Title :
Analysis of modal cutoffs of radially inhomogeneous two-core optical fibers by circular harmonics expansion method
Author :
Chang, Chih-Sheng ; Chang, Hung-Chun
Author_Institution :
Dept. of Electr. Eng., Nat. Taiwan Univ., Taipei, Taiwan
fDate :
12/1/1996 12:00:00 AM
Abstract :
A scalar theory based on generalization of the circular harmonics expansion method combined with the finite element method is formulated to determine cutoff values for higher order normal modes on the two-core fiber with radially inhomogeneous core index profiles under the weakly guiding approximation. The validity of the field expansion expression in the derived generalized circular harmonics expansion method is proved rigorously by expanding the Green´s function for the Laplace equation in a surface integral equation into generalized circular harmonics. Numerical examples are given for the two identical-core cases with power-law core index profiles. Our method is shown to be able to provide exact cutoff values for the touching-core case
Keywords :
Green´s function methods; approximation theory; finite element analysis; harmonic analysis; integral equations; optical fibre theory; refractive index; Green´s function; Laplace equation; circular harmonics expansion method; field expansion expression; finite element method; generalized circular harmonics expansion method; higher order normal modes; identical-core cases; modal cutoffs; power-law core index profiles; radially inhomogeneous core index profile; radially inhomogeneous two-core optical fibers; scalar theory; surface integral equation; touching-core case; two-core fiber; weakly guiding approximation; Cutoff frequency; Eigenvalues and eigenfunctions; Harmonic analysis; Integral equations; Laplace equations; Optical coupling; Optical fiber couplers; Optical fiber devices; Optical fiber theory; Optical fibers;
Journal_Title :
Lightwave Technology, Journal of
