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Finite difference time domain (FDTD) analysis has been successfully formulated for solving diffusion equation in biological tissues. Time-dependent diffusion equations are approximated by FDTD equations by assigning diffuse photon fluence rates and radiant flux defined in the diffusion equations to Yee meshes. At the boundary between scattering and no scattering material, FDTD equation including only fluence rate has been derived, which make it possible to calculate the fluence rate at the boundary. The formulation is useful to solve diffusion equations by iterative algebraic calculations in scattering media with inhomogeneous optical properties. The conditions to give stabilities for numerical solutions have been become clear in terms of scattering coefficients and mean cosine of scattering angles. Using the formulation, the reflectance of three-layered slabs containing a clear layer have been calculated. As a result, it has been found that absorption loss changes of the highly scattering medium beyond the clear layer are estimated from the time profiles of the reflectance. Index Terms--Diffusion equation, FDTD analysis, optical computer tomography, transmittance and reflectance.

The technology of low-lose splicing for optical fibers is well established, but the long-term reliability assurance of splices has not been studied sufficiently. With the wide introduction of optical cables much effort is being devoted to improve the reliability of arc-fusion splicing and to estimate its lifetime. In this paper, Improvement of the reliability of arc-fusion splices by proof test is studied theoretically as well as experimentally and optimum conditions to assure long-term reliability are established. As a results (1) proof test theory can be applied to the arc-fusion splice and it is possible to estimate the lifetime by knowing the values of parameters n and in; (2) the effect of proof testing is greatly dependent on proof stress as compared to proof time; (3) it is shown that the 20-year failure probability can be suppressed below 10-5 by applying proof stress of 0.15 CPa to the spliced fiber before being reinforced by the heat-shrinkable tube method. [ABSTRACT FROM AUTHOR]

A carrier-injection-type optical switch which operates in the 1.06–1.55 μm wavelength range is designed and fabricated. This switch uses the plasma dispersion effect in GaAs. Switching current is about 90 mA at all in-range wavelengths. Its broad wavelength range is suitable for optical signal processing applications in wavelength division multiplexing transmission systems. [ABSTRACT FROM AUTHOR]