Fiber-optic amplifier with feedback-insensitive pump laser

Abstract

Prior art fiber-optic amplifiers which are used in a fiber-optic link to amplify the light signals to be transmitted have the disadvantage that the semiconductor lasers employed as pump lasers are highly sensitive to feedback, so that the stability of the light-signal transmission is impaired by pump light reflected back into the pump lasers. According to the invention, the operating current for such pump lasers (4) contains a noise current, so that the pump laser emits its pump light in many modes, which makes it insensitive to feedback. To prevent the noise component of the pump light which is caused by the noise current from affecting the amplification of the light signals to be transmitted, the noise current is filtered in such a way that its spectral components have frequencies which lie above the reciprocal lifetime of that energy level of the active laser medium which causes the amplification of the light signals.

Dependencies are inferred from the claim text.