굽힘과 온도를 동시 측정하기 위해 CO2 Laser를 이용해 새긴 편광 유지 장 주기 광섬유 격자 센서에 관한 연구

Abstract

Many optical sensors have been proposed due to advantage of optical fiber such as small size, light weight, independence of electromagnetic interference, and corrosion resistance. Optical sensors can be used to measure variation of curvature, which is an important variable in the mechanical manufacturing industry and large-scale construction industries. To do this, sensors are constructed using various types of optical fibers. Accordingly, we constructed sensor system that can measure bending and temperature simultaneously using a polarization-maintaining long period fiber grating (PM-LPG) as a sensor head with a long-period fiber grating (LPG) inscribed on polarization maintaining fiber (PMF). The PM-LPG is written using a CO2 laser with ~10.6 μm, and has a grating period of ~505 μm and a total length of PM-LPG of ~14.65 mm. When bending is applied to the fabricated PM-LPG, compressive stress is applied to the LPFG and the dip of the resonant wavelength shifts. Likewise, when the changed temperature is applied to the PM-LPG, the dip of the resonant wavelength shifts due to the thermal expansion of the optical fiber. In this system, the input polarization is adjustable using the polarization controller included the sensor system, and it is possible to simultaneously measure bending and temperature using the two dips of resonant wavelengths that input polarizations are perpendicular to each other and that have the largest ER. As a result, the bending sensitivity obtained at the two polarized light state is ~22.232 nm/m-1 and ~33.378 nm/m-1, also, the temperature sensitivity is ~131.7 pm/℃ and ~39 pm/℃. Furthermore, the R2 values ​​obtained at the two polarized light state for bending and temperature are ~0.9916, ~0.981 and ~0.9929, ~0.998, respectively.