Optimal design of cascaded long-period waveguide grating equalizer for broadband Er-Yb co-doped phosphate glass waveguide amplifiers

Broadband integrated Er-Yb codoped phosphate glass waveguide amplifier based on cascaded long-period waveguide grating gain-equalizer is proposed. The proposed cascaded long-period waveguide grating gain-equalizer consists of some different long-period waveguide grating filtering unit cells, and each cell can suppress certain peak gain at a specific wavelength. The intrinsical gain spectrum of amplifier is obtained by solving a set of rate and power propagation equations with overlapping integral-Runge Kutter method. The effect of the transmission spectrum of the proposed cascaded long-period waveguide grating on the flattening gain of Er-Yb codoped phosphate glass waveguide amplifier is discussed. The transmission function of the cascaded long-period waveguide grating filter is obtained.