work analyses theoretically, technologically and practically a class of low-loss single-mode optical fibers with ring refractive index profile. The fibers are considered for long distance signal transmission as well as photonic signal processing. Trunk transmission, ring index fibers have shifted and flattened dispersion characteristics and much larger effective area as compared with standard step-index single-mode. Signal processing, device oriented, ring-index fibers have a unique capability of transmitting either quasi planar modes for large ring diameters or the second order mode in a quasi single-mode regime at lossy discrimination of the fundamental mode, for small ring diameters. Ring-index fibres can maintain singlemode transmission for considerable values of normalized frequency (much larger than cutoff for classical single mode fibres) for particular cases of the refractive index profile. Theoretically predicted features of single-mode ring index fibers were confirmed experimentally on samples manufactured by the author in cooperation with TU of Białystok. Parts of the work were published in Optica Applicata and reprinted with permission. Part of the work was realized within the KBN grant 4-T08D-22 submitted to Technical University of Białystok.