Differential Phase-Shift QKD in a 2:16-Split Lit PON with 19 Carrier-Grade Channels

TL;DR

This paper demonstrates the practical integration of differential phase-shift quantum key distribution in a cost-effective passive optical network supporting up to 19 classical channels, achieving secure key rates over 13.5 km with minimal error penalty.

Contribution

It presents a novel deployment scheme for QKD in existing optical networks, using simple user equipment and analyzing coexistence with multiple classical channels across various spectral bands.

Findings

Quantum channel coexists with 19 classical channels.

Secure key rate of 5.1×10^-7 bits per pulse at 13.5 km.

Low error penalty of 0.52% due to high classical-quantum power difference.

Abstract

We investigate the practical network integration of differential phase shift quantum key distribution following a cost-optimized deployment scheme where complexity is off-loaded to a centralized location. User terminal equipment for quantum state preparation at 1 GHz symbol rate is kept technologically lean through use of a directly-modulated laser as optical encoder. Integration in a passive optical network infrastructure is experimentally studied for legacy and modern optical access standards. We analyze the implications that result from Raman scattering arising from different spectral allocations of the classical channels in the O-, S-, C- and L-band, and prove that the quantum channel can co-exist with up to 19 classical channels of a fully-loaded modern access standard. Secure-key generation at a rate of 5.1 times 10e-7 bits per pulse at a quantum bit error ratio of 3.28 percent is obtained over a 13.5 km reach, 2 to 16 split passive network configuration. The high power difference of 93.8 dB between launched classical and quantum signals in the lit access network leads to a low penalty of 0.52 percent in terms of error ratio.