LP Mode Solver


This small Matlab library contains functions for finding and plotting all the LP modes of a step-index fibre under the weakly guided approximation. The function find_LP_modes numerically solves the eigenvalue equation:

\frac{J_{l-1}(u)}{J_l(u)} = - \frac{w}{u} \frac{K_{l-1}(w)}{K_l(w)}

where J_l is a Bessel function of the first kind of order l, K_l is a Bessel function of the second kind of order l and

w^2 = V^2 - u^2

where V is the fibre V number and u is the parameter to be solved.

Download Library | View Readme (PDF)

The images below are example amplitude and intensity plots of an LP mode.


Version History

Release 1 : Original Release
Release 2 : Bug fix in plot_all_LP_modes which was incorrectly choosing which modes were rotationally degenerate