Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)A fiber optic sensor for simultaneous measurement of refractive index and temperature is presented. The sensing probe is realized by introducing a multimode interference device inside a high birefringence fiber loop mirror resulting in a configuration capable of refractive index and temperature discrimination. The multimode interference peak is sensitive to the surrounding refractive index (90 nm/RIU) and slightly responsive to the temperature (0.01 nm/ degrees C). On the other hand, the birefringent fiber loop mirror is highly sensitive to temperature (2.36 nm/ degrees C) and it has almost no response to refractive index. Using a power ratiometric peak detection scheme, a temperature independent refractive index measurement can be achieved with a resolution of +/- 2.25 x 10(-5) RIU. (c) 2012 Elsevier B.V. All rights reserved.177717723Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)project AQUA-MONITOR [FCOMP-01-0124-FEDER-013911, PTDC/AAC-AMB/112424/2009]FCT [SFRH/BD/63758/2009]Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)project AQUA-MONITOR [FCOMP-01-0124-FEDER-013911, PTDC/AAC-AMB/112424/2009]FCT [SFRH/BD/63758/2009]