Effects of Air Temperature and Relative Humidity on UHF Free Space Optical Communication in Foggy Weather

Abstract

Theoretically, free space optical communication has been proved to be viable and capable of providing high data rates, secured and license-free transmission but it is seriously susceptible to atmospheric conditions/turbulence majorly fog and other primary weather parameters. In this work, the effects of temperature and relative humidity on ultra-high frequency (UHF) optical communication during fog have been investigated using an optical instrumentation system capable of measuring signal strengths and concurrently measured the temperature and relative humidity at two unlicensed frequencies (900 and 1800 MHz). Temperature shows high level negative correlation with signal attenuation between -0.6060 and -0.8599 while relative humidity shows positive correlation coefficient with signal attenuation between 0.5737 and 0.7551 for the frequencies 900 and 1800 MHz respectively. This implies that the relationship between the optical signal attenuation, temperature and relative humidity are higher, stronger and statistically significant. In addition, empirical models for predicting the variations of temperature and relative humidity on UHF optical signal attenuation during fog were developed.