Sadao Nomura

Analysis of Autostabilized Light Modulator at Microwave Frequency

The autostabilized light modulator at microwave frequency is analyzed by considering its resonance frequency shift. This analysis is based on thermal effects by heat produced in the modulator crystal by the microwave power and heat transfer from the crystal to an ambient medium. It is found that as long as the crystal temperature T does not exceed the transition temperature Tc of the crystal the state will be stable and the stability of the modulator is determined by the temperature dependence of dielectric constant and loss tangent of the crystal. The operation of the autostabilized modulator was examined by using an ADP crystal at 7GHz. This modulator is applied to the light transmission of video signals and the very successful results are obtained without any adjustments for a few days operation.

The folded-back light communication system utilizing polarization characteristics

An optical communication system based on the polarization characteristics of a single laser source is proposed. The return path is produced through mirror reflection and the mutual interference of each modulation signal transmitted between the two stations is eliminated by choosing the relative axial relations among the modulator crystals and the optical components contained in the system. The results were confirmed by telephone call experiments using ADP Pockels modulators. It was found that no mixing of signals occurred if we took the axial relations among the optical components and the modulator crystal as predicted by the theoretical results.