Study On The Sensing Techniques Of Polarization-Maintaining Fiber Bragg Grating

As a new technology in sensing, fiber Bragg grating (FBG) has many advantages, to which the common sensors are inferior, and it has wide applications in the fields of architecture, bridge, aviation and spaceflight, etc. Now the FBG sensors in operation mostly make use of its sensing characteristics of axial stress and strain. Standard FBG is only sensitive to temperature and axial strain, and unsensitive to radial strain which is also very important, such a disadvantage limits the applications of the standard FBG sensors. A type of polarization-maintaining FBG (PMFBG) weight sensor was adopted in this thesis, and it can simultaneously measure the changes of both temperature and transverse load.The theoretical analysises have shown that the two resonant wavelengths of PMFBG have different sensitivities to the changes of temperature and transverse load, and the changens of temperature and transverse load can be simultaneous measured using PMFBG sensing element. The inherent birefringence was simulated and analyzed using the software of ANSYS, and the structure factors that influenced the inherent birefringence were studied. These analysis results can be used as references supplied to the structure optimization of polarization-maintaining fiber.The PMFBG sensing experimental systems of temperature, axial strain and transverse load were set up, respectively, and the corresponding experiments were carried out. The emperimental results showed that the two resonant wavelengths of the PMFBG were sensitive to temperature and axial strain, namely the cross sensitivities existed. The difference of two resonance wavelengths were very low sensitive to the temperature, unsensitive to the axial strain and very strong orientation-related sensitive to the transverse load.Finally, the influences of two types of contacting materials to the sensing characteristics of PMFBG were analyzed. Isinglass was chosen as the contacting material of the PMFBG weighing sensor. The sensor structure was primarily designed. One resonant wavelength and the wavelength difference were used by the sensor to measure the temperature and transverse load simultaneously. The transverse load measurement range of sensor was from 0 to 300kg with a high accuracy of 0.3kg, and the range of temperature measurement was from 25℃to 80℃with a accuracy of 1℃. The sensor had the advantsges of light weight, small volume, high sensitivity, good ability of anti-electromagnetic interference and insulation, and it was convenient for remote monitoring. It can be used in the field of weighing.