Characteristics of Near-Surface-Core Optical Fibers

A near-surface-core optical fiber is proposed that consists of a cladding and a circular or an elliptical core close to the surface of the cladding. The finite element method (FEM) is utilized to analyze characteristics of the near-surface-core optical fiber, including the mode characteristic, birefringence, and evanescent field. The results reveal that the near-surface-core optical fiber has polarization- preserving properties and a non-zero cut-off frequency for the fundamental mode. The near-surface-core optical fiber has a strong evanescent field due to a small distance between the core and the ambient medium and is a promising candidate for evanescent wave sensors. The near-surface-core optical fiber has an interesting phenomenon of surface-enhanced optical effect, which is similar to that of the nanofiber.