Characteristics of metal-coated long-period fiber gratings

Long-period fiber gratings (LPFGs) are usually used as the spectrally selective loss filter in optical fiber communication networks and sensor systems. In this paper, we investigate the characteristics of a tunable filter based on metal-coated long-period fiber grating. By applying different current to the metal coat, the resonance wavelengths can be tuned, with the spectrum shape changing little. The experimental results and theoretical analysis indicate that the metal-coated LPFGs may find interesting applications such as tunable and adjustable filters.