RF output-power enhancement by optical-pulse compression in photonic-based RF generation

In photonic-based RF generation, the RF output power is limited by the average optical power to the photodetector (PD). It is known that the RF output power is enhanced by use of a narrow optical pulse at the photodetector, whereas the average power to the photodetector is the same. In this paper, we propose to use optical-pulse compression in a standard optical fiber in order to enhance the RF output power. We use an optical two tone, or optical pulses generated with a Mach-Zehnder modulator (MZM), as an optical-pulse source. In numerical simulation of the Mach-Zehnder modulator pulse, a maximum RF gain due to optical-pulse compression of 8.0 dB is obtained. In a 20-GHz RF generation experiment with a standard single-mode fiber and a Mach-Zehnder modulator pulse, an RF gain of 6.6 dB was obtained with a fiber length of 7.5 km and a launched average power to the fiber of 20.0 dBm. Furthermore, we found that 50 GHz, 75 GHz, and 100 GHz generation with RF gain is possible with realistic optical power if non-zero dispersion-shifted fiber is used as the transmission fiber, whereas highly nonlinear fiber is necessary for 300-GHz RF generation.