Th design and evaluation of high-sensitivity lumped-element, bandpass modulators based on the integrated-optical Mach-Zehnder interferometer are presented. The optimum impedance-matched modulator response is formulated. Then a passive resonant drive circuit that achieves this response is described. In contrast to the usual baseband case, the maximum response of the impedance-matched modulator is independent of modulator length. Experimental results are given for several modulators built in lithium niobate using this circuit. Undesirable acoustic resonances are observed, and a technique for their suppression is demonstrated. >

High-sensitivity lumped-element bandpass modulators in LiNbO/sub 3/

Remote Excitation of Electron Plasma Waves by a Modulated Laser Beam

The optimum configuration of a total-internal-reflection type laser light modulator with surface interdigital electrodes has been obtained. The final specifications of the modulator were an effective half wavelenght voltage of 11.5 V, a capacitance between electrodes of 9.1 pF, and a modulation bandwidth of 400 MHz at 50 Ω load impedance. This corresponds to a remarkable safety factor of 1.7. Some effective means of eliminating harmful resonances due to acoustic waves excited in the electro-optic crystals by the interdigital electrodes were found. A practical optical communication system for transmitting catv signals in the open-air has been built and tested in the field using the modulator. In the system cross modulation and intermodulation between channels were found to be sufficiently small.

M. Katayama

Papers

Laser beam transmission of catv signals using a 400 MHz bandwidth electro-optic light modulator