Integration Method of Analysis for Intra-grating Sensing with a Chirped Fiber Bragg Grating

Abstract

The intra-grating temperature profile of a chirped fiber Bragg grating was determined using integration of the changes in power reflectance spectra whilst it was subjected to a nonuniform temperature distribution.

Localized strain measurements using an integration method to process intensity reflection spectra from a chirped FBG

“…From the CFBG reflection spectra, the strain distribution was deduced using our integration method [9]. The use of finite element method (FEM) modeling confirms the strain profiles determined.…”

“…Fig. 1(b) shows the schematic of the mechanical and optical arrangements, the latter being similar to that used previously [8][9][10]. The CFBG sensor was monitored in reflection using an Er 3+ broadband light source via a 3-dB 1550-nm coupler.…”

“…Fig. 3 shows the strain profiles, extracted from the averaged CFBG spectra, as a function of position along the grating, obtained using the integration of difference technique [9][10], for various loads. A strain error of approximately 170 µε has been estimated, due primarily to variations in the applied load.…”

“…Prior work on determining intragrating temperature profiles using a hypothesis profile and employing transfer matrix or Fourier grating models require the shape of the temperature profile to be conjectured and programmed [7][8]. Recently, we applied an integration method to operate only on reflectance spectra from a chirped fiber Bragg grating (CFBG) without the requirement for prior knowledge of the shape of a hypothesis temperature profile [9]. In the method, which has been used to analyze a temperature hot-spot [9] and a temperature step [10], the known chirp of the grating provides the means to associate each wavelength in the FBG spectrum with a location along the sensor [9].…”

“…Recently, we applied an integration method to operate only on reflectance spectra from a chirped fiber Bragg grating (CFBG) without the requirement for prior knowledge of the shape of a hypothesis temperature profile [9]. In the method, which has been used to analyze a temperature hot-spot [9] and a temperature step [10], the known chirp of the grating provides the means to associate each wavelength in the FBG spectrum with a location along the sensor [9].…”