Output power enhancement in photonic-based RF generation by optical pulse compression with a constant dispersion fiber

Abstract

Microwave and millimeter-wave generation based on photonic technology [1-3] is promising for many applications. In this method, the RF output power is limited by the maximum average optical power to the photo detector (PD). Therefore, photodiodes with high optical power handling are necessary if high RF output power is required. Hirata et al. reported that if the optical pulse width to the PD is narrower, though the average power to the PD is the same, the RF output power is enhanced since the fundamental frequency component included in the PD input is increased [4]. Kuo et al. theoretically analyzed this phenomenon with a phase-locked optical frequency comb with equal amplitude [5] and derived that the RF power is enhanced by 6 dB when the number of comb lines is increased from two (optical two-tone) to infinite (zero pulse width). So far, 100-GHz [5] and 160-GHz [6] RF generations have been reported by using short optical pulses to the PD. The use of an optical frequency comb and a spectral pulse shaper enables us to shorten the optical pulse width. Recently, we have proposed a new simple approach that utilizes an optical pulse compression in a constant dispersion optical fiber, which is performed by the combined effects of group velocity dispersion and self phase modulation [7, 8]. The optical pulse width can be shortened by properly adjusting the fiber length and launched power to the fiber in accordance with the fiber dispersion and pulse repetition frequency. In this talk, we present operational principle of the proposed method, results of simulation and experiment of 20-GHz RF generation using a standard single-mode fiber, and the simulation results for investigating the possibility of 100-GHz and 300-GHz RF generation.