Abstract Sunlight Concentrated and transmission for daylighting via optical fibers is a booming technology of direct utilization of solar energy. It uses optical fibers to introduce sunlight deep into building interior. In this work, a sunlight concentrating and transmitting system via plastic optical fibers was developed and tested. This study addressed the cooling problem of the plastic optical fibers under highly irradiation. Polymethylmethacrylate (PMMA) plastic fibers have a strong absorption effect on infrared light, which means that plastic fibers heat up so much when they transmit focused sunlight that they burn. In this study, a comprehensive cooling approach was developed to solve the overheating problem of plastic optical fibers, which consists of an infrared filter, cooling water and a homogenizer. The transmission efficiency of the system was measured to be about 15%. Experiments show that the comprehensive cooling measures developed can ensure that PMMA plastic optical fibers are in a safe temperature range. This shows that it is feasible to use low-cost plastic optical fibers instead of expensive silica fiber to transmit high flux for daylighting.