A 24 GHz microwave frequency divider with variable frequency dividing ratio based on a super-harmonic injectionlocked tunable optoelectronic oscillator (OEO) is proposed and experimentally demonstrated. Due to the nonlinearity of the dual-output Mach-Zehnder intensity modulator (DOMZM) and the photodiode (PD) used in the OEO loop, it can generate intermodulation components between the 24 GHz injection RF signal and the harmonics of the free-running OEO. If the frequency of any one of the intermodulation components locates at the locking range of the free-running OEO, the phase of the OEO will be synchronized to the 24 GHz injection RF signal. It realizes a microwave frequency divider. By tuning the oscillation frequency of the OEO to the second, third, or fourth sub-harmonic of the 24 GHz input RF signal, a microwave frequency divider with variable frequency dividing ratio of 2, 3, or 4 is realized. The achievable frequency dividing ratio is limited by the nonlinearity of the DOMZM and the injection RF power. A good phase noise performance of the OEO lead to a microwave frequency divider with low phase noise. The transient response of the RF phase of the output of the OEO during the process of super-harmonic injection locking is also measured.
An optical pulse generation with repetition-rate of 20 GHz based on a 10 GHz optoelectronic oscillator (OEO) is proposed and experimentally demonstrated. The combination of an optical comb generator (OFCG) and an OEO can generate an optical pulse train with the features of high repetition-rate, narrow pulse-width and low timing-jitter, simultaneously. By tuning the DC bias voltage applied on the OFCG, the modulated output light of the OFCG appears as a 20 GHz single optical pulse train which has a repetition-rate twice of the 10 GHz modulation frequency of the OFCG. It improves the repetition-rate of the optical pulse. A microwave frequency divider with dividing ratio of 2 is used to obtain an electrical signal with frequency equals to the 10 GHz modulation frequency. The output of the microwave frequency divider is fed back to drive the OFCG to form a closed OEO loop. Compared with the former ways, it eliminates the optical bandpass filter (OBPF), which improves the power efficiency of the OEO loop.