A model for a coherent orthogonal frequency division multiplexing (OFDM) system as well as Fast-OFDM system in both terrestrial and underwater wireless optical communication, has been proposed, that can be tuned with the virtual local oscillator, under the Gamma-Gamma atmospheric turbulence channel. Not only just considering the intensity scintillation but also considering the phase noise caused by atmospheric turbulence effect on the performance of the system. Analysis will be done under the premise of the different number of subcarriers, the influence of each parameter of atmospheric channel on the bit error, and the communication interrupt performance of the OFDM-FSO and F-OFDM-FSO systems, respectively. The result will confirm that the Fast-OFDM in both terrestrial and underwater wireless optical system may obtain higher sensitivity and hence overcome the bad atmosphere influence to obtain good performance of the system, even after the subcarrier spacing is reduced to half of that in the conventional OFDM systems. © 2006-2016 Asian Research Publishing Network (ARPN). All rights reserved.