Amplifiers in Multi–Band Scenarios—Output Power Requirements, Control and Performance Characteristics

Parallel data transmission in several wavelength bands over a single optical fiber imposes divergent requirements on the employed optical amplifiers. The focus of the investigations is on the maximum output power and the maximum gain each of the amplifiers needs to be designed for. The results for a C+L–band system reveal that the maximum output power provided by a long–wavelength band (L–band) amplifier is limited and any further increase of the total power launched into a fiber span needs to be realized by higher total powers in the conventional band (C–band). Based on these findings, the resulting noise performance is determined for operation at maximum number of channels for a typical design of a commercial erbium–doped fiber amplifier. Output power and gain requirements are finally considered when further extending the used bandwidth by the short–wavelength band (S–band). For this scenario, noise figure is determined by means of a generic optical amplifier model making the results independent of the current level of technology. It is shown that designing amplifiers for making the optical transmission system tolerant to power transients leads to noise figure degradation of the long–wavelength amplifiers when all bands are fully populated with channels.