Study On The Fabrication Of Fiber Bragg Gratings And Application In Pressure Sensor

Fiber Bragg grating (FBG) is a new type passive optical component with the refractive index modulated along the fiber length. Recently FBG has become a very important component for optical sensing devices considering its many merits such as high sensitivity, light weight, small size, easily array and wavelength encoded, and it has become one of the most promising optical device. However, because of the low pressure sensitivity of bare FBG and its sensitive simultaneity of both temperature and strain, bare FBG cannot be directly used in sensing area, and the application in harsh environments (high temperature and high pressure) with high resolution and sensitivity remains a big challenge.FBG was fabricated on hydrogen loaded single mode optical fiber. The optimal fabrication parameters were concluded by considering the affect of the laser power, frequency and exposure time.Based on full analysis of bare FBG characteristics, a thin-wall cylinder pressure sensor has been designed and fabricated, which can be used in the measurement of high temperature and high pressure environment. By using ANSYS software, the strain characteristics of the cylinder (made of four different kinds of material and in different sizes) were calculated. The most theoretical result of pressure for stainless steel material 1Cr₁₈Ni₉ is 63MPa. The measurement ranges of actual pressure and temperature are 0～42MPa and 20℃～230℃, respectively. Meanwhile, because of the reference FBG, cross-sensitivity of pressure and temperature is solved effectively.In order to achieve the most effective integration between FBG and sensor devices, and the steady result in high-temperature environment measurement, metal-coated FBG (MFBG) is has been used in pressure sensor, which brought a better result.