Abstract
Abstract Current fibre optic communication systems owe their high-capacity abilities to the wavelength-division multiplexing (WDM) technique, which combines data channels running on different wavelengths, and most often requires many individual lasers. Optical frequency combs, with equally spaced coherent comb lines derived from a single source, have recently emerged as a potential substitute for parallel lasers in WDM systems. Benefits include the stable spacing and broadband phase coherence of the comb lines, enabling improved spectral efficiency of transmission systems, as well as potential energy savings in the WDM transmitters. In this paper, we discuss the requirements to a frequency comb for use in a high-capacity optical communication system in terms of optical linewidth, per comb line power and optical carrier-to-noise ratio, and look at the scaling of a comb source for ultra-high capacity systems. Then, we review the latest advances of various chip-based optical frequency comb generation schemes and their applications in optical communications, including mode-locked laser combs, spectral broadening of frequency combs, microresonator-based Kerr frequency combs and electro-optic frequency combs.
Highlights
An optical frequency comb has an optical spectrum consisting of a series of discrete, spaced and phase-locked frequency lines
We have reviewed recent achievements in chip-based frequency combs designed for use in optical communications, including mode-locked laser combs, spectral broadening of frequency combs, microresonatorbased combs and EO-modulated frequency combs, and their applications in high-speed optical communication systems
Characteristics of frequency combs for optical communications include absolute frequencies and frequency spacing aligned with the ITU-grid, low optical linewidth on the order of 10 kHz, adequate power per comb line to carry data on the order of −30 to −10 dBm or more, spectral flatness allowing for equalized signal power across the telecom band in question, and high pump-to-comb conversion efficiency
Summary
An optical frequency comb has an optical spectrum consisting of a series of discrete, spaced and phase-locked frequency lines. Hansch for their pioneering work on optical frequency combs for spectroscopy applications. Current optical communication systems are based on wavelength-division multiplexing (WDM), which relies on arrays of discrete wavelength laser sources [17]. An optical frequency comb with a frequency spacing on the order of 10–100 GHz can be used to replace the laser lines from individual sources in a WDM communication system, and may potentially replace hundreds of individual lasers, with the aim of reducing the energy consumption and size of the transmitter [2, 5]. We will summarize all the frequency comb generation schemes mentioned in the paper and discuss the potentials and issues for implementing chip-based frequency combs in real high-capacity WDM optical communication systems
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