Research On The Characteristics And Devices Of Microstructured Optical Fiber

In recent years,with the rapid development of multiple services such as cloudcomputing,the Internet of Things,and smart cities,the demand for high bandwidth and low latency will lead to a series of new changes in the communications industry.Among them,the development of optical network will be based on transmission and bearer function,ultra-high-speed transmission and access as the driving force,and the intelligentization of all-optical network as the goal.Relying on the National Key R&D Program Project"Microstructured Optical Fiber Integrated Devices"and the National Natural Science Foundation of China Project"New Optoelectronic Devices",this thesis focuses on the characteristics of microstructured optical fibers and the application of all-fiber structured devices.In this thesis,the properties of large mode field area,bending resistance,fillable air holes and low loss are theoretically analyzed for two types of microstructured fibers,confinement type and leaky type.And three types of devices,laser,sensor and electro-optic modulator based on microstructured fiber are prepared experimentally.The main work and innovations of the thesis are as follows:1.The characteristics of confinement microstructured photonic crystal fiber are analyzed.A large mode field area microstructured fiber with multilayer negative curvature air ring structure is proposed,and a wavelength-tunable fiber laser is built.The effects of parameters such as the number of fan-shaped rings,core and curvature radius,ring thickness and spacing on the fiber mode field area are theoretically analyzed.The results show that this fiber can achieve a bending loss of less than 0.02 d B/m in the wavelength range of 1-1.8μm,the maximum mode field area is 1358.9μm~2,and the high-to-fundamental mode loss ratio reaches 331.5.The wavelength-tunable fiber laser of hollow-core photonic crystal fiber is fused with single-mode fiber to form an interference filter,and together with polarization-maintaining photonic crystal fiber Sagnac ring to form a double filter,the wavelength tunable range of single-wavelength laser output about12 nm,the output signal-to-noise ratio is higher than 60 d B.2.The air hole filling properties of confined microstructured fibers are analyzed.Theliquid filling method of microstructured fibers controlled by capillary phenomenon is realized,and a photonic crystal fiber filled with glycerol solution is designed and fabricated.Using a thin-core photonic crystal fiber with a small diameter of 80μm,while the tapered structure generated during fusion and the adjustment of the glycerin filling amount,the strain and temperature sensitivity are increased by 0.72 pm/μεand 233.51pm/°C,respectively.And the sensor becomes temperature sensitive.The experimentally measured strain and temperature sensitivities are 2.98 pm/μεand 237.57 pm/°C,respectively.3.The sensitivity to external parameters of confinement microstructured fiber is analyzed,and a heterogeneous magnetic field intensity and temperature dual-parameter fiber sensor based on the cascade of photonic crystal fiber and Bragg grating is proposed.Magnetic fluid base fluids with different surfactants and different concentrations of magnetic particles are filled through the air holes of the photonic crystal fiber,which improves the sensitivity of the magnetic field.The experimental results show that the wave trough formed by the interference of the photonic crystal fiber can respond to the changes of magnetic field and temperature at the same time,and the highest magnetic field sensitivity is 924.63 pm/m T.The heterogeneous sensor has high stability and can effectively overcome the problem of multi-parameter cross-talk.4.The loss characteristics of leaky microstructured fibers are analyzed,and a double D-type microstructured fiber modulator is proposed.By establishing a theoretical model of the modulator and optimizing parameters such as grinding depth,spacer length and spacer thickness,the insertion loss of the designed modulator can be as low as 0.768 d B.Secondly,the electro-optic tunable characteristics of graphene are analyzed and calculated.The influence of different layers of graphene on the modulation depth is analyzed,and the influence of the thickness of the isolation layer on the extinction ratio is analyzed.Finally,a fiber graphene modulator with a modulation depth of 78.4%and a theoretical modulation speed of 15.38 GHz under a modulation voltage of 5 V is obtained.The results show that the double D-typpe structure modulator can effectively reduce the insertion loss when coupled with the optical fiber system,which helps to improve the efficiency of the modulator.5.The loss characteristics of leaky microstructured square fiber are analyzed,and a modulator based on the fiber is proposed.Firstly,the effects of half-length fiber pitch,radian radius,numerical aperture and spacer thickness on mode loss are analyzed.Theoretically,the minimum mode loss of the square fiber modulator is 0.0179 d B/mm,and the mode field mismatch loss is 7.506%.Secondly,the processing techniques of microstructured fibers such as grinding method,hydrofluoric acid etching method and femtosecond laser cutting method are studied.And electrode growth,graphene film transfer and growth methods are explored.Finally,a square fiber electro-optic modulator test system is built.The experimental results show that the minimum insertion loss of the modulator is 0.21 d B,and the modulation voltage is less than 10 V.