Optical communications through highly scattering channels using the coherence-rank

TL;DR

This paper demonstrates that partially coherent optical fields encoded in the coherence rank can enable scattering-immune optical communication with perfect fidelity in highly scattering channels, surpassing conventional methods.

Contribution

The authors introduce a novel encoding scheme based on the coherence rank of partially coherent fields, providing a new method to achieve robust optical communication in challenging scattering environments.

Findings

Achieved 100% fidelity in scattering channels using coherence-rank encoding.

Partially coherent light can overcome worst-case optical scattering scenarios.

Encoding in coherence rank offers a new approach for robust optical communications.

Abstract

In optical communications, logical bits are encoded in physical degrees-of-freedom (DoFs) of the electromagnetic field. Consequently, optical scattering in a communications channel compromises the information transfer. In the worst-case-scenario, bit-to-bit stochastically varying scattering that couples the DoFs to each other -including even unused DoFs -can decouple the transmitter and receiver when relying on conventional physical encoding schemes, and preclude the utilization of adaptive techniques as a counter-measure. Here we show that partially coherent optical fields help circumvent the worst-case-scenario of rapidly varying, strong optical scattering, even when the channel is rendered informationally opaque for conventional approaches. Using a channel in which the spatial and polarization DoFs are relevant, we encode the logical bits in the unitarily invariant coherence rank (the number of non-zero eigenvalues of the field coherence matrix) and prepare our partially coherent fields with maximal entropies of 0, 1, 1.585, and 2 bits for rank-1, rank-2, rank-3, and rank-4 coherence matrices, respectively. This scheme demonstrates scattering-immune optical communications with 100 % fidelity. These results unveil an unexpected utility for partially coherent light in optical communications through challenging environments.