Abstract
This article is a short study of the application of high-power quantum cascade lasers and photodetectors in medium-infrared optical wireless communications (OWC). The link range is mainly determined by the transmitted beam parameters and the performance of the light sensor. The light power and the photodetector noise directly determine the signal-to-noise power ratio. This ratio could be maximized in the case of minimizing the radiation losses caused by atmospheric attenuation. It can be obtained by applying both radiation sources and sensors operated in the medium infrared range decreasing the effects of absorption, scattering or scintillation, beam spreading, and beam wandering. The development of a new class of laser sources based on quantum cascade structures becomes a prospective alternative. Regarding the literature, there are descriptions of some preliminary research applying these lasers in data transmission. To provide a high data transfer rate, continuous wave (cw) lasers are commonly used. However, they are characterized by low power (a few tens of mWatts) limiting their link range. Also, only a few high-power pulsed lasers (a few hundreds of mWatts) were tested. Due to their limited pulse duty cycle, the obtained modulation bandwidth was lower than 1 MHz. The main goal of this study is to experimentally determine the capabilities of the currently developed state-of-the-art high-power pulsed quantum cascade (QC) lasers and photodetectors in OWC systems. Finally, the data link range using optical pulses of a QC laser of ~2 W, operated at the wavelength of ~4.5 µm, is discussed.
Highlights
The mid-infrared wavelength range (MWIR) is very promising for many applications
This article is a short study of the application of high-power quantum cascade lasers and photodetectors in medium-infrared optical wireless communications (OWC)
The conducted literature reviews show that there is no information about the application of a high-power pulsed quantum cascade (QC) laser in an OWC system [4]
Summary
The mid-infrared wavelength range (MWIR) is very promising for many applications. The main ones are chemical sensing and spectroscopy developed for the pharmaceutical sector, biomedical analysis, atmospheric chemistry, detection of dangerous substances and materials, etc. The conducted literature reviews show that there is no information about the application of a high-power pulsed QC laser in an OWC system [4] It results mainly from a low duty cycle (dc) of its generated light pulses limiting the format of signal coding. The described technology enables designing data links with high-power lasing structures operating at the wavelength of 4.5 μm with a peak pulse power of 3 W. Random wave front interference causes peaks and dips in the high-dynamic receiver output signal This effect can be minimized using, for example, aperture averaging, diversity techniques, adaptive optics, or some modulation techniques [35]. Where Ndet is the photodetector noise signal, G is the signal gain of the photodetector front-end, and Nf −e is the front-end noise contribution
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