In this talk, I will consider optical comb sources characterised by a certain bandwidth, comb line power and background noise level, and discuss requirements to such combs in order to qualify as sources in coherent optical communication systems. I will describe how, that for comb line powers and performances already achievable by integrated micro-ring resonators, a single comb source could act as a highly scalable multi-wavelength (WDM)-source for multi-Pbit/s spatially multiplexed (SDM) systems. I will discuss the possibilities of using a single comb source to support 10s Pbit/s data transmission, and how the scaling to capacities beyond that, is promising. I will discuss using a single comb source for ultra-long-haul transmission systems, such as trans-oceanic reaches of e.g. 8.000 km, and I will show how a comb source performs just as well as a bank of individual lasers, with the added benefit of the possibility to reduce the spectral guard-band, thus increasing the spectral efficiency.

Optical microresonators are attractive comb sources due to their small form factor and stable broad optical spectra. We report on the first demonstration of microcomb-based digital holography. The large line spacing of microcombs promises an unprecedented combination of precision, fast update rate and ambiguity ranges on the scale of a few mm. Using a pulse-driven lithium niobate microcomb of 100 GHz line spacing and a scanning Michelson interferometer, we generate spectral hypercubes of holograms. Our first experimental results show that the amplitude and phase information of the object can be recovered for more than 100 comb lines.

Self-injection locking to a photonic crystal ring-microresonator with synthetic back-reflection is demonstrated for the first time. The on-chip system permits deterministic generation of exclusively single-soliton microcombs and does not rely on random backscattering from defects or imperfections.

In this work, we present a theoretical and numerical study about the generation of double- frequency-comb-like source with Gain Through Filtering (GTF) in passive Polarization Maintaining (PM) fibre ring cavity.

GTF is a nonlinear phenomenon which allows the formation of MI sidebands whose frequencies position is dependant by the central frequency of a spectral filter. By exploiting a PM fibre Bragg grating, and its double central frequency nature, we are able to generate a double-frequency-comb like spectrum, i.e, a spectra on each polarization with a spectral separation equals to the separation of the filter's components.

A phase-modulated frequency-shifting loop is injected by a single-frequency laser at 1.5 µm. In so-called Talbot conditions, i.e., when the modulation frequency is an integer multiple of the inverse of the cavity round-trip time, the loop generates a frequency comb whose temporal trace consists in a train of pulse doublets whose positions in time depend on the frequency of the injection laser. When the modulation frequency is slightly detuned from the Talbot condition, nonlinear frequency chirps are predicted and observed in the output pulse train. We demonstrate that these nonlinear chirps are not restricted to sinusoidal shapes, and also that the loop can be stabilized by exploiting the intracavity phase modulation.