A microwave photonic filter(MPF)with reconfigurability and tunability resulting from the superposition of the transfer functions is proposed.Based on the Vernier efect between the optical frequency combs and the periodic optical filters,each comb line can be mapped into a sub-filter in the electronic field.The sub-filters are superposed to obtain the total transfer function of the MPF.By manipulating a few comb lines,we can reconfigure the passband shape,tune the bandwidth,and adjust the center frequency independently.Experiments verify that the bandwidth can be tuned from 224.8 to 674.3 MHz,and that the center frequency ranges from 1 to 4 GHz.
The relation between the phase shift and the mean optical power(MOP) output from a delay-line interferometer (DLI) port applied for phase-shift keying(PSK) signal demodulation is proven of a cosine law irrelevant to signal modulation condition.The variation amplitude of the MOP is proportional to the transition duration of the modulation pulses.This phenomenon is interpreted as the result of the statistical and waveform characteristics of the PSK.The conclusions verified by simulation and experiment are generalized to other modulation formats and then applied to phase detuning monitoring,delay time judgment of DLI,and independence of modulation data assessment.
