All-optical logic gate based on MMI (Multi-Mode Interference) is proposed in this paper. Different from other methods, MMI efffect is utilized for the logic functions including AND, OR, NOR, and XOR. All-optical logic function is realized at specific output waveguides in accordance with the control signal condition.
The refractive index and the film thickness were measured by the prism coupler, and GeO2 and P2O5 concentration were analyzed by EPMA (Electron Probe Micro Analysis) according to the torch inclination angle and the distance between torch and substrate. As the torch angle was steeper, the thickness and the GeO2 concentration were increased, and the P2O5 concentration was decreased for the angle greater than 45o.
Stimulated Brillouin Scattering, observed in an optical transmission system using fibre lasers as signal sources, was suppressed by external phase modulation. The threshold power of SBS in a single mode fibre with 8.3-micrometers diameter was as low as 2 dBm due to a narrow spectral linewidth of a fibre laser. At 20 MHz phase-modulation, modulation voltages above 5.3V suppressed the first order Stokes more than 25 dB. RF spectrums of the fibre laser phase-modulated at or above 5.3V showed multiple sets of sideband components higher than the carrier frequency component in amplitude. The minimum spectral bandwidth of a fibre laser with 20 kHz bandwidth was broadened to 120 MHz at this modulation condition. The results signified broadening of the effective spectral linewidth of the fibre laser by phase modulation.
An InGaAsP/InP variable power splitter utilizing the multimode interference (MMI) and the linear electro-optic (LEO) effect is designed and analyzed. The splitter consists of two MMI waveguides and phase-shifting waveguide section between them. The input MMI waveguide acts as a 3-dB splitter for the TE input signal. In the phase-shifting waveguides, the relative phase of split input signals is changed by using the LEO effect. The output MMI waveguide combines the phase-modulated signals at output ports. Depending on the amount of phase change induced by reverse bias voltages of 0 approximately 2.5 V, the splitting ratio varies from 100(DOT)0 to 50:50 continuously.
The present paper proposes the retrofit use of dynamic restrainers at the expansion joint for preventing the collapse of bridges in the event of a severe earthquake. The proposed dynamic restrainer consists of a nonlinear viscous damper and an elastic spring connected in parallel. Two-dimensional nonlinear finite element analysis using bilinear hysteretic models for RC bridge substructure joints and nonlinear gap elements for expansion joints is performed on example bridges with one or two expansion joints. The numerical simulation study indicates that the dynamic restrainers are substantially effective in reducing the relative opening displacements and impact forces due to pounding at the expansion joints. It is also found that the dynamic restrainer can be installed at expansion joint in abutment as well as between adjacent bridge frames to avoid a possible increase of ductility demands in the bridge substructures.
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