ABSTRACT
Nowadays, newly produced materials are increasingly smart in the sense that they embed sensors and/or metrological tools able to provide real-time information about
4.1 Introduction ....................................................................................................69 4.2 Fundamentals on FBGs .................................................................................. 70
4.2.1 Basic Principle of Uniform FBGs ....................................................... 70 4.2.2 Temperature Sensitivity of Uniform FBGs......................................... 72 4.2.3 Axial Strain Sensitivity of Uniform FBGs ......................................... 73 4.2.4 Pressure Sensitivity of Uniform FBGs ............................................... 76 4.2.5 Transverse Strain Sensitivity of Uniform FBGs .................................77 4.2.6 Other Kinds of Fiber Gratings of Interest to Be Embedded into
Composite Materials ........................................................................... 78 4.3 Demodulation Techniques Used to Retrieve the Bragg Wavelength Shift ..... 81
4.3.1 Techniques Based on Wavelength Detection ...................................... 81 4.3.2 Reflectometric Demodulation Techniques .......................................... 82
4.4 Discrimination between Temperature and Strain Effects .............................. 83 4.4.1 FBG Pairs with One of Them Embedded into a Glass Capillary ......85 4.4.2 FBG Pair Comprising Type I and Type IA FBGs ..............................86 4.4.3 Weakly Tilted FBG .............................................................................86 4.4.4 Comparison of Performances .............................................................87
