All-optical wavelet-based orthogonal frequency division multiplexing system based on silicon photonic integrated components

In this study, the authors discuss in detail the implementation of all-optical orthogonal frequency-division multiplexing system based on discrete wavelet packet transform (DWPT) by using silicon-on-insulator (SOI) cascaded Mach-Zehnder interferometers (MZIs). DWPT can be used in the multiplexing and de-multiplexing of data channels in coherent optical communication in order to improve spectral efficiency excluding a cyclic prefix. DWPT and inverse-DWPT may be realised in an integrated-photonic MZI platform. They demonstrated experimentally the post-fabrication tuning of 1 x 4 cascaded MZI de-multiplexing filters. Tuning procedures effectively overcome fabrication tolerances and meet the target transfer function of the devices. The fabrication platform represents an essential stepping-stone toward the all-optical realisation of DWPT-based multiplexing.