Multimode fiber is designed to operate at 850 and 1300 nm, while singlemode fiber is optimized for 1310 and 1550 nm. The difference between 1300 nm and 1310 nm is simply a matter of convention, harking back to the days when AT&T dictated most fiber optic jargon. Why do we use the infrared? Because the attenuation of the fiber is much less at those wavelengths. The attenuation of glass optical fiber. That value determines whether the module is designed for multimode fiber (MMF) or single-mode fiber (SMF), how much attenuation the signal will experience, how dispersion behaves over distance, and whether optical amplification or DWDM systems are possible. Choosing the wrong wavelength can result. This article delves into why 850, 1310, and 1550 nm are standard, what less-known regimes and tradeoffs exist, and how an OEM fiber-cable manufacturer can design and test with wavelength considerations built in. Invest in dispersion management tools to maintain high data rates and clear. Single mode fiber optic cable is made up of a small diameter glass or plastic core surrounded by cladding, which is a layer of reflective material. This small diameter core, typically around 9 microns in diameter, allows only one mode of light to pass through, resulting in a narrower beam of light. Multimode fiber (MMF) is a kind of optical fiber mostly used in communication over short distances, for example, inside a building or for the campus.