Perturbation theory for the evaluation of the normalised cutoff frequencies in radially inhomogeneous fibres

Simple Empirical Formulae for Cutoff Frequencies of Few Moded Graded Index Fibers and Index Profile Determination

“…In Table 3 we have presented similar results for the trapezoidal index profile. General- ly, the analytical approximations for the cutoff frequencies available in the literature hold only for the LPn mode [7,[10][11]. As the formulae of Love [15] hold for any mode, we have compared the results obtained by our formulae with those of Love.…”

“…A number of methods, such as the perturbation method [7,11], the power series expansion method [8], the modified WKB method [9], the direct integration iteration method [10], the matrix method [12] and other kinds of numerical methods [3,[13][14] have been proposed to compute the normalised cutoff frequencies of modes of arbitrarily graded index fibers, each method claiming to be simpler than the other. However, all these methods are time consuming although these are valid for any kind of profile.…”

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

“…1) the threshold current density increases, which can lead to induced thermal runaway that will destroy the device; 2 ) the power output decreases rapidly with increasing temperature [8] ; 3) the emitted wavelength changes by approximately 2.8 a/"C for a reflection feedback laser, and by 0.7 a/"c for a 0733-8724/84/0400-0175$01.00 0 1984 IEEE…”

“…Of the approximate techniques, the variational method used by Hotate and Okoshi [6] gives only an accuracy of the order of two percent in the calculation of the cutoff frequency. The perturbation method [ 7 ] , [8] gives good results only for profiles which deviate slightly from the unperturbed profile for which analytical solutions are known (generally step-or parabolicindex profiles). The integral-equation method developed by Kokubun et al [9] involves successive approximations and requires many numerical evaluations of double and triple integrals and is, therefore, of restricted applicability.…”

An Exact Analysis of the Fundamental and First Higher Order Mode in Graded Index Fibers with Direct Power Series Method

“…We have studied modal field distributions, Petermann-2 spot size, normalized propagation constants, cut-off frequencies for LP 01 -LP 11 modes. Earlier works on cut-off frequency calculations based on matrix method [18], perturbation method [19] and variational method [20], are compared with our approach. The calculation of cut-off frequency by PSM shown in this paper proves to be an exact method in comparison to earlier methods.…”