Research On Functional Polymer Optical Fiber Devices

After decades of development, there are more and more species of optical fiber devices, and become a research category by its own, these devices are widely used in the field of communication and sensing. Now days as the growth of the information technology, more functionality and better performance of fiber optic devices are demanded. Polymeric materials is low cost and can be easily processed, which also have excellent optical properties due to the special structure and functional side chain, making it have huge potential applications in integrated optics, nonlinear optics, adjustable lasers, sensors and other fields. So polymer optical fiber devices have been of great concern in recent years. The purpose of this thesis is to introduce a new polymer material with good optical quality, and use the material to develop basic optical fiber devices, like Eu(TTA)3Phen solution-filled fiber amplifier, intensity/polarization modulation based on azopolymer-silica compound fiber and polymer optical fiber Bragg grating。The contents of the thesis are as follows: A liquid-core fiber doped with rare earth was fabricated by filling the solution into silica capillaries. The absorption and emission spectra of the optical fiber with Eu(TTA)3Phen solution were studied. The fluorescent lifetime of Eu(TTA)3Phen is0.543ms, there is a strong absorption peak at a wavelength of355nm, but the emission peak is at613nm. By theoretical simulation of the Eu3+doped fiber amplifying characteristics, we find that the optimum gain length of optic fiber with liquid core is much smaller than silica fiber, only at the order of one percent. And this result provides a theoretical basis for the production of rare earth doped polymer optical fiber. From the theoretical analysis the amplification influence by the concentration, parameters of fiber structure, properties of rare earth, and provide guidance for the design and production of high-performance liquid core optical fiber amplifier. Then the amplification characteristics of the liquid core optical fiber with Eu(TTA)3Phen was measured experimentally. Results show that the liquid core optical fiber with a length of8.1cm, a doped concentration of0.8wt.%, and pump power of203mW, a gain of8.2dB was achieved for the signal light of613nm. A compound fiber with azobenzene polymer as the cladding and etched silica fiber as the core was fabricated. The properties of the propagating light in the compound fiber affected by the parameters of fiber and properties of the coated polymer was theoretical analyzed. Both fluoride azobenzene polymers and azopolynmer contain polyhedral oligomeric silsesquioxanes (POSS) were overlaid on the etched silica fiber. Based on the azobenzene polymer light-induced refractive index change and the light-induced birefringence, dynamic modulation of the power and the polarization state transmitted in the optical fiber by external light were achieved. Experimental results show that the reversible modulation and good reproducibility. With irradiation of435nm polarized light at0°, Poss contained azopolymer-silica compound fiber can achieve a phase change of360°, it showed a large range of modulation. Azopolymer-silica compound fiber provides a new way for manufacturing all-optical devices and functional fiber devices.A few-mode polymer optical fiber (POF) with highly photosensitive core doped with benzil dimethyl ketal (BDK) was fabricated and used for writing Bragg grating by the modified Sagnec interference method. The coupled mode theory was used to analyse the coupling of guided modes in the few-mode POF, and then the response of temperature and strain of the few-mode POF Bragg grating was numerical simulated. As the silica optical fiber have almost the same thermo-optic coefficient for the core and the cladding material, the few-mode fiber Bragg grating in silica fiber have same strain response and temperature response for all guided modes. But for the POF, which has a huge differenence in the thermo-optic coefficient of the core and cladding materials, there are same strain response dependence but different temperature dependence for all the guided modes in the few-mode POF Bragg grating. Thus a single few-mode POF Bragg grating can be used to measure the temperature and the strain simultaneously. Finally, a few-mode POF Bragg grating with BDK doped was used for experimental verification. The experiment results shows the temperature sensitivities is-98pm/℃、-103pm/℃、-105pm/℃and-111pm/℃, and the strain sensitivity is1.193pm/με、1.189pm/με、1.186pm/μεand1.163pm/με.According to the theoretical analysis, the temperature and strain sensitivities can be further improved by faibricating a few-mode POF Bragg grating which has a larger difference of thermo-optic coefficient between the materials of the core and the cladding.