Single fiber modules (BiDi) use one fiber for both transmitting and receiving data. They are easier to set up and give steady communication. They use a thin fiber. In fiber-optic communication, a single-mode optical fiber, also known as fundamental- or mono-mode, is an optical fiber designed to carry only a single mode of light - the transverse mode. Modes are the possible solutions of the Helmholtz equation for waves, which is obtained by combining. A single strand of glass fiber, called single-mode fiber, is used to transmit single-mode or light beams. It can transmit higher bandwidth than multimode fiber but requires a light source with a limited spectral range. It works best for short distances.