Research On Microwave Photonic Filter Based On Multi-wavelength Fiber Laser

Photonic Microwave Filter（PMF）is an important branch of the Microwave Photonics.The PMF which can filter microwave signals directly in optical domain meets the growingdemand for bandwidth of today’s society because it can overcome the electronic bottleneck.Multi-wavelength fiber laser which is narrow line-width and good tenability is very suitablefor constructing PMFs, and PMF based on multi-wavelength fiber laser will be an importantdirection in the PMF field.This paper mainly concentrates on simulation and experimental research on the design oftap coefficients and structure. The main content and innovation points are as follows:1) The development of microwave photonics in recent years and the hot spot in this field isdescribed briefly. Multi-wavelength fiber laser and microwave photonic filters arereviewed. The study of microwave photonic filter status at home and abroad isemphatically introduced.2) The principle of microwave photonic filter is introduced and its transfer function isderived. The theory of the phase modulation to intensity modulation conversion whichcan be used to design a band-pass PMF easily is described. Common PMFs arepresented by classification.3) The traditional methods to design microwave photonic filter taps are analysed andcompared and a new method which uses window function is proposed. Throughsimulation analysis we find that the new method can not only design a low-pass filter,but also can easily design a band-pass filter, which greatly simplifies the design process.On this basis, the various factors，such as the tap coefficients, the number of tap, tapprecision and delay between the adjacent taps, that affect the performance of the PMFare simulated and analysed.4) The multi-wavelength fiber laser and the birefringent optical loop mirror are studiedtheoretically and experimentally. A new tunable microwave photonic band-pass filterwhich is low cost, high side-lobe suppression, tunable and simple structure is designedusing multi-wavelength fiber laser and birefringent optical loop mirror combined withthe phase modulation to intensity modulation conversion technology. By simulation wefind that the tuning range of the PMF is7.66GHz and the side-lobe suppression ratio is33dB which is higher than the PMF without birefringence fiber loop mirror whoseside-lobe suppression is22dB.