Analysis of temporal broadening of optical pulses by atmospheric dispersion in laser communication system

In this paper, pulse broadening caused by atmospheric dispersion is analyzed, which is the key factor in high-speed and long-distance free space laser communication systems according to our simulation. The measured datum of atmospheric parameters, including atmospheric pressure and atmospheric temperature of the desert in Xinjiang, China, is used in the analysis of pulses broadening. The pulse broadening caused by atmospheric dispersion is very significant when pulsewidth is on the order of 5 ps, and pulse broadening is negligible if the pulsewidth is larger than 20 ps. With the increment of optical wavelength, atmospheric dispersion-induced pulse broadening is mitigated. The received pulsewidth is dominated mainly by dispersion-induced pulse broadening at small duty ratio of original signal, and original pulsewidth at large duty ratio of original signal respectively. By selecting proper duty ratio of optical pulse, the received pulsewidth can be minimized and the system bit rate can be maximized.