640 Gbit/s format conversion of RZ-OOK to NRZ-OOK has been numerically demonstrated with a specially-apodized linearly-chirped fiber Bragg grating in transmission. The spectral response of the Bragg grating is designed according to the optical spectra of the algebraic difference between RZ-OOK and NRZ-OOK signal.
We present a scheme for on-chip optical mode conversion in a hybrid photonic-phononic waveguide. Both
propagating optical and acoustic wave can be tightly confined in the hybrid waveguide, and the acoustooptical
interaction can be enhanced to realize optical mode conversion within a chip-scale size. The
theoretical model of the acousto-optic interaction is established to explain the mode conversion. The
numerical simulation results indicate that the high efficient mode conversion can be achieved by adjusting
the intensity of the acoustic wave. We also show that the mode conversion bandwidth can be dramatically
broadened to 13 THz by adjusting the frequency of the acoustic wave to match phase condition of the
acousto-optic interaction. This mode converter on-chip is promising in order to increase the capacity of
silicon data busses for on-chip optical interconnections.