title: Optimally coherent Kerr combs generated with crystalline whispering gallery mode resonators for ultrahigh capacity fiber communications.
abstract: Optical Kerr frequency combs are known to be effective coherent multiwavelength sources for ultrahigh capacity fiber communications. These combs are the frequency-domain counterparts of a wide variety of spatiotemporal dissipative structures, such as cavity solitons, chaos, or Turing patterns (rolls). In this Letter, we demonstrate that Turing patterns, which correspond to the so-called primary combs in the spectral domain, are optimally coherent in the sense that for the same pump power they provide the most robust carriers for coherent data transmission in fiber communications using advanced modulation formats. Our model is based on a stochastic Lugiato-Lefever equation which accounts for laser pump frequency jitter and amplified spontaneous emission noise induced by the erbium-doped fiber amplifier. Using crystalline whispering-gallery-mode resonators with quality factor Q∼10^{9} for the comb generation, we show that when the noise is accounted for, the coherence of a primary comb is significantly higher than the coherence of their solitonic or chaotic counterparts for the same pump power. In order to confirm this theoretical finding, we perform an optical fiber transmission experiment using advanced modulation formats, and we show that the coherence of the primary comb is high enough to enable data transmission of up to 144  Gbit/s per comb line, the highest value achieved with a Kerr comb so far. This performance evidences that compact crystalline photonic systems have the potential to play a key role in a new generation of coherent fiber communication networks, alongside fully integrated systems.
authors: Institute of Photonics and Quantum Electronics (IPQ), Karlsruhe Institute of Technology (KIT), 76131 Karlsruhe, Germany.|Institute of Microstructure Technology (IMT), Karlsruhe Institute of Technology (KIT), 76131 Karlsruhe, Germany.
authors: Joerg
authors: J
authors: Pfeifle
authors: FEMTO-ST Institute (CNRS UMR6174), Optics Department, 15B Avenue des Montboucons, 25030 Besançon cedex, France.
authors: Aurélien
authors: A
authors: Coillet
authors: FEMTO-ST Institute (CNRS UMR6174), Optics Department, 15B Avenue des Montboucons, 25030 Besançon cedex, France.
authors: Rémi
authors: R
authors: Henriet
authors: FEMTO-ST Institute (CNRS UMR6174), Optics Department, 15B Avenue des Montboucons, 25030 Besançon cedex, France.
authors: Khaldoun
authors: K
authors: Saleh
authors: Institute of Photonics and Quantum Electronics (IPQ), Karlsruhe Institute of Technology (KIT), 76131 Karlsruhe, Germany.
authors: Philipp
authors: P
authors: Schindler
authors: Institute of Photonics and Quantum Electronics (IPQ), Karlsruhe Institute of Technology (KIT), 76131 Karlsruhe, Germany.
authors: Claudius
authors: C
authors: Weimann
authors: Institute of Photonics and Quantum Electronics (IPQ), Karlsruhe Institute of Technology (KIT), 76131 Karlsruhe, Germany.|Institute of Microstructure Technology (IMT), Karlsruhe Institute of Technology (KIT), 76131 Karlsruhe, Germany.
authors: Wolfgang
authors: W
authors: Freude
authors: FEMTO-ST Institute (CNRS UMR6174), Optics Department, 15B Avenue des Montboucons, 25030 Besançon cedex, France.
authors: Irina V
authors: IV
authors: Balakireva
authors: FEMTO-ST Institute (CNRS UMR6174), Optics Department, 15B Avenue des Montboucons, 25030 Besançon cedex, France.
authors: Laurent
authors: L
authors: Larger
authors: Institute of Photonics and Quantum Electronics (IPQ), Karlsruhe Institute of Technology (KIT), 76131 Karlsruhe, Germany.|Institute of Microstructure Technology (IMT), Karlsruhe Institute of Technology (KIT), 76131 Karlsruhe, Germany.
authors: Christian
authors: C
authors: Koos
authors: FEMTO-ST Institute (CNRS UMR6174), Optics Department, 15B Avenue des Montboucons, 25030 Besançon cedex, France.
authors: Yanne K
authors: YK
authors: Chembo