Optimum-Transmission Free-Space Optical Communications

TL;DR

This paper explores the use of Prolate Spheroidal Wavefunctions (PSW) as optimal modes for free-space optical communication channels, demonstrating that aperture-truncated Gaussian beams can achieve maximal transmissivity.

Contribution

It shows that the fundamental PSW mode's transmissivity can be approximated by an optimized Gaussian beam, simplifying implementation in free-space optical systems.

Findings

The zero-th order PSW mode maximizes power transfer eigenvalue.

Aperture-truncated Gaussian beams can match PSW mode transmissivity.

Optimized beam waist improves free-space optical communication efficiency.

Abstract

Slepian developed the Prolate Spheroidal Wavefunction (PSW) spatial-mode basis, which forms the normal modes of the Fresnel-propagation kernel of a free-space optical communications channel bookended by hard-circular apertures. The zero-th order PSW mode has the highest power-transfer eigenvalue, exciting which on the transmitter side therefore maximizes the transmissivity for single-spatial-mode communications. We show that the transmissivity performance of this fundamental PSW mode can be obtained by an aperture-truncated Gaussian beam of an optimized beam waist, despite the two mode shapes deviating from one another in the near-field regime.