One example relates to an optical engine comprising a given layer of given material overlaying an optical waveguide of another material. The given layer of given material can comprise an aligning seat to receive an optical transmitter to provide the optical signal. The aligning seat can also align the optical transmitter such that the optical transmitter provides the optical signal in a direction that is substantially non-oblique relative to a longitudinal axis of the optical waveguide. The optical engine can also include an optical signal redirector to tilt the optical signal by a tilt angle. The optical waveguide can comprise a grating coupler to diffract the optical signal provided at the tilt angle into the optical waveguide.
