SBS-based Microwave Photonic Filter Design Using Directly Modulated Pump And Its Applications

The development of 5G communication technology meets the business requirements for larger bandwidth,higher reliability,lower latency.With a sharp increase in quantity of devices connected to the network,it is of great urgency to improve network capacity.Due to the tremendous superiority in bandwidth,a mm-Wave based wireless access scheme becomes an excellent choice of improving network capacity.However,generating and processing of high frequency mm-Wave signals are difficult for electronic devices,microwave photonic schemes show more advantages.As a typical application of microwave photonics,microwave photonic filters have attracted many attentions.Relatively low Brillouin threshold power,ultra-narrow natural Brillouin linewidth,high Brillouin gain make stimulated Brillouin scattering(SBS)an optimal scheme for implementing microwave photonic filters.By precise control of pump power spectrum,arbitrary-shaped microwave photonic filters have been achieved.On the basis of analyzing chirp effect in direct modulation carefully,corresponding relations between injection current and pump power spectrum of the output light have been deduced and validation of the relations has been verified by both software simulation and experiments.Based on the relations,a ~860MHz wide rectangular microwave photonic filter has been achieved and the influences of fiber length and average current waveform repetition period on filter performance are studied by experiments as well.By measuring the in-band ripples and gain profiles,optimal performance has been achieved with the average waveform repetition period of the driving current ranging from 9 to 13 ns and it has nothing to do with fiber length.Therefore,a general guideline of SBS-based microwave photonic filter design using a directly-modulated pump is proposed and potential application values of this filter in short fiber or waveguides have been discovered.This work points the orientation for miniaturization and integration of microwave photonic filters.