Attenuation
Attenuation turns up in 2 fields: fiber optics, brewing. Here is what it means to the people in each one.
Attenuation in fiber optics
The gradual loss of optical power as light travels along a fiber, expressed in decibels.
Power lost along a fiber, mostly to Rayleigh scattering from tiny density variations frozen into the glass, plus absorption by impurities and bending. Scattering falls steeply as wavelength increases, so singlemode fiber loses less at 1550 nm than at 1310 nm, and multimode less at 1300 nm than at 850 nm. Total link attenuation adds fiber loss to connector and splice losses.
"Attenuation at 1550 is right where it should be, about 0.2 dB a kilometer, so the glass itself is fine."
Attenuation in brewing
The percentage of original sugars in a wort or must that yeast has converted into ethanol and carbon dioxide.
Brewers measure this by comparing the original specific gravity of the unfermented liquid against the final gravity after fermentation is complete. Apparent attenuation measures the simple drop in gravity using a hydrometer, while real attenuation accounts for the lower density of the newly created alcohol. Most standard ale yeasts achieve between sixty-five and eighty percent conversion.
"Check the gravity on tank four, we're looking for at least seventy-five percent apparent attenuation before we crash it."