This glossary has been developed specifically to aid the reader of this volume in interpreting unfamiliar terms. The definitions are intended to have a practical, rather than formal, presentation. That is, they may be specifically oriented toward the use of the word in the telecommunications or electro-optics sciences rather than a more general definition that would be found in a generic encyclopedia or dictionary.

Numbers & Symbols

rad

Microradian, a millionth of a radian.

W

Microwatt, a millionths of a watt.

1000BaseT

A terabit per second over a twisted pair, per Ethernet Standard IEEE802.3ab.

A

aberrated

Defines specific degradations in image quality. Aberrations include, but are not limited to, field curvature, distortion, coma, chromatic aberration, and astigmatism.

absorptance

The property of a material to that acts to reduce the amount of radiation traversing through a section of the material. It is measured as the fraction of radiation absorbed traversing the material. Generally, the bulk absorptance of radiation by a material follows Beer's law.

acceptance angle

The half angle of the acceptance cone, this is the angle (or less) in which light will be easily coupled into a fiber.

adaptive optics

Optical subsystems with the capability to change the wavefront in real time.

ADM

Add-drop multiplexer.

ADSL

Asymmetric digital subscriber line.

afocal

Describes an optical system that does not form a focus, such as often employed in astronomical telescopes and in laser beam expanders. Such optics accept a light field and produce an unfocused beam.

Airy disk

The distribution of...