Study On Tolerance Tolerance Of Arm Length Difference Of Microwave Photonic Filter Based On Sagnac Ring

With the demand of Internet traffic growing exponentially, the single wavelength transmission rate of fiber core network has been more than 100Gb/s per fiber, which is being developed to 400Gb/s and Tb/s. So the requirements to the performances of filters become more stringent. A Sagnac ring based microwave photonic filter has been widely used due to the advantages of simple structure, polarization independence, high side lobe suppression, stable performances, easy to be tuned, etc. In practical applications, the influences of temperature and other factors on the Sagnac ring based microwave photonic filter are studied extensively. However, the error of fiber length difference（?L′） has not been studied in detail.In this thesis, we mainly study four kinds of interference comb filter, especially a FBG based and a Hi Bi-PCF based Sagnac ring filter. The main works and innovations are as follows:（1）Studies about a FBG based Sagnac ring filter. The theoretical models between ?L′ and ?λ′ is established using Jones matrix theory and verified by Matlab numerical simulations. The theoretical and simulation results show that the tolerance of ?L′ is independent of ΔL. When set Lg)= 2mm,Λ = 535 nm and neff= 1.45, whatever ΔL is, the tolerance of ?L′ is 0.1μm, and the power loss is 8d B.（2） Studies about the tolerance of error of fiber length difference in a Hi Bi-PCF based Sagnac ring filter. The influence of the key parameter of the filter system on the system performance is analyzed. The theoretical models between ?L′ and ?λ′ is established using Jones matrix theory and verified by Matlab numerical simulations. The theoretical and simulation results show that the tolerance of ?L′ is independent of ΔL, and when set k=0.5, θ = π?2, Δn = 0.005 and L=5m, the tolerance of ?L′ is 80μm.（3）Studies about a Mach-Zehnder interference based microwave photonic filter. The influence of the key parameter of the filter system on the system performance is analyzed. The influence of ?L′ on the system performance is quantitatively studied. The theoretical and simulation results show that when set k₁= k₂= 0.5、?L = 1mm, the tolerance of ?L′ is 0.4μm.（4） Studies about an F-P interference based microwave photonic filter. The influence of the error in the length of F-P on the system performance is analyzed. The theoretical expression of the wavelength of filter spectral shift and power loss at the peak value is derived by using the Jones matrix theory and verified by Matlab simulation. The theoretical and simulation results show that when set L=0.3mm, θ = 0°, R=0.25 and n_eff=1.45, the tolerance of ?L′ is 0.1μm.This study can be used in the design and manufacture of this kind of interference filter. It can also be used in quantitative calculation of the variation of fiber length difference（ΔL） caused by the external factors in the optical sensing system and optical communication system.