A high resolution and large range fiber Bragg grating temperature sensor with vortex beams

Abstract

The vortex beam owns helical phase factor, orbital angular momentum, and hollow structure of intensity distribution. It is widely applied in information coding, optical manipulation and optical sensing. This paper attempts to design a fiber Bragg temperature sensor based on vortex light, including an orbital angular momentum (OAM) beam transmitted by fiber Bragg grating (FBG), an optical fiber path used to eliminate errors, and a Gaussian beam, which is used to interfere with FBG transmission light. The interference pattern of a Gaussian beam and an OAM beam rotates with the changes of phase difference between the two beams. When the temperature changes, FBG is affected by the thermal optical effect and thermal expansion effect, and the central wavelength of the reflected spectrum will shift. Based on the relationship between wavelength shift and temperature change, temperature measurement in a large range can be realized. Additionally, the Filter is placed behind the FBG, and the transmission light (λ=1.466μm) with less reflection is selected to interfere with the Gaussian light, with the change of phase of transmission light, the rotation of the interference pattern will change accordingly. The temperature change corresponding to the 2π rotation of the interference pattern can be obtained, thus temperature measurement with high resolution can be realized. The simulation results show that when the temperature range is 27 °C–427 °C, the sensitivity of this sensor is 14.42 pm/°C. On the basis of the rotation of the interference pattern, when the rotation angle of the temperature-induced interference pattern change within 2π the temperature sensitivity is 1.529 rad/°C, based on the angular resolution of CCD, the theoretical resolution of temperature measurement is 6.3e−7 °C. Similar to the cursor effect, the main ruler measures a wide range of temperature changes according to wavelength drift, and the cursor is a high-resolution measurement of temperature according to the rotation angle of the interference pattern.