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The layout of folded spiral erbium-doped planar waveguide optical amplifiers (EDWAs) is considered. A quasi-continuous function to describe the curvature of a folded-spiral layout is presented, based upon the use of cosine and raised-cosine variations in bend curvature. This layout provides greater gain in a given area than the corresponding fixed-radii layout. Analysis is initially based on simple geometric principles and the reduction of bending losses for 180° waveguide bends. Fold-back bends and complete EDWA layouts are then considered. Simulations are carried out using an algorithm that combines five-level rate equations with propagation by the method of lines.