Attenuation constant

In telecommunication, the term attenuation constant has the following meanings:

1. The real part of the propagation constant in any electromagnetic propagation medium.

Note 1: The attenuation constant is usually expressed as a numerical value per unit length.

Note 2: The attenuation constant may be calculated or experimentally determined for each medium.

2. For a particular propagation mode in an optical fiber, the real part of the axial propagation constant[?].

Source: from Federal Standard 1037C