A new and effective method for the electromagnetic analysis of generic bent dielectric waveguides is presented. The method is based on the expansion of the bend mode in modes of the straight waveguide and permits determination of the shape and the phase constant of the fundamental mode of the bend waveguide with great accuracy at a very low computational cost. Simple analytical expressions of the phase constant, coupling losses, and bending-induced birefringence are derived under very general conditions. The proposed method is useful for the design and optimization of each bent section of integrated optics components.
Andrea Melloni, Federico Carniel, Raffaella Costa, and Mario Martinelli, "Determination of Bend Mode Characteristics in Dielectric Waveguides," J. Lightwave Technol. 19, 571- (2001)