The invention relates to an asymmetric Mach Zehnder Interferometer (MZI) having a reduced drive voltage, coupled to a compact low-loss arrayed waveguide grating (AWG) to provide a broader passband with low ripple. The integrated device has a compact stackable design for improved manufacturing yield. Inputs and outputs of the device are disposed in alignment on opposite sides of a silicon chip with the MZI having an opposite curvature to the AWG. To achieve this alignment, waveguide arms of the MZI are crossed without coupling between them before the optical signal is combined and coupled into the AWG.