Fiber Bragg Grating Temperature Sensor by the Wavelength Tuning Using the Temperature Dependence of VCSEL

In this paper, a low-cost optical temperature sensor is implemented, using a fiber Bragg grating (FBG) as the temperature probe and a low-cost VCSEL with temperature-dependent output wavelength as the light source. To analyze the wavelength of the reflected light from the FBG, an interrogation was applied using a method of referring to the internal temperature according to the output wavelength of the VCSEL. When the temperature of the VCSEL was adjusted from 14 to 52.2°C, the output wavelength varied from 1519.90 to 1524.25 nm. The degree of wavelength tuning according to temperature was 0.114 nm/°C. The variable wavelength repeatability error according to temperature was ±0.003 nm, and the temperature measurement error was ±0.18°C. As a result of measuring the temperatures from 22.3 to 194.2°C, the value of the internal temperature change of the light source according to the applied temperature ΔΤ was 0.146°C/ ΔΤ , the change in reflected wavelength of the temperature probe according to applied temperature ΔΤ was measured at 16.64 pm/°C. and the temperature measurement error of the sensor was ±1°C.