Study On Photosensitive Erbium Doped Optical Fibers And Bragg Grating-Assisted Coupler For Add/Drop Filters

In recent years,a focus on the study of optical fiber communication is AON,and it is the necessarily developing result for optical network.Rare earth doped fibers and all fiber optical add/drop filters become two of the Key Technologies in AON because of their excellent performances.Under the supports of national 863 high technology program China "Rare-earth doped fibers","Novel special optical fibers" and the national natural science foundation of China(60837002),design and fabrication of photosensitive erbium doped optical fibers(PEDFs) and Bragg grating-assisted coupler for add/drop filters are deeply discussed in this thesis.And the main achievements are listed as follows:1.An accurate finite element modal with perfectly matched layer(PML) boundary condition(1^stPML+FEM) is proposed and demonstrated,which can be used to solve the solution of modes of fibers with arbitrary nohomogeneous and anisotropic refractive indices distribution.2.Considering the processes of fabricating rare-earth doped fibers with MCVD method combined with solution doping technique(SDT) and the requirements of fabricating high consistency germanium doped photosensitive fibers,the reasons of conflicts between the high consistency aluminum doping and high consistency germanium doping in the fiber core simultaneously are detected.In order to fabricate PEDFs with good photosensitivity and gain performance simultaneously, two kinds of new methods are proposed and demonstrated,which are multi-core design method and double-layer core design method.The mode field distributions along with their propagation constants for modes of seven-core PEDFs and DLC-PEDFs are calculated separately using 1^stPML+FEM and samples of seven-core PEDF and DLC-PEDF are fabricated by MCVD method combined with SDT.Testing results show that PEDFs with high quality can be obtained using multi-core design method or double-layer core design method.3.The scalar approximation coupled-mode equations are deduced,which can be used to analyze all kinds of Bragg grating-assisted coupler for add/drop filters and the equations' coefficients have definite physical meaning.Using the unified coupled-mode equations,three kinds of Bragg grating-assisted coupler for add/drop filters,named "FBG-frustrated coupler","FBGs-reflecting coupler" and "FBG-assisted coupler",are investigated systemically.Samples of FBGs-reflecting coupler and FBG-assisted coupler are fabricated and tested in details.And the experimentally measured results are in good agreement with the numerical calculations.Using the sample of FBG-assisted coupler,a wavelength de-multiplexing transmission experiment is done in 8.5Gbps and 10Gbps system with NRZ optical signals.And experimental results show that the sample filter basiclly realizes the function of wavelength de-multiplexing.