Waves can have the same mode but have different frequencies. This is the case in single-mode fibers, where we can have waves with different frequencies, but of the same mode, which means that they are distributed in space in the same way, and that gives us a single ray of light.OverviewIn, a single-mode optical fiber, also known as fundamental- or mono-mode, is an designed to carry only a single of light - the. Modes are the possible solutions o. In 1961, while working at American Optical published a comprehensive theoretical description of single mode fibers in the. At the Corn. Unlike, single-mode fiber does not exhibit. This is due to the fiber having such a small cross section that only the first mode is transported. Single-mode fibers are therefore b.