Group delay in graded-index fibres with non-power-law refractive profiles

The group delay of modes in graded-index fibres is often calculated by the method of Gloge and Marcatili. This method can, however, yield misleading results if the refractive profile of a fibre does not strictly follow a power law of the radius, e.g. if it is close to the optimum profile, but has statistical distortions. The letter presents a new method for the calculation of group delay which has a simplicity similar to that of the Gloge¿Marcatili method and can be used in conjunction therewith as an easy way of finding reliable results for non-power-law refractive profiles.