Programmable Optical Data Transmission Through Multimode Fibres Enabling Confidentiality by Physical Layer Security

Abstract

Complex light transportation phenomena of multimode fibres can be exploited for information-theoretically secure data transmission. The approach called physical layer security is not crackable by quantum computers as it does not rely on mathematical complexity, but on targeted leveraging of properties that are obscured in the physical channel. For its implementation only knowledge of the channel conditions, i.e. the transmission matrix, is required. This allows wiretap code generation, which determine the appropriate mode combination providing secure data transmission. Once the proper combination is launched at the transmitter-side, the message is delivered to the legitimate receiver and, simultaneously, the full decipherment for an eavesdropper is destroyed. This is demonstrated experimentally at presence of an almighty eavesdropper and the fundamental theory is introduced. We harness effects that have long been considered limiting and have restricted the widespread use of multimode fibres opening new perspectives on information-theoretic security in spatial multiplexing communication systems.