Sensitive Fiber Temperature Sensor Research Articles

Highly sensitive temperature sensor based on the reciprocal thermal responses of cascaded dual-cavities

A highly sensitive fiber temperature sensor based on cascaded multimode fiber cavity and polymer cavity between single mode fibers was proposed. A three-beam Fabry-Pérot interferometer was obtained. We demodulated the interference spectrum by means of the fast Fourier transform and the signal filtering. As the thermal response of the polymer cavity and the multimode fiber cavity are negative and positive, respectively, the high temperature sensitivity can be achieved by a subtraction between the two reciprocal thermal responses. Experimental results show that the sensitivity of the temperature sensor is as high as 2.95 nm/°C in the measurement range between −15 °C and 35 °C. The proposed sensor may find widespread application in biomedicine and environmental science due to its simple preparation method and high sensitivity.

Sensitivity-Enhanced Fiber Temperature Sensor Based on Vernier Effect and Dual In-Line Mach–Zehnder Interferometers

A highly sensitive fiber temperature sensor based on in-line Mach-Zehnder interferometers (MZIs) and Vernier effect was proposed and experimentally demonstrated. The MZI was fabricated by splicing a section of hollow core fiber between two pieces of multimode fiber. The temperature sensitivity obtained by extracting envelope dip shift of the superimposed spectrum reaches to 528.5 pm/°C in the range of 0 °C-100 °C, which is 17.5 times as high as that without enhanced by the Vernier effect. The experimental sensitivity amplification factor is close to the theoretical predication (18.3 times).The proposed sensitivity enhancement system employs parallel connecting to implement the Vernier effect, which possesses the advantages of easy fabrication and high flexibility.

Isopropanol-sealed multimode microfiber for temperature sensing

Abstract This paper presents a low-cost and high-sensitivity temperature sensor based on an isopropanol-sealed multimode microfiber (MMMF). Isopropanol is a kind of material with a high thermo-optic coefficient. Refractive index (RI) of isopropanol changes with the surrounding temperature variation allowing high-sensitivity temperature sensing. By inserting the MMMF into an isopropanol-sealed capillary, a simple and highly sensitive fiber temperature sensor is implemented. Theoretical and experimental results demonstrate that the tapered multimode fiber can efficiently excite high-order cladding modes, the MMMF can enhance the multimode interference and increase the interaction between the evanescent wave and the isopropanol. The characteristics of the measured transmission spectra under different conditions are evaluated. Experimental results demonstrate that the temperature sensitivity increases with the decreasing diameter of MMMF. The maximum temperature sensitivity of −4.12 nm/°C is obtained over the range of 30 °C–50 °C. This packaging technology not only offers a more stable structure but also improves the temperature sensitivity for the thermo-optic effect of isopropanol and the thermal expansion effect of packaging materials.

Compact optical fiber temperature sensor with high sensitivity based on liquid-filled silica capillary tube.

We propose a highly sensitive fiber temperature sensor based on a section of liquid-sealed silica capillary tube inserted in a single-multi-single-mode fiber structure. The liquid polymer is filled into the silica capillary tube through two micro-holes drilled by a femtosecond laser. Then the micro-holes are blocked by UV curable adhesive with ultra-small volume. Obvious Mach-Zehnder interference peaks were shown in its transmission spectrum. The proposed fiber temperature sensor can be reliably used for actual point detection owing to its high sensitivity (8.09nm/°C), good linearity (99.93%), compact size, good mechanical property, high fabrication efficiency, and good repeatability and stability.

Highly sensitive liquid-sealed multimode fiber interferometric temperature sensor

A highly sensitive optical fiber temperature sensor based on liquid-sealed coreless multimode fiber (also called no core fiber, NCF) interferometer is proposed and experimentally demonstrated. By inserting the interferometer into a liquid-sealed capillary, a simple and highly sensitive fiber temperature sensor can be implemented. Owing to the high thermo-optic coefficient of the liquid and thermal expansion of the sealant, the interferometric spectra of the proposed sensor are shifting obviously with the variation of temperature; temperature response of the sensor can be effectively modulated through this way. Experimental results show that the sensitivity of the temperature sensor can be improved by tuning the refractive index (RI) value of the sealed liquid; a maximum value of 5.15nm/°C has been obtained when the RI value of the sealed liquid is 1.450, it is close to the RI of the NCF.

Optical fiber temperature sensor using a gain-switched Fabry–Perot semiconductor laser self-seeded from a linearly chirped fiber Bragg grating

We present a highly sensitive fiber temperature sensor based on a gain-switched Fabry–Perot semiconductor laser self-seeded from a linearly chirped fiber Bragg grating. A temperature resolution of better than 0.1 °C was demonstrated. This sensor not only has the advantage of robustness against fluctuating light levels, but also obviates the need for fine wavelength discrimination.