Optical Combs for High-Capacity Transmission and Energy-Optimization of Long-Haul Fiber Cables

That an optical comb-source can be used as a multi-carrier source for data transmission is an almost 20 year old notion, first carried out with fibre-based supercontinuum sources to carry on-off-keying (OOK) modulated data [1]. This technique was expanded to support more than 100 WDM channels [2]. Fibre-based comb sources were optimised to enable coherent transmission over 75 nm [3] with 1520 individual comb lines from one source. Very spectrally-efficient data formats could also be supported [4–5], essentially proving that combs are perfectly compatible with the most advanced communication systems, and even used for investigations of extremely high data rates in the Pbit/s domain [6–7]. Planar optical ring resonators (ORRs) are compact integrated comb sources, which have potential to make practical integrated transmitters including the comb source, and were first suggested and demonstrated in 2009 [8–9]. Soon after came the first demonstrations that these types of combs could also carry OOK data [10], and later that they could indeed also support coherent data formats [11] and to very high data rates [12]. Integrated combs based on ORRs generally suffer from low comb-line power, and new structures were developed to increase the conversion efficiency, such as soliton crystals [13] and dark Kerr combs [14], and demonstrations were made to show that such combs could also support long-haul links [15]. We wanted to investigate the impact of the limited comb-line power on the data-carrying capacity, and found that hundreds of terabit/s could be supported by a supercontinuum-based chip-scale comb source [16], and recently made a rigorous analysis showing that integrated comb sources can support tens of petabit/s [17], and that these sources may prove very energy-efficient. In this presentation, I will also present results on reach implications using integrated combs.