EVOLUTION OF RADIO OVER FREE SPACE OPTICAL COMMUNICATION UTILIZING SUBCARRIER MULTIPLEXING / AMPLITUDE SHIFT KEYING
The high demand for increased bandwidth, data rate and quality in optical communication systems in modern applications. Radio over free space optics (RoFSO) is deemed a new design methodology over wireless systems and networks. This technique has to ensure data rates like ones presented by means optical fiber communication techniques in keeping with a portion of its arrangement cost. Such systems are implemented by combined radio signal (RF) with optical signal, which containing various wireless administrations and Free Space Optics (FSO) link. In this paper, the simulation and evaluation system of Subcarrier Multiplexing/Amplitude Shift Keying (SCM/ASK) transmitter for Free Space Optical Communication is proposed. 1Gb/s data Rate given to the system. Whilst 10 GHz radio frequency signal setting in electrical amplitude modulator. Thereafter, radio signal is added with 100 subcarrier channels of 10 MHz spacing channel at operated first channel frequency of 60 MHz. These subcarrier channels with 900 combined with 10 GHz sin wave signal ( radio frequency ) at hybrid coupler, the combination of each subcarriers and radio signal are modulated by LiNb Mach-Zehnder optical modulator with 1550 nm wavelength continues wave laser signal at 10 dBm input power. The optical modulated signal (after optical modulator) is transmitted over a various free space optical link from 300m to 1km under the Atmospheric turbulence effect (the structure feature of the refractive index). The system is evaluated utilizing Opti system software with Q-factor and BER terminology. It is shown that the maximum optical distance for weak turbulence ( C n 2 =5× 10 -15 m -2 3 ) at BER equal to 10-9 is 950m, while the maximum optical distance for strong turbulence C n 2 =5× 10 -13 m -2 3 ) is 850m.