A novel technique is proposed to increase the effective index difference ( Δ n eff ) between higher order modes of a multimode step-index fiber. Multimode fibers provide a higher effective area and their higher order modes are also resistant to area reduction due to bending. However, the larger effective area comes with an increased number of modes which are more prone to mode coupling and mode mixing. The modal stability is directly related to the effective index difference between the mode of propagation and its neighboring modes. We have shown here that the modal stability between LP 06 mode and its neighboring antisymmetric LP 15 and LP 16 modes can be increased more than 54% by the introduction of air-holes array along the circumference of the fiber. We have also shown variation in the effective index difference with possible fabrication tolerances that may occur in air-holes size and change in their locations. Furthermore, the technique presented here can also be applied to increase the stability of other higher modes of a multimode fiber.
