US Patent 7911684 Variable gain erbium doped fiber amplifier

Systems, methods, and apparatuses are provided for variable gain optical fiber amplifiers. In one implementation, a variable gain optical amplifier is provided. The amplifier includes a first erbium doped fiber configured to receive an input optical signal, a second erbium doped fiber configured to output an output optical signal, a gain flattening filter positioned between the first erbium doped fiber and the second erbium doped fiber, a pump laser configured to provide energy to the first erbium doped fiber and the second erbium doped fiber, a thermo electric cooler configured to control a temperature of one or more of the first erbium doped fiber and the second erbium doped fiber, and a controller configured to adjust an output from the pump laser and a temperature of at least one of the first erbium doped fiber and the second erbium doped fiber to provide a variable flat spectral gain output.