Coexistence of 1 Tbps classical optical communication and quantum key distribution over a 100.96 km few-mode fiber.

The integration of quantum key distribution (QKD) and classical optical communication has attracted widespread attention. In this Letter, we experimentally demonstrate a real-time co-propagation of 1 Tbps for 10 classical channels with one discrete-variable QKD channel in the weakly coupled few-mode fiber (FMF). Based on the selection of optimal device parameters and wavelength assignment of classical channels, as well as the optimization of equipment performance, a secure key rate of as high as 2.7 kbps of coexistence transmission of QKD and classical optical communication can be achieved using a 100.96 km weakly coupled FMF. Therefore, this study is a step toward realizing long-distance quantum-classical coexistence transmission.