Can I mix Single Mode and Multimode fiber in the same link? Absolutely not. Because the core sizes are different (9 um vs 50 um), the light will not couple correctly. You will experience a loss of at least 18dB to 20dB, which will immediately crash the link. Multimode Fiber comparison, I will compare those two fiber optic cables, helping you learn the difference and determine which best suits your fiber cabling system. However, the specific choice of fiber wavelength will depend on the requirements of the. SMF (Single-Mode Fibers) is the fiber cable that is designed to carry only a single mode of light that is the transverse mode. Multimode fiber cables are the type of fiber cables that transmit data via their core of larger diameters. Two of the most common cable types you'll hear about when implementing a fiber network are single mode and multimode fiber.