Sensing Properties of Long Period Fiber Grating Coated by Silver Film

In long period fiber gratings (LPFGs), the fiber modes guided by the core layer can excite surface plasmon resonance (SPR) in the metallic thin-film coated on the cylindrical surface of fibers. In this letter, the LPFG-based fiber optic SPR sensor is analyzed numerically by unconjugated form of coupled mode method.

According to the mode analysis, the EH modes can couple with surface plasmon mode and are suitable for refractive index sensing application. In wavelength interrogation, the transmission dip caused by SPR is sensitive to the environmental refractive index. The sensitivity of the sensor achieves 1660 nm/RIU in the aqueous solution.