ABSTRACTIn this work, we describe a novel and cost effective approach based on optical fiber microcavities, for sensing high temperature values (up to 1150°C). The proposed sensor is produced by splicing standard single mode optical fibers with fibers destroyed by the catastrophic fuse effect, resulting in a microcavity structure in the fiber core region. These microcavities have a thermal sensitivity of 10.43 ± 0.15 pm °C−1, for temperatures up to 1150°C, which compares well with the sensitivity of Fabry–Perot interferometric sensing cavities but with the advantage of substantially reduced manufacturing costs. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:972–974, 2015