Fabrication Of Long Period Fiber Grating Based On Infrared Femtosecond Laser

Long period fiber grating(LPFG)is a kind of transmission fiber grating with a period of hundreds of microns,which has a wide use in optical sensor and fiber optics communication.Traditional LPFG fabricated by infrared femtosecond laser is suffered from low band rejection efficiency and high insertion loss.The dissertation is focus on the LPFG fabrication with high rejection band efficiency using infrared femtosecond laser source,and the outcomes can be summarized as follows.(1)After we introduce and classify all existing fiber grating fabrication technique,we carry out comprehensive performance comparison among them and introduce the current situation and development.We put more effort on the fabrication mechanism between femtosecond laser and transparent materials,and review recent progress on the LPFG fabrication based on femtosecond laser.(2)We design and build up a fabrication platform based on femtosecond laser.The design idea and operation principle of femtosecond laser transmission are explained in details.Moreover,we develop a high precision translation platform control software,and explain the programming idea and fabrication procedure.(3)We carry out the shortcomings of traditional LPFG fabrication methods by infrared femtosecond laser and develop a two-step infrared(IR)femtosecond fiber laser exposure technique to flexibly fabricate long period fiber gratings(LPFGs)with a high peak band-rejection efficiency of 35.4 dB,insertion loss of 4.36 dB,and 3dB bandwidth of 13 nm.We experimentally investigate the impacts of fabrication parameters including laser focus location and individual exposure time with respect to the transmission spectra of LPFGs.