Quick answer: Single-mode fiber has a 9-micrometer core, carries light in one path, and supports distances up to 80+ km. Single-mode and multimode are the two fundamental types of fiber optic cable, and they are not interchangeable. This guide breaks down exactly how they differ, when to use each, and. Two main types dominate network design: multimode fiber and single-mode fiber. While they may look similar from the outside, they differ significantly in core size, transmission behavior, distance capability, bandwidth potential, equipment requirements, and overall cost.