Fiber optic transmission uses different wavelengths of light to carry digital data. The three main wavelengths used for fiber optic transmission are 850, 1300, and 1550 nanometers. Multi-mode glass fibers use light at 850 nm - 1300nm, referred to as “short wavelength,”. In contrast, single-mode fiber operates at 1310 or 1550 nm, called “long wavelength.