Dispersion characteristics in metal coated long period fiber gratings

Abstract

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 LPFG loss filter can be greatly improved. While heating the metal coating of LPFG, this LPFG loss filter not only retains the spectral shapes of the stop-band, but also has stable optical filtering percent. Further, the spectral characteristics of metal coated LPFG sensor with the sensitive film are investigated. The result shows that the jumping region of the response of the resonant wavelength varies with the sensitive film thickness is broaden when the metal dispersion is taken into consideration. Also, the sensitivity of gold coated LPFG with the sensitive film is studied in consideration of the dispersion. Simulation results show that the sensitivity and the resolution of the refractive index of this LPFG sensor with optimal parameters are available to 30 and 7 × 10−7 respectively. In addition, the contour of sensitivity is depict to obtain accurate parameter combinations for designing high sensitivity LPFG sensor.