Brillouin optical time-domain analysis (BOTDA) [1,2] and Brillouin optical time-domain reflectometry (BOTDR) selleck chemicals Veliparib [3,4] are distributed measurement techniques utilizing this property by injecting a pulsed pump light and observing the scattered light. The amount of strain/temperature change is estimated by measuring the spectral shift, while its position is determined by the round-trip time of the light. Since BOTDR uses only one end of a fiber, it is suitable for long distance measurement, whereas BOTDA uses pump and probe lights that are injected from both ends of a fiber.To improve the spatial resolution of both techniques, it is necessary to narrow the pulse; however, the linewidth of the observed spectrum then becomes wider and makes measurement of the spectral shift difficult.

For this reason, the spatial resolution has been limited to about one meter in both techniques [5,6].For BOTDA, Bao et al. [7] found experimentally a phenomenon in which the spectral linewidth becomes shorter when a very short pulse of about 1 ns is used. This phenomenon arises only when there is light leakage. Inspired by Inhibitors,Modulators,Libraries this discovery, various resolution improvement methods have been proposed [8�C14]. The pump light of BOTDA plays two roles: phonon excitation and scattering by the phonons. The width of the pump light must be longer than the phonon lifetime (about 9 ns) for phonon excitation, whereas it must be much shorter than 10 ns, which corresponds to a one-meter resolution, for high spatial resolution. To satisfy these incompatible requirements, an idea to construct a pump light using a long and a short element was born.

The long element, which is a long pulse or a CWwave, takes the role of phonon excitation, and the short element takes the role of being scattered by the phonons. A part of the spectrum is by the combination Inhibitors,Modulators,Libraries of these elements. By emphasizing this desired part, high-resolution measurement could be attained.For the construction of pump light from two elements, the authors of [8�C11] used amplitude modulation and [12,14] used phase modulation. In any construction Inhibitors,Modulators,Libraries method, the measured spectrum includes both desired and undesired parts. Parameters must be optimized to emphasize only the desired part. Inhibitors,Modulators,Libraries Instead of that, the Batimastat authors of [12�C14] proposed methods to suppress or cancel the undesired part of the spectrum by combining two different measurements.

By these methods, high-resolution measurement Ivacaftor cystic fibrosis of centimeter-order for BOTDA has been attained.On the other hand, the pump light of BOTDR plays a single role, since the BOTDR utilizes spontaneous scattering, so that it is difficult to attain high resolution by the same idea as for BOTDA. For resolution improvement of BOTDR, Koyamada et al. [15] proposed a double pulse method that yields an oscillatory Brillouin spectrum and verified 20-cm spatial resolution by experiment.In this paper, we propose a novel method, referred to as synthetic BOTDR (S-BOTDR), to improve the spatial resolution of BOTDR.