[16a-316-1~11] 3.14 Optical control devices and optical fibers

[16a-316-4] Effect of optical path length difference between pump and read in distributed measurement of Brillouin dynamic grating spectrum by optical correlation domain technique

〇Takeo Sasai¹, Masato Kishi¹, Kazuo Hotate¹ (1.Univ. of Tokyo)

Keywords:Optical fiber sensor, Brillouin scattering, Optical correlation domain analysis

Recently, optical fiber sensing based on stimulated Brillouin scattering has widely been studied because its characteristics enable us to measure long-range distributed strain and temperature lurking in optical fibers. Particularly, spectrum of Brillouin dynamic grating (BDG), a grating generated in optical fibers by 2 counterpropagating waves, Pump and Probe waves, has the potential to realize discriminative measurement of temperature and strain. For localization of measurement positions, Brillouin optical correlation domain analysis (BOCDA) has been developed. In BOCDA system, sinusoidal FM is applied to Pump and Probe waves. In addition, to get correct spectrum of BDG, Read wave, which is used to read BDG reflection spectrum, also should be synchronously applied the same FM as Pump wave. In this research, we evaluated the effect of the phase mismatch between Pump and Read waves on BDG spectrum.