A resonance based optical fiber sensor using a transparent conducting oxide (TCO) coating as the SPR supporting layer is presented here. Traditional resonance based sensors, such as surface plasmon resonance sensors, have been restricted to the utilization of noble metals such as gold and silver as resonance supporting layers. In this work, we present the fabrication of a novel optical fiber resonance based sensor by using a TCO, indium tin oxide (ITO) as the resonance supporting layer with the resonance wavelength in the infra-red region. The refractive index (RI) in the interface ITO/sample can be obtained by monitoring the changes originated in the resonance wavelength peak. The fabricated sensors have been used as refractometers in order to determine the RI of different samples in contact with the ITO layer. These sensors showed high repeatability and a sensitivity in the order of 0.0003 RIU per nm.