Optical fiber day lighting systems help the efficiency of using solar energy in the lighting system in domestic, industrial and agricultural sectors. A lot of work has been done on these systems, but the lack of a reliable simulation method to reduce the tolerance, time and cost is evident. In this regard, in this paper, a novel method based on two powerful Optifiber and Zemax software has been proposed for simulating and optimizing an optical fiber daylighting system to increase the efficiency of output power from the fiber. A comparison has been made between popular types of polymer fibers with OptiFiber software, which shows the maximum propagation of modes in PMMA polystyrene fiber. Extracted detailed characteristics from Optifiber related to the selected fiber with 1mm diameter have been implemented in Zemax software and a daylighting system has been simulated. The coupling of light into the optical fiber has been optimized with the Global Optimization Method based on the genetic algorithm. By selecting a 100 watts resource as the sun according to the AM 1.5 standard, the simulation indicates a transfer of 22 watts of power. After optimization, this power increases to 30 watts, which shows the role of optimization in increasing the efficiency to 36%. Practical results by testing on a system with intensity measurement confirm the simulation results. As a result, by choosing the right fiber and accurately determining the characteristics, and optimizing the coupling into the fiber, it is possible to help increasing the efficiency of optical fiber daylighting systems.