The wavelength of single-mode fiber is

Single-mode optical fibers typically operate at wavelengths of 1310 nm and 1550 nm.Single-mode fiber (SMF) is designed to allow only one light mode to propagate, which minimizes dispersion and enables high-bandwidth, long-distance transmission. The standard core diameter is 8–10 µm, with a cladding diameter of 125 µm, which supports single-mode operation at these wavelengths .Standard Wavelengths1310 nm: Often used for shorter to medium distances, this wavelength has low dispersion and moderate attenuation, making it suitable for campus networks and metropolitan area networks .1550 nm: Preferred for long-distance transmission due to its lower attenuation and compatibility with optical amplifiers. It is widely used in backbone networks, DWDM systems, and long-haul telecommunications .Cut-Off WavelengthSingle-mode fibers have a cut-off wavelength, below which multiple modes can propagate. For standard fibers like Corning SMF-28, the cut-off is around 1260 nm, ensuring single-mode operation above this wavelength .Fiber TypesOS1: Indoor single-mode fiber, optimized for 1310 nm and 1550 nm, with maximum attenuation of 1 dB/km at 1310 nm and 0.4 dB/km at 1550 nm .OS2: Outdoor or long-haul fiber, optimized for 1550 nm, with lower attenuation and suitable for distances up to 200 km .SummarySingle-mode fibers are optimized for 1310 nm and 1550 nm wavelengths, providing low attenuation and high bandwidth for long-distance communication. The choice of wavelength depends on the application, distance, and network design, with 1310 nm used for shorter links and 1550 nm for long-haul or high-capacity networks .