March 13, 2023

Free-space communications can overcome the logistical difficulties of broadband connections in remote or rural areas. By using long wave infrared (LWIR) quantum cascade lasers (QCLs) as optical sources, high data rates can be transmitted error-free, eliminating the need for physical connections.

By experimenting with live video broadcasting at different levels of video formats, researchers realized free-space live video broadcasting with a room temperature QCL at a wavelength of 8.1 μm. The high definition video format (1280 pixels x 720 pixels) is transmitted at a data rate of 1.485 Gbits/s without any errors.

High definition video broadcasting requires high precision and stable control of the quantum cascade laser in signal transmission. Wavelength Electronics’ QCL driver, QCL2000 LAB, enabled precise current control with minimal electronic noise from the QCL. The driver also provides analog modulation of up to 2-3 MHz for wavelength modulation, allowing the QCL to emit a constant, uninterrupted signal that is subsequently modulated for communication purposes. The transmission was studied for several hours at a time, indicating the long term stability of the QCL2000 LAB current driver. In addition, the stability of the QCL bias current is critical for consistent electrical bandwidth.

The low noise, high stability QCL2000 LAB, can precisely deliver up to 2 A to the laser. This benchtop instrument exhibits noise performance of 1.3 μA RMS up to 100 kHz with an average current noise density of 4 nA/√Hz. Wavelength Electronics’ QCL driver enables high definition video broadcasting with a data rate of 1.485 Gbits/s with low noise and stable laser output. This makes the developed QCL system a reliable tool for real field applications in free-space communication.

The complete case study is available as CS-LD07.

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