Thermoluminescence flat optical fibers have been proposed as a radiation sensor in the high flux radiation field, e.g. nuclear reactor. It is also used as the medical dosimetry for both diagnostic and radiotherapy applications. Subsequently, a flat optical fiber contains pure silica SiO2 and doped (GeB) optical fibers were selected for this research. The proposed flat optical fibers shows admirable linear radiation response behavior within the medical relevant dose range for all of these energies, high-quality reproductivity, independence of radiation energy and dose rate and exhibits a very low thermal fading. From these results, the proposed flat optical fibers can be used as radiation dosimeter and favorably compares with the widely used of TLD100 dosimeter in medical radiotherapy application.