Analysis of mode approximations for predicting accurate fibre grating characteristics

A suitable set of coupled power and phase equations with initial value boundary conditions have been developed to calculate the characteristics of reflective fibre gratings. Because it is not necessary to use an iteration process, the calculations are much simplified for predicting the characteristics of linear fibre grating and nonlinear fibre grating devices. At the same time, we point out that in such calculations, much greater care must be exercised in the use of mode parameter approximations