Researches On LPFG And ULPFG Fabricated By CO₂Laser

As a kind of significant passive photonic components, optical fiber grating has beenwidely applied in optical fiber communication and optical fiber sensing due to its uniqueadvantages and properties. The fabrication technique of fiber grating has been constantlyenriched, improved and developed. Recently, the widely applied UV exposure methodutilizing phase mask has achieved the industrial mass production of fiber Bragg grating,but the UV exposure method relies on the photosensitivity, is restricted to the fiber type.CO2-laser pulses writing method, using the principle of thermal processing to achieve thelocal refractive index modulation in optical fiber, is not subject to restrictions on the typeof fiber, does not require hydrogen loading, annealing on optical fiber, and has beenconcerned widely. Our research group has studied the theoretical foundations of CO2-laserpulses writing technique in depth. On this basis, this paper research the fabricationtechnique of long period grating and ultra-long period grating using CO2-laser pulses Thespecific research work of this paper can be summarized as follows:Firstly, the development history and fabrication technology of the long-period fibergrating and ultra-long-period fiber grating are introduced. And the applications in sensingareas are also stated.Secondly, the formation mechanism of CO2-pulse laser writing technique is studiedin detail. Base on the formation mechanism, the coupled local-mode theory of optical fibergrating which developed on the basis of the coupled-mode theory are adopted as thetheoretical analysis method of this paper.Then, the fabrication technology of CO2-pulse laser writing technique is identifiedand the platform system is built. The influencing factors of fiber grating fabrication whichconsists of scanning time, laser power, number of scan, grating period is analyzedFinally, long-period fiber grating and ultra-long-fiber grating are written in bothsingle mode fiber and grapefruit-type photonic crystal fiber, then the sensingcharacteristics are analyzed. The temperature, axial stress and refractivity sensingcharacteristics are comparative analyzed.