Effects of fiber Bragg grating design on dual-grating demodulation performance

Abstract

Dual-grating demodulation has been both effective and simple in most fiber Bragg grating (FBG) sensors because it involves self-demodulation, and in theory, temperature effects are eliminated. Here, by applying the coupled-mode theory, influences of FBG design parameters such as grating length, refractive index modulation depth, and apodization type on the dual-grating demodulation performance are investigated. It is found that particular performance concerns and priorities can be appropriately addressed by proper selection of FBG design parameters. As an example, experiments using FBGs with properly selected parameters based on our analysis are carried out and compared with the previous experiments using available FBGs. The results show that proper FBG parameter selection can be effective for particular performance requirement.

Effect of FBG spectral parameter matching on performance of dual-grating demodulation sensors

“…The coupled-mode equation is derived from a series of Maxwell's equations and can be utilized for simulating the FBG reflectivity spectrum. In the case of a uniform FBG, when considering only the coupling between the -z and z axes and employing Euler's formula while omitting strong coupling effects, the simplified coupled-mode equation can be expressed as [12] j2 z 11 dA jAk jBke dz…”