The Research On Microwave Photonic Filtering Technology Based On Stimulated Brillouin Scattering

Microwave photonic filters(MPF),in which the microwave signal is encoded into the optical domain and filtered by photonic techniques,are highly desired in microwave photonics for the excellent properties such as low loss,large tunability as well as anti-electromagnetic interference.Stimulated Brillouin scattering(SBS)has become one of the mainstream schemes to construct MPFs as it can realize single-passband response,high selectivity with good reconfigurability.The structure design,performance simulations and experimental verification of the reconfigurable MPF based on SBS is studied in this dissertation.(1)With the coupled wave equations illustrating the SBS dynamics,the interaction principles among stokes and pump wave as well as acoustic wave in fiber have been analyzed.Then a simplified version is inferred under steady-state conditions and the numerical solution approach is also given.Based on that,the analytical model of SBS-MPF is established.(2)A dual-stage SBS-MPF utilizing pump-splitting scheme is proposed,which can effectively relieve the restriction of the gain saturation effect on the input dynamic range and selectivity.The effect of the fiber length and pump optical power as well as input signal optical power on the key performance indexes of the proposed MPF has been deeply analyzed.The results show that when the operation parameters are optimized,for signal input optical levels between-60 dBm and-20 dBm,the selectivity of the dual-stage MPF is maintained >49 dB.And the 20-dB shape factor(SF)is <1.7 during the bandwidth is reconfigured from 50 MHz up to 200 MHz.These indexes are superior compared to the conventional sing-stage scheme.Meanwhile,the noise performance of the proposed device has also been analyzed by simulation and the results indicate that the performance of the dual-stage filter is not seriously degraded compared to the single-stage scheme.(3)A platform to measure the comprehensive performance of the SBS-MPF has been constructed,and the effect of the input signal power and pump power on the amplitude response and noise performance of the proposed SBS-MPF has been experimentally analyzed.It proves that when the operation parameters are properly selected,the dual-stage SBS-MPF can realize a single-passband response with a selectivity of >49 dB and a passband ripple of <1.3 dB simultaneously for signal input optical levels between-60 dBm and-20 dBm.Meanwhile,the bandwidth is reconfigured from 50 MHz up to 200 MHz and the SF is as low as 1.2 for 200MHz-case.These indexes are superior compared to the conventional sing-stage scheme.Meanwhile,the noise performance of the dual-stage filter is not seriously degraded compared to the sing-stage scheme.In general,these are in accordance with the simulation results.