Single mode fiber, short as SMF, is a fiber cable that only allows one mode of light to transmit. These feature a small modal dispersion for vast-distance signal transmission. Although they can do the same job in some instances, the different construction methods make each of them better suited to certain tasks and budgets. Typically, this fiber includes a small light-carrying core of about 9µm diameter. Q1: What distinguishes single mode fiber from multimode fiber? Q2: Can I connect single mode. But not all fiber cables are created equal: multimode (MM) and single mode (SM) fibers are the two primary types, each engineered for specific use cases, from short-range data center connections to transcontinental telecom backbones.