The Spectral Characteristics Of Cascaded Long Period Fiber Grating And Applied Research

In this dissertation, the review about fiber bragg grating is presented. Then the progress and values of the research into long-period fiber grating are discussed.Based on classical coupling-mode theory and fiber bragg grating theory, the parameters and the shape of cascaded long-period fiber gratings are calculated and simulated.In this dissertation the creative idea on the structure of cascaded long-period fiber gratings is put forward ,the parameters and the shape decided by the structure of cascaded long-period fiber gratings and phase shifted long-period fiber gratings are systematically analyzed and are simulated through software Matlab. By contrasting the parameters and shape of the two gratings, the differences between them are pointed out. The basis of theory /which can be applied in the use of wavelength multiplex and de-multiplex system and transducer, is offered.Finally, wavelength multiplex and demultiplex system including its components is introduced. The cascaded long-period fiber gratings theory can be applied in the two components of this wavelength multiplex and de-multiplex system :one is erbium-doped fiber amplifier (EDFA) , the other is comb-filter fiber. These two applications are all simulated through software Matlab and the main limitation of erbium-doped fiber amplifier (EDFA) can be rectified through application of the cascaded long-period fiber gratings theory in equal aggrandizement of different lightwaves .Therefore the possibility of application of cascaded long-period fiber gratings in these two components is proved. And because of its special construction, cascaded long-period fiber gratings has the great future in the use of transducer.