Comparisons and applications of fiber Bragg grating and long-period fiber grating

The fabrication,principle and characterizations of fiber Bragg grating(FBG) and long-period fiber grating(LPFG) are reported.Furthermore,the comparison and application,especially applications in sensors field at home and abroad,are presented.And an overview of the further development is also introduced.The various written technologies for different uses and the method of reducing the cladding radius to change the characteristics of fiber grating will be improved.And there will be a wide field in refractive index sensing.