Analog FM free-space optical communication based on a mid-infrared quantum cascade laser frequency comb

TL;DR

This paper demonstrates analog free-space optical communication using a mid-infrared quantum cascade laser frequency comb, achieving high SNR and bandwidth, with potential for parallel digital transmission.

Contribution

It introduces a novel application of quantum cascade laser frequency combs for free-space optical communication in the mid-infrared range.

Findings

Achieved up to 65 dB SNR in optical communication.

Demonstrated 300 kHz modulation bandwidth.

Tolerated optical attenuation exceeding 35 dB.

Abstract

Quantum cascade laser frequency combs are nowadays well-appreciated sources for infrared spectroscopy. Here their applicability for free-space optical communication is demonstrated. The spontaneously-generated intermodal beat note of the frequency comb is used as carrier for transferring the analog signal via frequency modulation. Exploiting the atmospheric transparency window at 4 $\mu$m, an optical communication with a signal-to-noise ratio up to 65 dB is realized, with a modulation bandwidth of 300 kHz. The system tolerates a maximum optical attenuation exceeding 35 dB. The possibility of parallel transmission of an independent digital signal via amplitude modulation at 5 MS/s is also demonstrated.