Almost all fibers used today are single strands.
Fiber bundles find use primarily in coherent and image transmitting optical systems.
There are also plastic fibers for inexpensive, short distance transmission. The basic design of an optical fiber consists of two components - the core and the cladding. Core and cladding differ primarily in the refractive index of the glass. The core's refractive index is slightly higher than the cladding's, thereby creating a boundary for a circular waveguide. Fiber optic signaling in data transmission is increasingly being used in high-density applications.