Kenichiro TSUJI^*, Hitoshi NODA, and Noriaki ONODERA

Department of Communications Engineering, National Defense Academy, Yokosuka, Kanagawa 239-8686, Japan

(Received June 13, 2012; Accepted September 7, 2012)

We propose a sweep-free measurement technique for distributed Brillouin frequency shift in optical fibers applicable to distributed strain/temperature monitoring systems, using two sets of pump–probe lights generated by two individual laser sources. This technique utilizes the Brillouin gain ratio measured at both the upper and lower side slopes of two different Brillouin spectra induced by two pump lights with different wavelengths. The proposed method offers high-speed measurement due to the combination of the frequency-sweep-free operation and the polarization-insensitive measurement scheme without polarization scramblers. A measurement accuracy of 17.3 με with a spatial resolution of 5 m over 2.6 km sensing length and a capability of kHz sampling rate are experimentally demonstrated.

Key words: Brillouin scattering, BOTDA, distributed strain sensing, sweep-free, real-time measurement

^*E-mail address: kentsuji@nda.ac.jp