Di Che, Nokia Bell Labs, USA
Hungchang (James) Chien, Marvell Technology Inc., USA
Sander Jansen, ADVA, Germany
With the advent of coherent detection well over ten years ago, many different modulation formats were investigated to reduce implementation complexity and optimize performance. Multi-carrier modulation formats such as coherent optical OFDM (CO-OFDM) got lots of attention at the time, achieving the first transmission experiment of single-channel 100G and 1T transmission and ultimately leading to the concept of DWDM superchannels. However, the multi-carrier path was not followed by the industry and only single-carrier systems were commercialized at the time. The situation seems to change after a decade. Commercial coherent optics have evolved from 100G to 800G, and a number of industry players have included subcarrier multiplexing (SCM) mode in the latest 800G coherent products.
Will there be a multi-carrier revival? The last workshop at the OFC on multi-carrier modulation formats was back in 2009: “Single-Carrier Versus Multiple-Carrier Modulation Formats for WDM Systems”, so it is about time for an update. This workshop revives the debate from 2009 and address questions like:
- Does single-carrier or multi-carrier transmission have any fundamental and unique advantages over its counterpart?
- What fundamentally changed in the last 10 years to revive multi-carrier modulation in the latest 800G coherent optics?
- Is multi-carrier more difficult than single-carrier to be implemented by real-time DSP? What are the challenges to enable multi-carrier modes for coherent 800G pluggables?
- Multi-carrier is known to have better nonlinear tolerance for QPSK by optimizing the symbol rate per subcarrier. Does this scale to modern systems that employ probabilistically-shaped QAM?
- As the transceiver symbol rate increases, high-frequency degradation issue with higher symbol rate per transceiver and more cascaded ROADMs. Will adaptive multicarrier formats like bit/entropy loading be essential in those bandwidth-constraint scenarios?
- In the Terabit era, will the single-carrier encounter a bandwidth barrier limited by electronics? Will the optical multi-carrier (superchannel) eventually dominate?
The workshop will combine the historical and the state-of-the-art insights on the controversy, aiming to shed light on the future design of ultrahigh speed coherent optics for the Terabit era.
To be determined.