Single-mode fiber can only transmit the following modes

Single-mode fiber can transmit only a single transverse mode of light, known as the fundamental mode.Single-mode optical fiber is designed with a very small core diameter, typically around 8 to 10 microns, which allows only one mode of light to propagate through the fiber . This mode is the fundamental transverse mode, meaning the electromagnetic oscillations of the light are perpendicular to the fiber axis, and the light travels in a single, well-defined path along the fiber .Key CharacteristicsCore Size: The small core prevents multiple modes from propagating, reducing modal dispersion and enabling long-distance, high-bandwidth transmission .Wavelengths: Single-mode fibers typically operate at wavelengths of 1310 nm or 1550 nm, which are optimal for minimal attenuation and long-distance communication .Applications: They are widely used in telecommunications, CATV, and high-speed data networks where signal integrity over long distances is critical .Comparison with Multimode FiberUnlike single-mode fiber, multimode fiber has a larger core (50–62.5 microns) and allows multiple light modes to propagate simultaneously, which can cause modal dispersion and limit transmission distance . Single-mode fiber's restriction to a single mode ensures lower signal loss and higher bandwidth, making it ideal for backbone and long-haul networks. In summary, single-mode fiber transmits only the fundamental transverse mode, providing high-speed, long-distance communication with minimal signal degradation .