In fiber optics, the mode field diameter (MFD) is an expression of distribution of the irradiance, i.e., the optical power per unit area, across the end face of a single-mode fiber.
For a Gaussian intensity (i.e. power density, W/m2) distribution in a single-mode optical fiber, the mode field diameter is that at which the electric and magnetic field strengths are reduced to 1/e of their maximum values, i.e., the diameter at which power density is reduced to 1/e2 of the maximum power density, because the power density is proportional to the square of the field strength.
Famous quotes containing the words mode and/or field:
“Curiously enough, it seems to be only in describing a mode of language which does not mean what it says that one can actually say what one means.”
—Paul Deman (1919–1983)
“The field of the poor may yield much food, but it is swept away through injustice.”
—Bible: Hebrew, Proverbs 13:23.