Single-mode Hollow Bragg Fiber For High Power Femtosecond Pulse Transmission

The singer-mode hollow Bragg fiber is a novel photonic bandgap fiber with one dimensional photonic crystal cladding.Comparing to traditional optical fibers,its structure characteristics,light-guiding mechanism and propagation properties are different,own some prominent advantages include single-mode transmission characteristics,low loss,low non-linear effects and controllable dispersion characteristics.There are great potential in optical communication,optical fiber sensing technique and femtosecond pulse transmissionDue to the femtosecond pulse with high energy density cannot be transmitted in traditional optical fibers,this paper devotes to design the single-mode hollow Bragg fiber for femtosecond pulses transmission.First,the cladding materials are prepared based on one-dimensional photonic crystal's bandgap characteristics.Then,the fiber structure parameters and transmission properties are analyzed by using the optical software FDTD Solutions.It can be seen by full bandwidth scanning that the fundamental mode bandwidth achieve around 100nm which can transmit 100 fs optical pulses,and transmission loss can be lower than 2.3dB/km.And then,summarize the dispersion accommodation technique of single-mode hollow Bragg fiber through bringing defect layer in cladding layer.At last,the hollow single-mode Bragg fiber with zero dispersion wavelength or large negative dispersion at 1.55pm is designed.The main contents are as follows:1.Research the hollow single-mode Bragg fiber's bandgap characteristics using transfer matrix method,It discusses the effect of the thickness of the high and low refractive index layer,the refractive index ratio and the lattice period on the bandgap characteristics.The conditions of single-mode transmission is studied and analyzed in depth,and the design principles of the hollow single-mode Bragg fiber was summarized.2.It discusses the effect of the core radius,refractive index ratio and lattice period on the fiber mode by using the optical software FDTD Solutions.The transmission characteristics of fundamental mode are investigated,and the bandwidth,dispersion and loss of fundamental mode are discussed.On the basis of the above work,a kind of hollow single-mode Bragg fiber for high power femtosecond pulse transmission is designed,but it has great positive dispersion at 1.55?m.3.The single-mode hollow Bragg fiber with great positive dispersion cannot be used for long distance transmission,so the effect of overlap between fundamental mode and defect mode are analyzed theoretically,and the dispersion accommodation technique of single-mode hollow Bragg fiber based on defect layer is summarized.As a result,we obtain a kind of single-mode hollow Bragg fiber with wide bandwidth,low loss and zero dispersion wavelength or large negative dispersion at 1.55p?m.