The composite dielectric waveguides with multi-boundaries in radial directions have axially unsymmetrical structures. To have the large difference in propagation constant for the two orthogonal HE₁₁ modes, the waveguides have attracted our attention as a new type of single-polarization optical fibers. In this paper, the modal characteristics of the composite dielectric waveguides are investigated by a numerical analysis based on the point-matching method. The dispersion characteristics for millimetric dielectric waveguides with large difference in dielectric constant as well as single polarization optical fibers with small difference in refractive index are shown. Also, the patterns of electric field distributions for propagating modes are illustrated. The propagation constants are obtained with three significant figures for both the dominant and higher order modes. Microwave model experiments using a composite dielectric waveguide made of Rexolite and Teflon were carried out to confirm the theory.

If there is high uncertainty in the reliability of a system, it is required to know for which components to collect further failure data for making the uncertainty lower. This paper provides some solutions for such a requirement. First, the variance importance of a component is defined as a measure of component's contribution to the variance of the distribution of system unreliability. For reducing the system-variance efficiently, it would be suitable to collect failure data of comopnents having greater values of variance importance. Next, in the situation that we will perform life tests of components for making the variance of the distribution of system failure-rate smaller than its prior value, some problems for determinig both the number of samples to be tested and the test time for each component are formulated and solved.

This paper deals with two optimal preventive maintenance policies, i.e., Policy I and Policy II proposed by R. Barlow and L. Hunter, and in particular emphasizes on the characteristics of the optimal maintenance theories due to numerical analysis. Through this paper, the Weibull model is adopted as a failure modes and its shape parameter β plays an important role. According to the results newly obtained, we discuss the characteristics of the two types of policies and their advantages and disadvantages. Next, the new results are applied to the field data of failure and maintenance in order to investigate the actural maintenance techniques.

In this short note, an upper limit of modulation enhancement of electronic phase shifter employing a multilayer dielectric-waveguide structure is provided by the application of general theory of dielectric waveguides.