An optical waveguide structure includes a rotator having a dual-layer core. A first layer of the dual-layer core may include a tapering portion. A second layer of the dual-layer core may include a rib portion disposed on the tapering portion. The combination of the rib portion and the tapering portion may receive a pair of optical signals, one being polarized in a TE mode and the other being polarized in a TM mode, and convert them to a pair of TE mode optical signals.