Patent ID: 7643758

Claim:
An arrangement, the arrangement being arranged to add gain to a set of optical signals, the set of signals including a first band and a second band, the second band including signals of longer wavelengths than signals of the first band, the arrangement comprising: a multiplexer, the multiplexer being arranged to multiplex the set of signals; a first semiconductor optical amplifier, the first semiconductor optical amplifier having a first gain peak at a wavelength within the first band and an attenuation region for wavelengths at or longer than the wavelengths within an upper half portion of the second band, the first semiconductor optical amplifier being arranged to receive the set of signals from the multiplexer and to provide amplification to the signals within the first band and attenuation to the signals within the attenuation region; a second semiconductor optical amplifier, the second semiconductor optical amplifier having a second gain peak at a wavelength within the second band, the second semiconductor optical amplifier being arranged to receive the second band after the set of signals is processed by the first optical amplifier and to provide amplification to the second band; and a processing arrangement, the processing arrangement being arranged to pass the second band from the first semiconductor optical amplifier to the second semiconductor optical amplifier, the processing arrangement further being arranged to substantially prevent the first band from passing from the first semiconductor optical amplifier to the second semiconductor optical amplifier.