Pilot-tone-assisted stimulated-Brillouin-scattering-based optical carrier recovery for Kramers-Kronig reception

Optical carrier recovery provides a method to increase the carrier-to-signal power ratio at the receiver side of an optical communications system. Here, we propose to use optical carrier recovery based on stimulated Brillouin scattering to help overcome performance limits of Kramers-Kronig direct detection systems that arise due to the need for a high carrier-to-signal power ratio. By transmitting a low power pilot tone along with the signal, we simplify the stimulated Brillouin scattering based optical carrier recovery subsystem, toward better compatibility with the technology demands of short-reach systems. Experimental results show that after 80 km standard single mode fibre transmission, an 8.8 dB required optical signal-to-noise ratio improvement is achieved by the proposed optical carrier recovery subsystem, when compared with the standard Kramers-Kronig direct detection system. Moreover, we measure a receiver sensitivity enhancement of more than 2.8 dB in an optically pre-amplified receiver. These results indicate the potential of the proposed optical carrier recovery subsystem to improve reach or power requirements for Kramers-Kronig direct detection systems.