Influence of a central depression on the dispersion characteristics of a graded-index profile

Ray-tracing techniques and modal relations are utilised for evaluating the dispersion characteristics of multimode fibres with a quasiparabolic profile having a central depression. The results show that the dispersion increases with the dimensions of the depression; however, such an increase may be negligible if the dimensions of the depression approach those corresponding to realistic preforms produced by the c.v.d. technique.