Comment on "Demonstration of net gain at 1550 nm in an erbium-doped polymer single mode rib waveguide"Integrated waveguide amplifiers based on high concentration Er 3+ doped BaY 2 F 8 crystals are numerically studied by combining a full-vectorial finite element based modal analysis and propagation-rate equations. Using realistic input data, such as the absorption/emission cross sections and Er level lifetimes measured on grown crystal samples, we investigate the amplifier performance by optimizing the total Er concentration. We predict optimum gain coefficient up to 5 dB/ cm and broad amplification bandwidth exceeding 80 nm with 1480 nm pumping.