The main objective of this paper is to study the dielectric behavior of a quaternary composite, made from a mixture of barium titanate (BT), manganese dioxide (MnO2) and calcium oxide (CaO) in the same epoxy resin matrix (RE) maintained at 70% by volume fraction, while those of the other constituents are variable and completing each other in a way to achieve the remaining proportion, i.e. 30%. Random mixtures are made at room temperature and under atmospheric pressure. A dielectric characterization of this mixture type was performed by time-domain spectroscopy (TDS) over a frequency wide band (DC–2 GHz). This has been carried out to illustrate the effect of two oxides (MnO2 and CaO) simultaneously at low frequency (500 MHz), in the presence of (BT), on the composite dielectric behavior. This has led consequently to make a comparison between the present acquired results and those of the ternary composite, where (MnO2) and (CaO) act separately. The results obtained so far in this study allowed us to check the validity of the modified Lichtenecker law (MLL)-based predictive model in the quaternary composite case. The interest of this study lies on applications of these materials in microelectronics circuits and absorber materials in telecommunication domain.

In this paper, we have proposed three types of taper structures called L.C.C (L : linear, C : concave and C : convex) that form at the end of the optical fibers in order to use them for detection in order to improve the formation of evanescence waves on the surface of the fiber We studied on these three types of structure four materials such as: silicon (Si), glass (SiO2), sapphire (Al2O3) and zircon (ZrSiO4) with refractive index 1.45, 1.52, 1.77 and 1.92, respectively. First, the three structures are designed in a taper shape with a length "L" fixed at 50m and a diameter "D" equal to 10m. Then, they shrink to 1m in diameter 'from the end of their structures. We used an optical DC source with a power amplitude of 1V/m. We also simulated these "L.C.C" structures with the OptiFDTD simulation software, which is based on the finite difference time domain (FDTD) method. Our numerical results are obtained to extract the electric field (TE) distribution of the evanescent wave (EW) and the leakage wave (LW) from the left end of the tip for the proposed taper structures. Finally, we presented the transmission. The obtained results showed that the geometrical shape and the type of material play a crucial role for the detection of tapered fiber sensors.