Transmitter Bandwidth Extension using Optical Time-Interleaving Modulator and Digital Spectral Weaver

We generate 150-Gbaud QAM signals by using an optical time-interleaving modulator driven with 38.1-GHz-bandwidth sub-signals. A digital spectral weaver enables generation of arbitrary bandwidth-extended signals with a simple filter-less optical configuration.

1. Introduction

To meet ever-growing demand for high-speed data communications services, high-modulation-order and high-symbol-rate transmission technologies are extensively studied [1]. High-speed digital-to-analog converters (DACs) are indispensable to generate high-modulation-order signals, but their analog bandwidths are the major factors that restrict the achievable symbol rate. Since DACs’ analog bandwidths are not expected to scale drastically, bandwidth-extension technologies using parallel DAC architectures with additional analog electronics are attracting a lot of attention [1]-[3]. On the other hand, bandwidth extension can also be achieved in the optical domain [4], [5]. Although the optical approaches require higher hardware complexities, they are less challenging in terms of scaling the final output bandwidth. The combination of the electronic and optical syntheses will also be promising.