An optical waveguide for optical interconnection including a polymer sheet comprising a crosslinked product of a prepolymer, the prepolymer prepared by condensation reaction between a first compound represented by the formula Ar—H, where Ar comprises (a) a crosslinkable moiety at one end, (b) a moiety selected from the group consisting of —O—, —S—, —COO—, —CO—, —COS—, —SO2—, and —NH—, and (c) one or two repeating units selected from the group consisting of: where A is carbon or nitrogen, and X is hydrogen or halogen; and a second compound consisting of an aromatic moiety.