Fiberoptic collimators come in many forms. They can be singlemode or multimode. Their diameters can be as small as the fiber itself, for example 125 um, or as large as tens or hundreds of millimeters. Their basic structure, however, consists of a lens and an optical fiber. In this tutorial we will explore the many faces of "simple" fiberoptic collimators.

LENS TYPE: Almost all known lens types have been used to construct fiber optic collimators. These lenses include fiber lenses, ball lenses, aspherical lenses, spherical singlets and doublets, GRIN (GRaded INdex) lenses, microscope objectives, cylindrical lenses, no lens at all as in the case of thermally expanded core (TEC) fiber. Lens materials can vary from glass to plastic to silicon. By a large margin, most of the fiber optic collimators used today are made using GRIN lenses. GRIN lenses are small, easy to handle, relatively low cost, and competitive in optical performance. They do have limitations though. GRIN lenses rarely come in large size and their performance is marginal in the visible spectrum range.