Hybrid long period fiber grating for measuring refractive index and pressure in downhole application

A hybrid long period fiber grating (HLPFG) sensor was utilized for sensing the refractive index and pressure for downhole applications. The HLPFG is fabricated by fattening and tapering on a single mode fiber, utilizing a standard fusion splicing and a CO2 laser, respectively. The limit of detection (LOD) of the HLPFG for the RI measurement in the range from 1.3150 to 1.3559 is 4×10^-5 as a refractometer sensor which can be used for analysis of multicomponent in native petroleum. Pressure sensitivity of the HLPFG sensors in the range from 500 to 6000 psi is -0.6 pm/psi. With a 10 pm resolution for the wavelength shift detection our OSA, the LOD of the device at room temperature for pressure measurement is calculated to be 17 psi. This sensor can be used as a high pressure sensor in downhole application.