In most fiber optic systems, optical fiber and waveguides are coupled to and from bulk optical devices, creating hybrid optical devices. In this tutorial article, the authors explain in detail how to successfully collimate, focus, and align hybrid optics, including polarizing and polarization maintaining optics.

Glossary
Mode field diameter (MFD): A measure of the intensity profile of light traveling within a fiber. In Gaussian optics, this diameter is measured at the point where the light intensity drops to 13.5% (1/e2) of the peak intensity. In single-mode fibers, it is typically about 15% larger than the actual core size.

Numerical Aperture (NA): A measure of the maximum angle at which a given optical system can receive light. If a system can receive light within a cone having a half angle q, then the NA of that system is equal to sin q.