To provide a stable optical fiber Bragg grating(FBG) temperature sensor with high temperature measurement precision by storing an optical fiber sensor provided with an optical fiber Bragg grating(FBG) in a part of an optical fiber and partially bent into a U-shape in a part other than the FBG formation part inside a housing.
A FBG temperature sensor is provided with an optical fiber sensor 1A in which a FBG 12 is formed in a part of an optical fiber 11. In addition, a thermosensitive member 2 transmitting heat from a temperature measuring part in a temperature measuring pipe to the FBG 12 forming part in the optical fiber sensor 1A is provided. The optical fiber sensor 1A and the thermosensitive member 2 are fixed by a highly heat-resistant adhesive, and in both ends of the optical fiber sensor 1A, optical fiber connectors 3a, 3b are mounted. The optical fiber sensor 1A is bent at the position other than the FBG 12 forming part, so that the optical fiber sensor 1A can be housed in the temperature measuring tube without applying distortion to the FBG 12 part.