In multimode fiber, the core diameter (50µm or 62. 5µm) is significantly larger than the wavelength of light (typically 850nm or 1300nm). This dimensional relationship permits multiple distinct light paths, or modes, to propagate simultaneously through the fiber. Whichever mode we are dealing with, it can either transit us to a multimode propagation or to a single-mode transience. Miller, "Communications Expands its Space", Nature Photonics, vol. 5-8, January 2017 (Invited Paper). Different propagation modes have different propagation velocities and phases, resulting in time delay and widening of.