On-chip regeneration of a frequency comb for 64QAM communications

Summary form only given. An optical frequency comb can generate hundreds of individual comb lines which can be employed in wavelength division multiplexing systems [1], thus reducing the cost, footprint, power consumption and system complexity when compared to using multiple lasers. However to date, comb-based communications have been limited to lower modulation formats more tolerant to phase noise, due to poor carrier to noise ratios resulting from high parametric noise in the comb. We recently proposed a technique [2], to regenerate a C-band optical frequency comb for transmission of 64 QAM signals. This was based on using a narrowband (~10 MHz) amplifier generated through stimulated Brillouin scattering (SBS) in a 4.46-km standard single mode fibre to significantly suppress noise around the carrier thus increasing the carrier to noise power ratio. In this work, we present the regeneration of a C-band 40-GHz comb using SBS on a photonic chip, reducing the length of the SBS medium by more than 4 orders of magnitude and paving the way towards photonic integration and low-cost manufacturing. This work also represents the first-ever implementation of on-chip SBS in high-speed optical communications.