Currently, the surface plasmon resonance (SPR) based sensors are mainly focused in visible frequencies, being a barrier for a better integration with the typical fiber optical communication transmission bands. Here, it is presented a theoretical analysis of a SPR based fiber optic sensor with a uniform gold coating on a U-shaped probe. The sensor does not require any fiber etching treatment which eases and improves the control of the overall process. The response of the device to refractive index variations was investigated and a resolution of 10-8 is foreseen for refractive indices around 1.413, becoming the proposed sensor a useful tool for biological and chemical applications.