Newsroom
What is Cut-off Wavelength?
Cut-off Wavelength is the wavelength below or above which an optical fiber changes its mode propagation behavior. In a single-mode fiber, it is the wavelength above which only the fundamental mode can propagate, while shorter wavelengths may allow additional modes to propagate.
It is an important parameter for determining whether a fiber will operate in single-mode or multimode conditions at a given wavelength.
HOW Cut-off Wavelength Works
Cut-off wavelength defines the transition between different mode propagation regimes in an optical fiber. It depends on the fiber's geometry and refractive-index profile, and therefore determines the wavelengths at which higher-order modes can no longer propagate.
Mode propagation
An optical fiber can support one or several guided modes depending on its design and operating wavelength.
Higher-order mode cut-off
As the wavelength increases, higher-order modes become unable to remain guided and disappear from propagation at their respective cut-off wavelengths.
Single-mode operation
Above the cut-off wavelength of the first higher-order mode, only the fundamental mode remains guided, enabling single-mode operation.
