Modal division multiplexing of quantum and classical signals in few-mode fibers

TL;DR

This paper experimentally demonstrates the simultaneous transmission of quantum and classical signals in few-mode fibers, highlighting the potential for secure, high-capacity communication systems using mode-division multiplexing.

Contribution

It introduces the first experimental study of quantum and classical signal multiplexing in few-mode fibers at telecom wavelengths, addressing mode coupling and cross-talk issues.

Findings

Quantum and classical signals can be multiplexed in few-mode fibers.

Random mode coupling causes cross-talk among channels.

Feasibility of secure quantum-classical communication in spatial multiplexing.

Abstract

Mode-division multiplexing using multimode optical fibers has been intensively studied in recent years, in order to alleviate the transmission capacity crunch. Moreover, the need for secure information transmission based on quantum encryption protocols leads to investigating the possibility of multiplexing both quantum and classical signals in the same fiber. In this work, we experimentally study the modal multiplexing of both quantum and classical signals at telecom wavelengths, by using a few-mode fiber of 8 km and modal multiplexers/demultiplexers. We observe the existence of random-mode coupling at the quantum level, leading to cross-talk among both degenerate and non-degenerate channels. Our results demonstrate the feasibility of using few-mode fibers for simultaneously transmitting classical and quantum information, leading to an efficient implementation of physical information encryption protocols in spatial-division multiplexed systems.