Package substrates for optical die structures are generally described. In one example, an apparatus includes a package substrate having one or more plated through hole (PTH) structures, an optical waveguide coupled with the package substrate, the optical waveguide having one or more input/output (I/O) optical signal pathways to route I/O signals to and from the package substrate, and one or more optical fibers coupled with the optical waveguide, the one or more optical fibers being disposed in the PTH structures to route I/O signals to and from a motherboard.