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

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 Mbit/s is also demonstrated. (C) 2022 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement

Automated summary

This article demonstrates the applicability of quantum cascade laser frequency combs in free-space optical communication. The analog signal is transferred using the spontaneously-generated intermodal beat note of the frequency comb as the carrier for frequency modulation. It also showcases the potential for parallel transmission of independent digital signals through amplitude modulation.