Adaptive transmission technology can effectively inhibit channel fading caused by atmospheric turbulence in wireless optical communications.Under the predefined bit error rate and received signal-to-noise ratio requirement

this paper researched a wireless optical adaptive transmission system due to changing the modulation order through the instantaneous nature of turbulence.Malaga distribution turbulence model is used to describe the distribution of the Gamma-Gamma

Lognormal and K distribution turbulence channel separately

and the related parameters setting methods are given.Analytical expressions of spectrum efficiency

average bit error rate and

outage probability under Malaga channel are derived in the adaptive subcarrier

M

-ary differential phase shift keying (MDPSK) system.Closed form expressions are also derived based MeijerG function.With the comparison between the performance of adaptive modulation and non-adaptive modulation system

the results show that the adaptive system can acquire lower BER performance under the same telecom noise ratio

and also improve the spectrum efficiency without additional transmission power or sacrifice bit error rate.