Insertion Loss and Misalignment Tolerance in Multimode Tapered Waveguide Bends

Experimental measurements of laterally tapered multimode waveguide bends fabricated photolithographically on FR4 printed circuit board establish that the product of the mean insertion loss (in linear units) and the mean source misalignment tolerance is a constant which depends only on the taper ratio TR (input width/output width) and not on the radius of curvature $R$. The minimum loss of 0.78 dB occurs in the special case of TR $=0.8$ , $R=14$ mm. Together, these form waveguide layout design rules for board-to-board and chip-to-chip optical interconnects.