Fiber optic sensing systems are considered as a potential on-board solution for loads and health monitoring of aeronautic and space applications. The performance of the used sensors needs to be well understood in all operative conditions of the host structure. Test series in cuasi-static conditions performed in the frame of earlier projects showed the influence of temperature, humidity and tensile and compression load cases on the performance of embedded and surface bonded sensors. In the actual ongoing national funded project called ICARO that is presented in this paper, this issue is studied in depth. The influence of the combined effect of fatigue loading and temperature on the sensitivity of Ormocer and polyimide coated FBGSs are determined in tensile and compression tests. Representative testing specimens with embedded optical sensors were prepared following manufacturing processes representative of flight hardware composite systems. The tests showed that both types of sensors performed satisfactory before and after the 106 cycle fatigue tests of ±1200 The Ormocer coated FBGSs showed a constant decrement of their sensitivity of about 2% after the fatigue cycling in the entire temperature range from -100°C to 160°C whilst polyimide coated sensors showed less than 1% changes but with higher standard deviations of the measured values.