Reciprocating optical modulation for millimeter-wave generation by using a dual-section fiber Bragg grating

We investigated reciprocating optical modulation (ROM) for millimeter-wave generation. The system was composed of an optical phase modulator and a pair of optical filters. A lightwave modulated by V-band millimeter waves was obtained from a 5-GHz electric signal. The spectrum linewidths of the generated 60-GHz millimeter wave was smaller than 300 Hz. By using mode-coupling equations, the spectra of output lightwave were theoretically calculated. It was shown that the spectra depend on the optical path length between the two optical filters, so that harmonic generation and mixing with baseband signals can be obtained simultaneously. Intensity modulation of the generated millimeter wave was demonstrated by applying a baseband signal to the modulator without using another electric or optical modulator.