Narrow-band fiber Raman optical amplifier

The invention refers to an optical Raman fiber amplifier (20), with an amplification fiber, wherein at least one section thereof has a ratio of Raman gain coefficient g R to Brillouin g B gain coefficient of g R Ig B larger than 0.001 at the fiber operating temperature and a vacuum wavelength of 1064 nm. The invention further refers to a corresponding light source, the use of a fiber and a method of amplifying light.