Multistage optical amplifier with Raman and EDFA stages

摘要

The present invention provides an optical amplifier for a wavelength division multiplexed communication system, including a first amplifier stage responsive to changes in gain to cause a wavelength dependent gain tilt in one direction. a second amplifier stage (3) responsive to corresponding changes in gain to cause a wavelength dependent gain tilt in an opposite direction and gain control means (4) for controlling the gain of the first (2) and second (3) amplifier stages to maintain a substantially flat response for the amplifier (1) over time, in which the first amplifier stage (2) is a length of optical transmission fibre providing a Raman amplifier. The present invention provides an optical amplifier which uses dynamic gain tilt adjustment whilst maintaining a constant output level from the amplifier.