Optical data transmission at 44Tb/s and 10 bits/s/Hz spectral density
over standard fibre with a single micro-comb source chip
Abstract
Micro-combs - optical frequency combs generated by integrated
micro-cavity resonators – offer the full potential of their bulk
counterparts, but in an integrated footprint. The discovery of temporal
soliton states (DKS – dissipative Kerr solitons) as a means of
mode-locking micro-combs has enabled breakthroughs in many fields
including spectroscopy, microwave photonics, frequency synthesis,
optical ranging, quantum sources, metrology and more. One of their most
promising applications has been optical fibre communications where they
have enabled massively parallel ultrahigh capacity multiplexed data
transmission. Here, by using a new and powerful class of
micro-comb called “soliton crystals”, we achieve unprecedented data
transmission over standard optical fibre using a single integrated chip
source. We demonstrate a line rate of 44.2 Terabits per second (Tb/s)
using the telecommunications C-band at 1550nm with a spectral efficiency
– a critically important performance metric - of 10.4 bits/s/Hz.
Soliton crystals exhibit robust and stable generation and operation as
well as a high intrinsic efficiency that, together with a low soliton
micro-comb spacing of 48.9 GHz enable the use of a very high coherent
data modulation format of 64 QAM (quadrature amplitude modulated). We
demonstrate error free transmission over 75 km of standard optical fibre
in the laboratory as well as in a field trial over an installed
metropolitan optical fibre network. These experiments were greatly aided
by the ability of the soliton crystals to operate without stabilization
or feedback control. This work demonstrates the capability of optical
soliton crystal micro-combs to perform in demanding and practical
optical communications networks.