Abstract
In this paper, a comparison study of a quantum cascade laser used for signal transmission by free-space optics is presented. The main goal is to define the capabilities of medium-wavelength infrared lasers operated in pulsed or continuous wave (cw) mode through testing and analyzing a laboratory setup of a data link operated at wavelengths of 4.5 µm (pulsed, peak power 3 W) and 4.8 µm (cw, average power ~20 mW). In this spectral range, the link budget is also defined by radiation attenuation in the atmosphere (absorption, scattering, and turbulence interaction). The performed measurements define unique operational aspects of the quantum cascade lasers considering on–off keying modulation. The registered light pulse changes for different parameters of driving current signals determine some limitations in both rate and data range. Finally, we present eye diagrams of the signals obtained using two data links.
Highlights
Free-space optics (FSO), referred to as optical wireless communication (OWC)with Gbit data rate, is an attractive alternative to radio technology
FSO systems use near infrared (NIR, 0.7–1.4 μm) or short wavelength infrared (SWIR, 1.4–3 μm) radiation to transmit information as the “last mile” link [5]
In today’s market, FSO systems are available with a data rate up to 30 Gbps at a distance of ~1.5 km [7]
Summary
Free-space optics (FSO), referred to as optical wireless communication (OWC)with Gbit data rate, is an attractive alternative to radio technology. Compared to other wireless technologies, it provides a high data rate, free-charge spectrum, low cost, simple deployment, low power consumption, no-interference of electromagnetic (EM) signals, and a high security level [2]. FSO systems use near infrared (NIR, 0.7–1.4 μm) or short wavelength infrared (SWIR, 1.4–3 μm) radiation to transmit information as the “last mile” link [5]. These devices enable transmission of tens of Gbps (gigabits per second) over several kilometers, where the installation of other communication technologies (fiber) is too expensive or practically impossible [6]. In today’s market, FSO systems are available with a data rate up to 30 Gbps at a distance of ~1.5 km [7]
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