A leaky mode or tunneling mode in an optical fiber or other waveguide is a mode having an electric field that decays monotonically for a finite distance in the transverse direction but becomes oscillatory everywhere beyond that finite distance. Such a mode gradually "leaks" out of the waveguide as it travels down it, producing attenuation even if the waveguide is perfect in every respect. In order for a leaky mode to be definable as a mode, the relative amplitude of the oscillatory part (the leakage rate) must be sufficiently small that the mode substantially maintains its shape as it decays.
Leaky modes correspond to leaky rays in the terminology of geometric optics. The propagation of light through optical fibre can take place via meridional rays or skew rays. These skew rays suffer only partial reflection while meridional rays are completely guided. Thus the modes allowing propagation of skew rays are called leaky modes. Some optical power is lost into clad due to these modes.
Famous quotes containing the words leaky and/or mode:
“A leaky faucet, a barking dog—those are things you tolerate.”
—Candace Gingrich (b. c. 1967)
“The mode of clearing and planting is to fell the trees, and burn once what will burn, then cut them up into suitable lengths, roll into heaps, and burn again; then, with a hoe, plant potatoes where you can come at the ground between the stumps and charred logs; for a first crop the ashes suffice for manure, and no hoeing being necessary the first year. In the fall, cut, roll, and burn again, and so on, till the land is cleared; and soon it is ready for grain, and to be laid down.”
—Henry David Thoreau (1817–1862)