The technical principle is to use ultraviolet laser beam to illuminate the optical fiber, and the refractive index of the fiber core in the illuminated section changes periodically. This refractive index change area is called fiber grating. The fiber grating is essentially a narrowband filter or reflector formed in the fiber core, which selectively reflects the incident broadband light and reflects a narrowband light modulated by the grating area. The transmitted light continues to be transmitted along the optical fiber. Each fiber grating has a corresponding central wavelength, and the central wavelength value is in a coefficient relationship with the measured physical quantity at the location of the fiber grating.