This article presents the effects of haze attenuation on Radio over Free Space Optic (RoFSO) transmission system in KLIA Sepang, one of the towns in Malaysia. The haze condition which affects the FSO link transmissions was considered on October 2015 and on October 2017 at KLIA Sepang referring to the reading record of Air Pollution Index (API). In this paper, OptiSystem simulation software is used as a preliminary study before configuring the real RoFSO setup. We model the RoFSO by converting the radio frequency (RF) signal into light where the light source intensity is modulated with the RF signal. RF signal travels through free space while light propagates through fiber optic channel. Single-FSO and four- FSO channels are compared and analyzed in terms of bit-error-rate (BER), received optical power and eye diagram pattern. The results show that the performance of RoFSO with four-FSO channel system in comparison with single-channel has better receiver sensitivity and clear eye diagram. For future work, deploying multiple RoFSO system can fulfil the increasing demand for optimizing the communication bandwidth.