Patent ID: 8287184

Claim:
A fluid physical-quantity measuring method of measuring a flow rate of a fluid that flows through a pipe line by using a BOCDA-type optical fiber sensor, said measuring method comprising the steps of: preparing an optical fiber whose at least part is arranged in said pipe line along a flow direction of the fluid; inputting pumping light from one end of said optical fiber, while inputting probe light from the other end of said optical fiber; measuring Brillouin gain spectrum induced at a desired position of said optical fiber in a longitudinal direction thereof, by modulating frequencies of the pumping light and probe light inputted oppositely from both ends of said optical fiber; and determining the flow rate of the fluid that flows through said pipe line, on the basis of a measurement result of temperature distribution along the longitudinal direction of a portion of said optical fiber which is located within said pipe line, and a temporal change of the temperature distribution.