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We developed a wireless duplex communication system using visible light communication concept. In this work we investigated a downlink data transmission channel. We modelled the optical configuration of the system, calculated optical losses, fabricated the system and measured downlink channel parameters under test of analog and digital signals. The analysis showed that with a heterodyne scheme used for transmitting signals through visible light, the model of additive Gaussian noise is applicable to the channel and there are no phase distortions in the system. The system has shown the capability to operate with modulation types according 802.11 IEEE protocol.

The system of intellectual lighting data transmission via visible light is developed and manufactured. Spectral characteristics of a downlink which uses the red crystal of a RGBW light emitting diode for data transfer were studied. The DALI protocol-based radiation chromaticity control system which allows us to set different lighting scenarios with constant data transmission rate was developed. The radiation chromaticity range covers almost the entire colour gamut in the colour space. The system of high-frequency matching of system component impedances was developed and frequency characteristics of the suggested scheme were studied for development of the system. Optimal parameters of the signal for visual light communication such as carrier frequency, modulation type and band were determined. Observation of the constellation diagram which represents different values of the complex amplitude of the keyed signal in the form of a complex number on a quadrature plane (cosine and sine components of the carrying signal) and of fixation of the amplitude of the error vector magnitude (EVM) was selected as a method of study of the transmission channel quality. The value of EVM in the visible light transmission channel was significantly lower for signals with amplitude modulation than for phase-manipulated signals. When implementing different lighting change scenarios, radiation of other crystals of the light emitting diode crystals not used for transmission did not lead to increase of EVM by more than one percent.

The paper concerns the efficiency of light absorption with different spectral composition by lettuce leaves, and the optimal conditions of light environment and mineral nutrition to increase the productivity and quality of plant products grown under artificial lighting. The greatest positive effect has been achieved on the productivity and quality of the lettuce plants Typhoon variety when been grown on the 1N Knop nutrient solution and illuminated with quasi-continuous spectrum in a limited wavelength range in the yellow area with addition of ∼ 10-20% of the total photosynthetically active radiation (PAR) in the near infrared. The most efficient conditions results in the increase on amount of absorbed photon energy by ∼ 40% per gram of plant leaf surface over 10 days when rapid biomass growth and plant development take place. It is proposed to use the index of light absorption, describing the absorption increment with biomass growth, as an indicator for the intensity of light energy processing into biomass.