Mid-infrared free space communications with quantum cascade lasers

Abstract

This study demonstrates the performance of a free-space optical communication system based on quantum cascade lasers. The experimental setup includes a quantum cascade lasers with a wavelength of 9 micrometers, a modulator, and a photodetector, operating at a bit rate of 7 Gbit/s and an initial power of 50 mW. The key components and their configuration ensure consistent and reliable data transmission over a distance of 1000 meters. In the experiment, a random binary signal is modulated into laser pulses by the quantum cascade lasers and transmitted through free space. Atmospheric particles and gases' effects on signal strength are considered, path loss is calculated and applied to the transmitted signal. Upon receiving the signal, the data is recovered and analyzed to compare it with the original data, evaluating the system's performance. Results indicate that at a transmission rate of 7 Gbit/s, the system's signal to-noise ratio (SNR) can be optimized to its maximum value, ensuring clear and reliable data transmission. Additionally, eye diagrams and bit error rate (BER) analysis demonstrate the system's high-quality transmission at high bit rates. This study shows that quantum cascade lasers have significant advantages in free-space optical communication, especially for high-bandwidth, low latency, and high-security data transmission needs. However, the production cost and precision adjustment requirements of quantum cascade lasers systems remain challenges for widespread application. Future research should focus on reducing quantum cascade lasers production costs, optimizing system performance, improving environmental adaptability, and exploring multi-field applications to fully realize the potential of quantum cascade lasers in free-space optical communication.