Flattening the gain spectrum of an erbium-dopedfibre amplifierby connecting an Er ³⁺ -doped SiO ₂ -Al ₂ O ₃ fibreand an Er ³⁺ -doped multicomponent fibre

A technique is proposed for designing the gain spectrum in Er3+-doped fibre amplifiers. It uses an active fibre constructed by connecting two erbium-doped fibres with different host materials. An Er3+-doped SiO2-Al2O3 fibre and an Er3+-doped multicomponent fibre were connected to flatten the gain spectrum in the 1.55 µm band. A flat gain spectrum was achieved in the 1.543–1.558 µm bandwidth range with a signal gain of 26 dB and a noise figure of less than 6 dB.