Optical power margin

Optical power margin: In an optical communications link, the difference between (a) the optical power that is launched by a given transmitter into the fiber, less transmission losses from all causes, and (b) the minimum optical power that is required by the receiver for a specified level of performance.

Note 1: The optical power margin is usually expressed in dB. At least several dB of optical power margin should be included in the optical power budget.

Note 2: The amount of optical power launched into a given fiber by a given transmitter depends on the nature of its active optical source[?] (LED or laser diode) and the type of fiber, including such parameters as core diameter[?] and numerical aperture. Contrast with optical power budget.

Source: from Federal Standard 1037C