Phase shift keying using optical delay modulation for millimeter-wave fiber-optic radio links

We propose a novel phase shift keying technique that uses optical delay modulation for fiber optic radio links. Using only a 2/spl times/1 switch and a delay line, this technique enables modulation of a millimeter-wave carrier at bit rates of several gigabits per second or higher, where high-speed devices are not needed. Binary phase shift keying (BPSK) was experimentally demonstrated, 2-Gb/s data signal on a 40-GHz carrier was transmitted over a 5-km optical fiber without any error. The coherent crosstalk noise, due to insufficient extinction ratio of optical switches, was evaluated. The BPSK modulation technique can he extended to multiphase shift-keying modulation.