Nanosecond-latency IM/DD/DSB short-haul to coherent/SSB long-haul converter

We demonstrate an all-analogue converter from optical intensity modulated direct-detection double-side-band signals to field-modulated optical coherent signals, which is based on the Weaver method of generating SSB radio signals. Our format converter is designed to interface short-haul datacentre links to coherent metro/long-haul links. It has almost-zero latency, as it is based on analog electronic processing. As a proof of principle, we demonstrate a system with a 10-km short haul link and a noise-loaded coherent link, transmitting QPSK and 16-QAM. By reconfiguring the link with subsets of its components, we are able to demonstrate that the main impairments are due to the performance of the RF mixers and the directly modulated laser. The performance could be improved by using higher-bandwidth directly modulated lasers and RF mixers.