FSO communications constantly flourish, because of the numerous efficient and economic benefits, highlighted by many researchers and exploited by many manufacturers; however, FSO channels are not free of various performance limitations. This work concerns FSO links’ availability estimation by taking into account both, the propagation into a dispersive media and the time jitter influence. Particularly, the truncated normal distribution has been used in order to investigate the time jitter effect on chirped longitudinal Gaussian pulses. The links’ performance is presented in terms of either probability of fade or outage probability, in closed form mathematical expressions. The work is concluded with the corresponding numerical results and inferences, using typical and realistic parameters of operating FSO systems.