High-sensitivity thermometer based on singlemode-multimode FBG-singlemode fiber

A fiber Bragg grating (FBG) sensing configuration for temperature measurement based on singlemode-multimode FBG-singlemode fiber was proposed and experimentally demonstrated. The configuration was formed by fabricating an FBG in a multimode fiber, which was sandwiched between two singlemode fibers. Both theoretical and experimental analyses were performed. An average sensitivity of 266.25 pm/°C and a resolvable index change of 3.75 × 10−2 °C were obtained in the temperature range from −40 °C to +40 °C. The proposed thermometer could find useful applications in biology, medicine, and material science because of its superior properties such as high sensitivity, compact size, easy fabrication, linear response, ease of interconnection with other in-fiber optical components, and low cost.