  Performance of Free Space Optical (FSO) communication system is affected by
atmospheric turbulences and pointing errors. These effects can easily be
mitigated by adapting natural system parameters such as wavelength. In this
paper, considering effects of pointing error and atmospheric turbulence, two
optimization models are presented on FSO communication system. In Model 1, the
normalized transmitter power is objective function, Bit Error Rate (BER) is
equality subjective. In Model 2 normalized transmitter power is equality
subjective, the BER is objective function. In both of them the normalized
wavelength is variable parameter. These models were previously investigated
using numerical methods; in the sense that they were solved asymptotically.
From this point of view, this paper regenerated these models and solved them by
a completely different analytical method, and derived a new exact solution.
Comparing exact and asymptotic methods shows some interesting results; the
asymptotic method achieves BER=10^(-9), but the presented new exact method
achieves BER=10^(-13), which is a significant difference. It means that even at
the worst case scenario such as pointing error, it is possible to have a very
good performance by only the transmitting wavelength a bit. Proposed models are
practical and obtained results show that this system is cost and power
effective.
