In a cable or circuit, any extraneous signal which tends to interfere with the signal normally present in or passing through the system. Nanometer A billionth of a meter.
Nanometers are a unit of measurement for wavelengths in fiber-optic communications.
No return to zero. The sine of half the angle over which a fiber can accept light multiplied by the refractive index of the medium containing the light. It is a function of the relationship between the refractive index of the core and that of the cladding.