On the secrecy capacity of the space-division multiplexed fiber optical communication systems

Recent developments in the field of space-division multiplexing (SDM) for fiber-optic communication systems suggest that the spatial diversity offered by SDM can be used not only to increase system capacity, but also to achieve provable security against physical layer attacks. We examine the information-theoretic security of SDM with a focus on frequency-selective and rapidly-varying frequency-flat channels. We analytically evaluate the outage-free secrecy capacity - the maximal data rate that guarantees perfect security within a class of channel realizations. Using analysis and simulations, we evaluate the impact of key system parameters on the secrecy capacity of SDM systems. Our results show that, with a proper code design that balances the trade-off between data rate and confidentiality, we can take full advantage of SDM to offer a secure information rate that could be orders of magnitude higher than what can be achieved through quantum key distribution (QKD).