Wavelength-selective core-to-jacket coupling in optical fiber

Abstract

Mode coupling between the fundamental core mode of an as-drawn optical fiber operating far from cutoff and higher-order modes in the plastic jacketing has been observed. In one fiber, the transmission spectrum of the core exhibited five distinct minima between 1200 and $1900\mathrm{nm}$. By approximating the fiber jacket as an asymmetric slab waveguide of infinite lateral extent, the wavelengths of these transmission features were successfully predicted using coupled-mode theory. Since conditions at the jacket surface influence the transmission spectrum, this coupling effect potentially enables new applications for environmental sensing.