Low-noise and high-gain 1.58 µm bandEr ³⁺ -doped fibre amplifiers with cascadeconfigurations

The authors constructed two low-noise and high-gain 1.58 µm band Er3+-doped fibre amplifiers (EDFAs) with cascade configurations. One consisted of 0.98 and 1.48 µm band pumped silica-based Er3+-doped fibre amplifier units as first and second units, exhibiting a noise figure of 5.0 dB and a signal gain of 32.8 dB for a 1.58 µm band WDM signal. The other employed a fluoride-based Er3+-doped fibre amplifier unit as a second unit and exhibited a noise figure of 5.1 dB and a signal gain of 25.0 dB. Both EDFAs had low-noise and high-gain characteristics.