Yoshiyuki Suetsugu

Measurement of the nonlinear refractive index in optical fiber by the cross-phase-modulation method with depolarized pump light

Depolarized pump light is used in measurements of the nonlinear refractive index, n2, in optical fiber by the cross-phase-modulation method. High measurement repeatability within ±1% is obtained by this method. The nonlinear refractive index is determined for dispersion-shifted fiber, standard single-mode fiber, pure silica-core single-mode fiber, and dispersion-compensating fiber as 3.35 × 10−20, 2.96 × 10−20, 2.79 × 10−20, and 4.44 × 10−20 m2/W, respectively, at 1.55 μm. This shows that the nonlinear refractive indices of the optical fibers differ greatly according to glass composition.

Estimation of nonlinear refractive index in various silica-based glasses for optical fibers

The dependence of the nonlinear refractive index n2 on glass compositions for optical fibers is clarified. The relation between n2 and germanium- or fluorine-doped SiO2 is calculated on the basis of the measurement of n2 at 1.55 μm with the improved cross-phase-modulation method, taking into account the radial distribution of the optical power in the fibers.

Full characterization of polarization-mode dispersion with random-mode coupling in single-mode optical fibers

Theoretical expression has been derived for polarization-mode dispersion with random-mode coupling in optical fiber by simple means. The square-root dependence of polarization-mode dispersion not only on a fiber length but on a mean-coupling length has been experimentally verified for the first time. This characterization became possible only by the use of highly birefringent polarization-maintaining fiber and introduction of fusion splices with desired coupling lengths.<<ETX>>

Measurement of zero-dispersion wavelength variation in concatenated dispersion-shifted fibers by improved four-wave-mixing technique

Non-destructive and accurate measurement of zero-dispersion wavelength variation in concatenated dispersion shifted fiber link by improved four-wave-mixing technique has been proposed. The improved technique utilizes the characteristics of the four-wave-mixing efficiency that the efficiency always takes the peak value when a pump wavelength meets the zero-dispersion wavelength, independent of the a probe wavelength, and that the period of the power oscillation is different for different probe wavelengths. The validity has been verified by numerical calculations and the experiment using this technique has been successfully demonstrated.