Analog Electronic and Optical Multiplexing Techniques for Transmitter Bandwidth Extension

As fiber-optic transmission systems evolve toward higher per-wavelength-channel data rates, the analog bandwidth of digital-to-analog converters (DACs) has become a bottleneck. Here, external analog multiplexing techniques utilizing multiple DACs in each signaling dimension enable us to generate signals with bandwidths exceeding the DACs’ capabilities. This tutorial provides a comprehensive review of these techniques, including electronic and optical ones. Moreover, it presents an analytical model from the perspective of spectral image superposition as a basis for a unified understanding of the principles of the various schemes.