A multi-band hybrid amplifier is disclosed for use in optical fiber
systems. The amplifier uses Raman laser pumps and semiconductor optical
amplifiers in series to produce a relatively level gain across the
frequency range of interest. Multiple Raman pumps are multiplexed before
coupling into the fiber. The Raman amplified optical signal may be
demultiplexed and separately amplified by the SOAs before
re-multiplexing. Gain profiles of the Raman pumps and the SOAs are
selected to compensate for gain tilt and to alleviate the power penalty
due to cross-gain modulation in the SOAs. The disclosed hybrid amplifier
is especially useful in coarse wavelength division multiplexing (CWDM)
systems.