The behavior of a temperature self-compensating, fiber, long-period grating (LPG) device is studied. This device consists of a single 325-μm-period LPG recorded across two sections of a single-mode B-Ge-codoped fiber—one section bare and the other coated with a 1-μm thickness of Ag. This structure generates two attenuation bands associated with the eighth and ninth cladding modes, which are spectrally close together (∼60 nm). The attenuation band associated with the Ag-coated section is unaffected by changes in the refractive index of the surrounding medium and can be used to compensate for the temperature of the bare-fiber section. The sensor has a resolution of ±1.0 × 10-3 for the refractive index and ±0.3 °C for the temperature. The effect of bending on the spectral characteristics of the two attenuation bands was found to be nonlinear, with the Ag-coated LPG having the greater sensitivity.
© 2003 Optical Society of America
Thomas Allsop, Ron Neal, Domenico Giannone, David J. Webb, Des J. Mapps, and Ian Bennion, "Sensing Characteristics of a Novel Two-Section Long-Period Grating," Appl. Opt. 42, 3766-3771 (2003)