Advanced Optical Modulation Formats

Fiber-optic communication systems form the high-capacity transport infrastructure that enables global broadband data services and advanced Internet applications. The desire for higher per-fiber transport capacities and, at the same time, the drive for lower costs per end-to-end transmitted information bit has led to optically-routed networks with high spectral efficiencies. Among other enabling technologies, advanced optical modulation formats have become key to the design of modern wavelength-division multiplexed (WDM) fiber systems. In this paper, we review optical modulation formats in the broader context of optically-routed WDM networks. We discuss the generation and detection of multi-Gigabit/s intensity- and phase-modulated formats; we highlight their resilience to key impairments found in optical networking, such as optical amplifier noise, multi-path interference, chromatic dispersion, polarization-mode dispersion, WDM crosstalk, concatenated optical filtering, and fiber nonlinearity.