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We have described the main parameters which describe a fiber Bragg
grating, from the fiber itself to the different aspects of the FBGs. The
important equation is the refractive index distribution (2-11) where we
see that the grating is described with three independent functions, the
refractive index modulation amplitude, the average effective refractive index
change and the grating period. We have seen that variations of these
distributions can lead to various spectral and impulse responses. The high
sensitivity of FBGs to temperature and stress fields has also been presented.
We will see in Chapter 5 and 6 different sensing applications from point axial
or transverse stress sensors to distributed axial stress sensor and finally
temperature and humidity sensors (that profit from the swelling properties of
the coating that induce strain on the FBG).
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