The Formation of Fringes of Equal Chromatic Order across Double Clad Fiber in the Presence of High Power Lasers

Abstract

Multiple-beam fringes of equal chromatic order interferometry is a powerful technique to extract optical properties over a continuous range of spectrum. In this paper we develop a theory for the spectral shape of the fringes of equal chromatic order (FECO) that are formed across a double-clad fiber. The modified single term Sellmeier dispersion formula is used to construct the refractive index dispersion curves for the liquid, claddings, and core. Expressions for the paraxial optical path length for several rays passing through the fiber and the liquid are developed. The condition of bright fringe is applied to get an analytical expression for the spectral shape of the FECO across a double-clad fiber with an elliptical/circular inner cladding. A potential application of this theory is to determine the dispersion of Kerr constant of the claddings and the core of the fiber. To illustrate the theory and its application, simulation examples are provided and discussed.

FECO fringes for investigating the effect of grafting process on the dispersion properties of polyamaide‐6 fibers

“…Multiple‐beam fringes of equal chromatic order, FECO, are generated when a wedge is illuminated by a parallel beam of white light and crossed with a spectrometer. The system resolved the white light into the visible spectrum (Omar & Abd El‐Maksoud, 2016). Consequently, the dispersion study can be carried out in one‐go, and the high number of the used wavelengths makes the calculation more accurate (El‐Zaiat, 2005).…”