Patent ID: 7227123

Claim:
A physical quantity measuring method using a Brillouin optical fiber sensor comprising: a step S 1000 of setting an optical fiber 100 on a predetermined structure as a sensing structure; a step S 2000 of selecting a pair of first and second pulse lights having different pulse widths; a step S 3000 of sequentially transmitting the first and second pulse lights through the optical fiber 100 to obtain Brillouin gain spectra; a step S 4000 of comparing the Brillouin gain spectra with each other to obtain a normal spectrum; a step S 5000 of determining a Brillouin frequency having a peak value from the normal spectrum; and a step S 6000 of multiplying the Brillouin frequency by a conversion factor of a physical quantity to be measured resulting in a measurement of the physical quantity wherein the measurement is outputted as a signal; wherein the normal spectrum is obtained using the following equation, NBGS ⁡ ( x , v ) = I ( 2 ) ⁡ ( x , v ) I ( 1 ) ⁡ ( x , v ) = exp ⁡ [ ∫ x + Δ ⁢ ⁢ z 1 x + Δ ⁢ ⁢ z 2 ⁢ g ⁡ ( z ′ , v ) ⁢ Δ ⁢ ⁢ I pu ⁡ ( z ′ , v ) ⁢ ⁢ ⅆ z ′ ] wherein NBGS(x,v) represents the normalized Brillouin gain spectrum, which means back scattering lights accumulated in the portion corresponding to Δz 2 −Δz 1 , I (1) (x,v) denotes the first Brillouin gain spectrum, I (2) (x,v) represents the second Brillouin gain spectrum, x means the position where each back scattering light starts, g(z′,v) represents a Brillouin gain factor, and ΔI pu (z′,v) denotes the intensity of each pulse light.