Abstract
We review the use of optical frequency combs in wavelength-division multiplexed (WDM) fiber optic communication systems. In particular, we focus on the unique possibilities that are opened up by the stability of the comb-line spacing and the phase coherence between the lines. We give an overview of different techniques for the generation of optical frequency combs and review their use in WDM systems. We discuss the benefits of the stable line spacing of frequency combs for creating densely-packed optical superchannels with high spectral efficiency. Additionally, we discuss practical considerations when implementing frequency-comb-based transmitters. Furthermore, we describe several techniques for comb-based superchannel receivers that enables the phase coherence between the lines to be used to simplify or increase the performance of the digital carrier recovery. The first set of receiver techniques is based on comb-regeneration from optical pilot tones, enabling low-overhead self-homodyne detection. The second set of techniques takes advantage of the phase coherence by sharing phase information between the channels through joint digital signal processing (DSP) schemes. This enables a lower DSP complexity or a higher phase-noise tolerance.
Highlights
The advent of the erbium-doped fiber amplifier (EDFA) in the late 1980s [1,2] transformed fiber optic communications in two profound ways
The lines need to display a high optical signal-to-noise ratio (OSNR) (>30 dB), a spacing in the order of 10–100 GHz, optical linewidths
A few years later, it was recognized that optical frequency combs, those based on EO comb technology, could be very attractive as wavelength-division multiplexed (WDM) sources
Summary
The advent of the erbium-doped fiber amplifier (EDFA) in the late 1980s [1,2] transformed fiber optic communications in two profound ways. The first demonstrations of amplified WDM data transmission came in 1990 [3,4] and were followed by massive commercial installations of WDM systems during the second half of the 1990s [5]. These developments paved the way for affordable worldwide telecommunications, and the Internet, as we know it today. In this paper we will review the work on using optical frequency combs for WDM transmission and put particular emphasis on discussing the unique benefits that are enabled by the use of frequency combs in contrast to discrete lasers. We will briefly outline the unique possibilities that combs enable in optical communications, as well as provide an overview for the remaining sections of this article
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