Pronounced "ruh-mahn," it is a device that boosts the signal in an optical fiber by transferring energy from a powerful pump beam to a weaker signal beam. It relies on the interaction between light and atoms in the fiber. Unlike erbium-doped fiber amplifiers (EDFAs), which boost wavelengths in the 1530-1610 nm range, a Raman amplifier can increase the signal strength of any wavelength by pumping at 13THz more than the desired frequency.

Normally, Raman amplification is distributed along lengths of signal-transmitting fiber. A Raman pump laser is typically stationed at the end of a fiber run and pumps backward several kilometers to amplify signals through that region. See EDFA.