We propose a dual-channel surface plasmon resonance (SPR) sensor based on hollow-core fiber (HCF) for the simultaneous measurement of the liquid refractive index (RI) and ambient temperature. The simultaneous monitoring of two parameters can effectively realize the temperature compensation of liquid RI measurement. One channel is coated with a silver film to sense the liquid RI, the other channel is coated with a gold film and polydimethylsiloxane (PDMS) to sense the ambient temperature, and the cross sensitivity of the multi-parameter measurement is solved using the dual-wavelength matrix method. The sensing performance of the proposed sensor is investigated both theoretically and experimentally, which proves that it can achieve high sensitivity in a relatively wide measurement range. The experiment shows that the liquid RI sensitivity is as high as 2400.079 nm/RIU in the RI range of 1.3333–1.3770, and the temperature sensitivity is −1.29 nm/°C in the temperature range of 40 °C–90 °C. This work provides a new scheme for the multi-parameter measurement, and the proposed sensor has the advantages of simple and compact structure, low cost, wide measurement range and high sensitivity, which promises broad application prospects in the simultaneous monitoring of liquid RI and temperature.

In this work, a new method was explored for developing temperature and relative humidity (RH) optical fiber sensors based on surface plasmon resonance (SPR). A SPR optical fiber sensor coated with carboxymethyl cellulose (CMC) and polydimethylsiloxane (PDMS) was proposed for the simultaneous measurement of RH and temperature. The sensor was fabricated by connecting two no-core optical fibers (NCFs) using multimode optical fibers (MMFs). Metal films were deposited on the surface of NCFs and further coated with CMC and PDMS. CMC coating was used for RH sensing based on the change of refractive index (RI) caused by water absorption; PDMS coating was used for temperature sensing based on its RI change with temperature. Univariate analysis showed that there was very weak interaction between RH and temperature measurement. For RH sensing, the sensitivities were −1.230 nm/RH%, −2.932 nm/RH% and −0.431 nm/RH% when RH were 50%~65%, 65%~70% and 70%~80%, respectively; for temperature sensing, the sensitivity was −2.213 nm/°C at 10 °C~50 °C. The proposed sensor can not only respond to both temperature and RH variation, but also compensate the cross sensitivity between the two parameters. It is simple in structure, easy to manufacture and efficient in the simultaneous detection of temperature and RH, which promises great application prospects in the fields of agriculture, food industry, biological field and other production activities.

Multi parameter measurement and device miniaturization are the development trend of optical fiber sensors. Here we propose a compact dual channel surface plasmon resonance (SPR) fiber sensor which can measure the liquid refractive index (RI) and ambient temperature in real time. This sensor coats metal and polydimethylsiloxane (PDMS) on the side of a no-core D-shaped fiber: the channel for measuring the liquid RI is covered by silver film, and the channel for temperature sensing is covered by gold film and PDMS. The sensing sensitivity is analyzed by finite element method. When the liquid RI is within 1.33~1.44 and the temperature is within 0~180 °C, the corresponding maximum spectral sensitivity is 12530 nm/RIU and -3.465 nm/°C, respectively. The sensor has wide detection range, compact structure and temperature compensation function, which is suitable for environmental monitoring and high-precision sensing.

Novel fiber Bragg grating (FBG) relative humidity (RH) sensors based on polyimide (PI) doped with graphene quantum dots (GQDs) are proposed and experimentally demonstrated. The effects of GQDs doping on the sensor performance were investigated. The sensitivity of the humidity sensor could be increased by 96.36% when the doping mass fraction of GQDs was optimized at 0.2%. The FBG humidity sensor based on PI-doped GQDs exhibited good linearity at different operating temperatures in the RH range of 10–90%. Moreover, the excellent linearity of the temperature sensitivity facilitates the temperature compensation of these sensors. GQDs-doped PI is an excellent moisture-sensitive material that significantly improves the sensitivity of FBG humidity sensors, making it a promising candidate for humidity sensing in various applications.

In this article, a surface plasmon resonance (SPR) sensor was designed based on the no-core optical fiber (NCF) for the simultaneous measurement of magnetic field intensity and ambient temperature. The sensor structure was mainly comprised of two NCF segments spliced between two multimode optical fibers, and different metal films were deposited on the NCF surface to generate the SPR effect: the NCF coated by silver and wrapped by MF was used for magnetic field sensing and the NCF coated by gold and wrapped by PDMS was used for temperature sensing. The proposed sensor successfully avoided the influence of temperature on magnetic field sensing, and vice verse. Detailed experimental investigation showed that in the magnetic field intensity range of 0–248 Gs, a maximum sensitivity of 132 pm/Gs was obtained with good linearity (coefficient of determination 0.991), and in the temperature range of 20 °C–60 °C, the corresponding sensitivity was −1.960 nm/°C with a linearity higher than 0.997. The proposed sensor can perform an accurate sensing even in weak magnetic field environment and simultaneously provide information about temperature variation. Being simple in structure, easy to manufacture and stable in performance, this sensor provides a feasible solution for the integration and miniaturization of multi-parameter measurement.

It is a challenging and valuable work to design and manufacture temperature compensated all-fiber ultraviolet (UV) sensor. In this paper, we creatively use a simple and compact optical fiber sensor based on surface plasmon resonance (SPR) for simultaneous detection of UV and ambient temperature. Different coatings (Ag/polydimethylsiloxane (PDMS) and Ag/ZnO/PDMS) are used to split a length of no-core optical fiber (NCF) into two sensing regions, which generates a transmission spectrum with two distinct SPR dips. The proposed sensor achieves a temperature sensitivity of -2.542 nm/°C in the 15-35 °C range and an UV sensitivity of -0.605 nm/(mW/cm ² ) in the range of 0-17.20 mW/cm ² . The matrix established by the wavelength shift of two dips can demodulate UV and temperature changes, and provide temperature compensation for UV detection. Additionally, even in surroundings of complex and changeable UV intensity and ambient temperature, the sensor shows excellent stability and repeatability, as well as great potential in UV sensing, providing a reference for the development of multi-parameter optical fiber sensors.