Dispersion characteristics in metal coated long period fiber gratings

Based on the coupled mode theory, the influences of material dispersion on the spectral characteristics of the gold coated long-period fiber grating (LPFG) are studied theoretically. The theoretical simulation indicates that there are a series of de-dispersion grating periods, under which the electrical tuning characteristics of the tunable loss filter can be greatly improved. Besides, the spectral characteristics of metal coated LPFG sensor with sensitive film are investigated. The result shows that the resonant wavelength of the cladding mode shifts toward shorter wavelength direction when gold dispersion is taken into consideration. Also, the sensitivity of gold coated LPFG with sensitive film is studied in consideration of the dispersion. Simulation results show that the resolution of this sensor with optimal parameters to the sensitive film refractive index is 7×10^-7.