Mitsuhiro Tateda

Development of a distributed sensing technique using Brillouin scattering

This paper reviews the developments of a distributed strain and temperature sensing technique that uses Brillouin scattering in single-mode optical fibers. This technique is based on strain- and temperature-induced changes in the Brillouin frequency shift. Several approaches for measuring the weak Brillouin line are compared. >

Tensile strain dependence of Brillouin frequency shift in silica optical fibers

Brillouin frequency shift in a single-mode optical fiber has been measured as a function of tensile strain. The strain coefficient of normalized Brillouin frequency shift C identical to (dv/sub B//d epsilon )/v/sub B/ is found to be 4.4 for silica fibers. This result shows the potential of Brillouin spectroscopy to evaluate tensile strain in the fiber with the strain resolution of about 2*10/sup -4/. The origin of the large strain coefficient is discussed.<<ETX>>

BOTDA-nondestructive measurement of single-mode optical fiber attenuation characteristics using Brillouin interaction: theory

A theoretical investigation of Brillouin optical-fiber time-domain analysis (BOTDA) is described. BOTDA uses Brillouin interaction in optical fibers to analyze the attenuation characteristics of the optical fibers nondestructively. The dynamic range performance of BOTDA is approximately 10-dB greater than that of conventional optical time-domain reflectometry. >

Distributed-temperature sensing using stimulated Brillouin scattering in optical silica fibers

Temperature distribution in silica single-mode optical fibers, from -30 to +60 degrees C, is successfully measured by using Brillouin optical-fiber time-domain analysis. A temperature measurement accuracy of 3 degrees C with a spatial resolution of 100 m is attained over a fiber length of 1.2 km.

A technique to measure distributed strain in optical fibers

The technique is based on Brillouin optical-fiber time-domain analysis (BOTDA), which uses Brillouin interaction between counterpropagating pump and probe light waves. Experimental results for fibers wound on drums at various tensions are presented. A strain measurement accuracy of better than 2*10/sup -5/ and a spatial resolution of 100 m are achieved.<<ETX>>

Interferometric method for chromatic dispersion measurement in a single-mode optical fiber

Chromatic dispersion of a single-mode optical fiber only 1 m long is measured by a newly proposed interferometric method. Interference fringes are produced by two laser beams, one transmitting through the fiber and the other through air. Path length shifts in an interferometer for attaining the visibility maximum are measured by varying optical source wavelengths between 818 and 904 nm. Group delay time differences around 1 ps are measured. The measured results are in good agreement with those measured by the conventional pulse method for the identical 1.3 km long fiber.

Thermal effects on the Brillouin frequency shift in jacketed optical silica fibers

Brillouin frequency shift in two kinds of jacketed optical single-mode silica fiber, with an ultraviolet curable resin coat and a nylon coat, has been measured at temperatures ranging from -30 to +60 degrees C. It has been found that there are two reasons for the Brillouin frequency shift change in jacketed optical fibers against temperature change. One is the Brillouin frequency shift change for bare fibers. The other is the thermal stress due to the differences in thermal expansion coefficients in bare fiber and its coating material.

Optical-fiber-attenuation investigation using stimulated Brillouin scattering between a pulse and a continuous wave

A new technique for measuring optical-fiber-attenuation characteristics is described. The technique uses stimulated Brillouin scattering in the fiber between a counterpropagating pulsed pump wave and a cw Stokes probe wave. Fiber attenuation is estimated nondestructively from amplification of the probe wave through stimulated Brillouin scattering. Experiments with a 5.2-km-long single-mode fiber reveal that the output signal is approximately 100 times that of the Rayleigh backscattered signal observed in conventional optical time-domain reflectometry. The signal fluctuation due to polarization-dependent Brillouin gain is successfully removed by polarization averaging.

Diode-pumped, self-stimulating, passively Q-switched Nd3+:PbWO4 Raman laser

Abstract A laser diode transversely pumped compact, passively Q-switched, self-stimulating Nd 3+ :PbWO 4 /Cr 4+ :YAG Raman laser is proposed. With 4.5 mJ diode pumping, fundamental and Raman output energies of 2 and 2.5 μJ have been obtained simultaneously at 1.058 and 1.17 μm, respectively. The frequency conversion efficiency is estimated to be 56%. The Raman pulse width of 8 ns is 40% of the fundamental laser pulse width of 20 ns.

Advances in optical time domain reflectometry

Advances in optical time-domain reflectometry (OTDR), such as enlargement of dynamic range, enhancement in resolution, reduction of noise intrinsic to single-mode fibers, and increase in user friendliness of the equipment, are reviewed. The gated detection technique and recent progress in OTDR are presented. Future optical network diagnostics are discussed. >