Modal dispersion characteristics of LP0m modes in a step-index multimode fiber

Abstract

A modal interferometer method (MIM) is applied to measure the differential mode delay (DMD) between the L P 0 m modes traversing a step-index multimode fiber (SI-MMF). Only linearly polarized radial modes, i.e.,  L P 0 m modes, are excited and transmitted in the SI-MMF by using a single-mode-multimode-single-mode (SMS) fiber structure. The measurement principle is based on investigating a transmitted spectrum through temporal decomposition by means of a Fourier transform. The Fourier-transform-based MIM provides simultaneous measurements of the DMD between the L P 0 m modes. The wavelength dependence of the DMD is estimated experimentally in both the 1260–1360 nm and 1450–1625 nm telecommunication bands. The normalized frequency dependence of the DMD is also investigated theoretically. The result suggests that the 1260–1360 nm band is preferable to the 1450–1625 nm band for a mode-division multiplexing (MDM) transmission employing an SI-MMF in terms of realizing a smaller DMD.