Direct modulation of an opto-electronic oscillator: Towards radio over fiber

This paper presents a new technique for direct frequency modulation of an optoelectronic oscillator (OEO) that can be applied to radio over fiber technology. The method is based on an optically controlled phase shifter. The control element is a semiconductor optical amplifier (SOA) which is inserted in the OEO loop. By this way a voltage controlled OEO (VC-OEO) is realized. It is then demonstrated that a modulation index of 5.45 can be obtained by applying to the SOA a driving sine signal with 360 mV amplitude and 1 kHz frequency.