Definitions for "Singlemode Fiber"
The core in a singlemode fiber has a diameter of 3-10m. supports only one mode of light propagation above the cutoff wavelength, hence the name. The number of modes supported by the fiber is determined by the size and composition of the materials used, and the wavelength of light transmitted down the fiber.
A fiber with a small core, only a few times the wavelength of light transmitted, that only allows one mode of light to propagate. Commonly used with laser sources for high speed, long distance links.
An optical waveguide in which only the lowest-order bound mode, which may consist of a pair of orthogonally polarized fields, can optical propagate at the wavelength of interest.