Wavelength-Division Multiplexing Optical Transmission for EMI-Free Indoor Fine Particulate Matter Monitoring

Air pollution has become a global issue from the perspective of public health and the social economy. Of the various air pollutants, fine particulate matter (PM2.5), which is less than 2.5 micrometers in diameter, can cause serious health problems such as asthma, lung cancer, respiratory diseases, cardiovascular disease, birth defects, and premature death. The ability to have accurate dust information in real-life is very important for patients with respiratory illnesses. Visible-light communication, which performs the functions of illumination and data transmission in indoor environments, could be utilized for the long-term transmission of important environment information, even in places where RF transmissions are restricted, such as medical centers, emergency rooms, or nursing homes. In this paper, a prototype of a wavelength division multiplexing optical transmission system is proposed for electromagnetic interference-free indoor dust monitoring. Important indoor environment information, such as dust concentration, temperature, and relative humidity, are transferred by red green blue (RGB) light sources. A single RGB-type white light-emitting diode and a single color sensor are adopted to enable a low-complexity implementation. An average voltage-tracking technique is utilized for robust light detection to eliminate ambient light and low-frequency noise. The incoming RGB lights are separated by a color sensor, and are simultaneously processed by a receiver microcontroller. Medical experts and patients can then monitor indoor air quality in real-time, and they can improve the environmental awareness of individuals.