We had earlier demonstrated the distributed discrimination of strain and temperature by localizing and scanning both the stimulated Brillouin scattering and the Brillouin dynamic grating along a polarization-maintaining fiber. The localization and scanning were performed by a correlation domain technique, whose measurement range was restricted by the distance between consecutive correlation peaks. To overcome this restriction, in this letter, we apply a temporal gating scheme to the system by enlarging the measurement range from ∼25 to ∼500 m. We report the results confirming the effectiveness of this scheme in a system operated by a single laser source, and demonstrate the strain-temperature discrimination when strain or temperature is applied to segments on the 500-m-long fiber under test.Index Terms-Brillouin fiber-optic sensor, distributed sensing, strain-temperature discrimination.

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We numerically analyzed reflection spectrum of Brillouin dynamic grating localized by intensity-modulated correlation-domain technique. Furthermore, based on the results, we proposed a novel modulation technique achieving better spatial resolution for distributed fiber sensing along a polarization-maintaining fiber.

We derive formulae based on Fourier transformation to calculate the reflection spectrum of a Brillouin dynamic grating (BDG), which is localized along an optical fiber by an optical correlation domain technique. First, we calculate the typical reflection spectra of the BDG localized by the technique and confirm the validity of the formulae by showing coincidence with previous theoretical or experimental works. Next, we evaluate theoretically the spatial resolution in the BDG distributed measurement by the technique, through simulations considering different strained fiber lengths. It is confirmed theoretically, for the first time, that the resolution in the BDG measurement is worse than that for the Brillouin gain spectrum.