An efficient method for calculating cutoff frequencies in optical fibers with arbitrary index profiles

An accurate and simple method of calculating the cutoff frequencies of scalar modes in a fiber having an arbitrary refractive-index profile, including discrete numerical data from profile measurements, is proposed. First, the cutoff problem is transformed into a general matrix eigenvalue problem and then cutoff frequencies as the eigenvalues of a real symmetric matrix are evaluated. Representative test examples have been computed to illustrate the accuracy, reliability, and efficiency of the algorithm proposed.