We propose and experimentally demonstrate a scheme of high-Q microwave photonic filter （MPF） using the techniques of self-phase modulation （SPM） spectrum broadening and third-order dispersion （TOD） compensation. The optical pulses from a mode-locking laser are spectrally broadened by the SPM in the highly nonlinear fiber. A wideband optical frequency comb with 365 spectral lines within 10-dB power variation from the highest spectral power is obtained. By applying a cubic phase modulation via a waveshaper, the effect of TOD which broadens the MPF passband is eliminated. The final implemented MPF has a Q-value as high as 296 and a tuning range of 700 MHz.
The principle of error vector magnitude （EVM） against modulator nonlinearity for vector modulation signal （VMS） transmission in radio-over-fiber （RoF） systems is theoretically and experimentally investigated. A highly linear modulation scheme is proposed and demonstrated using a single-drive dual parallel Mach–Zehnder modulator （MZM）. This method improves EVM performance and enlarges the linear input dynamic range of the VMS transmission. An index of maximum allowable input power difference （MAIPD） that reflects the difference of upper input power limits between these two schemes is measured. An EVM limitation of 5% MAIPD has 5 dB. Both 16and 64-QAM results indicate that the proposed scheme supports VMS transmission better than the MZM one.
