Radio over fiber (RoF) system is the most appropriate combination of fiber optic link and radio waves. Orthogonal frequency division multiplexing (OFDM)-RoF system can increase the capacity of modulation radio frequency (RF) access with high speed data transmission. The purpose of this paper is modeling and simulation an OFDM-RoF system for fiber length up to 100 km by using 16-quadrature amplitude modulation (16-QAM). OptiSystem 13 software is used for simulation. The proposed model of OFDM-RoF system uses two low pass cosine roll off filter (LP-CROF) as filter at the OFDM stage output and two LiNb-Mach Zehnder modulator (LiNb-MZM) as optical modulator. The results of simulation include the spectrum signal visualizers at the OFDM output, RF to optical upconventer (RTO) output as well as 16-QAM received constellation. The results of simulation have shown that increasing of roll off factor value, it will be broadening in filter band transition. The proposed of RoF-OFDM system is able to achieve fiber length up to 100 km uses 16 QAM sequence bit, the received power is 71.617 dBm with electrical and optical amplifications by using 10 Gbps data signal.