Fiber Bragg grating FBG sensors

FBG sensors have gained considerable popularity they are simple to manufacture by UV imprinting of a grating pattern directly onto the fiber the sensor diameter is the same as the fiber diameter several different FBG sensors can be imprinted at different locations on the same fiber and can be individually addressed and multiplexed. 

When mechanical strain Ac and temperature change AT are present, the Bragg wavelength shifts with 

If the temperature is constant, only the strain effect is present and Eqn (16.1) simplifies to 

Equation (16.3) shows that the relative wavelength shift is proportional to the strain, 

Besides the center frequency shift, the FBG spectrum develops other more intricate changes representative of proximal structural damage. For example, the processing and detailed analysis of the FBG spectrum has been used to extract the effect of nonuniform strain field in the proximity of matrix cracks and delaminations [11,12]. 

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Keywords Structural Health Monitoring (SHM), Composite material, Bonded joint, Back Face Strain (BFS) technique, Fiber Bragg Grating (FBG) sensor. Single Lap Joint (SLJ)... 

Fiber optic sensors, e.g., fiber Bragg gratings (FBG) strain sensors... 

Figure 16.3 (a) Principles of fiber Bragg grating (FBG) optical sensors (b) details showing the notch in the transmission spectrum and the peak in the refiection spectrum at the Bragg wavelength [9]. 

Papantoniou A, Rigas G, Alexopoulos ND. Comp. Stmct. 2011, 93, 2163-2172. Assessment of the strain monitoring reliability of fiber Bragg grating sensor (FBGs) in advanced composite stmctures. 

Sensitivities to external fields. Sensor applications of FBGs are dependent on the sensitivities to external physical fields. The relative center wavelength shift of silica-fiber-based Bragg gratings can be written as ... 

The FBG humidity sensor is fabricated by coating suitable hygroscopic film on the surface of fiber cladding covering the Bragg grating section, as illustrated in Figure 2. The polyimide... 

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