Glucose sensitive membrane (GSM) consists of glucose oxidases (GODs) and matrix material (for example, polyacrylamide gel). In this paper, we have investigated the optical property and adsorption isotherms of a GSM based on a terminal reflection optical fiber SPR sensor. Firstly, we reported the fabrication of one kind of GSM which was made of immobilized GODs on SiO₂ nanoparticles and PAM gel. Then, we investigated the effects of GSM thickness, GOD content, solution pH and ambient temperature on the reflected spectrum of sensor, and the optimum parameters of the sensor, such as, GSM thickness of 12 times pulling, 4 mg/mL of GOD content in GSM, 7.0 of solution pH and 40 °C of measuring temperature were obtained. Thirdly, we measured the wavelength shifts of the optimized SPR sensor in the solutions with different glucose concentrations. As the glucose concentration increases from 0 to 80 mg/dL, the resonance wavelength decreases approximately linearly and the corresponding sensitivity is about 0.14 nm/(mg/dL). Finally, we investigated the RI of the GSM, the concentration of glucose into GSM and the adsorption isotherm of GSM by the combination of SPR experiment data, theoretical simulation and Gladstone-Dale mixing rule. As the glucose concentration is in the region of [0, 80] mg/dL, the adsorption of GSM for glucose can be explained by the Freundlich isotherm model. As the glucose concentration is in the region of [120, 500] mg/dL, the Langmuir isotherm model is more suitable to describe the adsorption process of GSM for glucose.

For the online writing of ultra-weak fiber Bragg gratings (FBGs) in the drawing optical fibers, the effects of the intensity profile, pulse fluctuation and pulse width of the excimer laser, as well as the transverse and longitudinal vibrations of the optical fiber have been investigated. Firstly, using Lorentz-Loren equation, Gladstone-Dale mixing rule and continuity equation, we have derived the refractive index (RI) fluctuation along the optical fiber and the RI distribution in the FBG, they are linear with the gradient of longitudinal vibration velocity. Then, we have prepared huge amounts of ultra-weak FBGs in the non-moving optical fiber and obtained their reflection spectra, the measured reflection spectra shows that the intensity profile and pulse fluctuation of the excimer laser, as well as the transverse vibration of the optical fiber are little responsible for the inconsistency of ultra-weak FBGs. Finally, the effect of the longitudinal vibration of the optical fiber on the inconsistency of ultra-weak FBGs has been discussed, and the vibration equations of the drawing optical fiber are given in the appendix.

A novel fiber optic refractive index (RI) and temperature sensor based on a multimode-singlemode-multimode fiber (MMF-SMF-MMF) structure coated with graphene-metal hybrid films was proposed and investigated. The SPR-based RI sensitivity is improved by the addition of the graphene layer above or below the gold coating of the fiber, and then further enhanced with the addition of gold-silver core-shell nanoparticles (Au@Ag NPs). Furthermore, the surface of graphene-Au-Au@Ag NPs film was modified with polydimethylsiloxane (PDMS) for temperature sensing, achieving a high sensitivity of -1.02 nm/°C with good repeatability. This new structure with graphene-gold-Au@Ag NPs-PDMS hybrid films shows applications in many fields including environmental protection, clean energy and nano-medicine.

Based on fiber Bragg grating (FBG), an online monitoring system for the etching process of optical fiber in a hydrofluoric (HF) acid solution has been designed. The variation curves of the wavelength shifts of FBGs with etching time at three different temperatures have been obtained and analyzed theoretically. The results show that the etching process of optical fiber in HF acid solution can be understood by the variation of the wavelength shift of FBG with etching time. Finally, required tapered fiber tips can be made by controlling the etching velocity and the pulling velocity of optical fiber from the etching solution.

An improved glucose sensitive membrane (GSM) is prepared by immobilizing glucose oxidase (GOD) onto a mixture of silica mesocellular foams (SiMCFs) and SiO₂ nanoparticles (SiNPs) and then trapping it in a polyvinyl alcohol (PVA) gel. The membrane is coated onto a gold-glass sheet to create a surface plasmon resonance (SPR) sensor. A series of experiments are conducted to determine the optimized parameters of the proposed GSM. For a GSM with a component ratio of SiMCFs: SiNPs = 7: 3 (mass rate), the resonance angle of the sensor decreases from 68.57° to 63.36°, and the average sensitivity is 0.026°/(mg/dL) in a glucose concentration range of 0 mg/dL‒200 mg/dL. For a GSM with a component ratio of SiMCFs: SiNPs = 5: 5 (mass rate), the resonance angle of the sensor decreases from 67.93° to 63.50°, and the sensitivity is 0.028°/(mg/dL) in a glucose concentration range of 0 mg/dL‒160 mg/dL. These data suggest that the sensor proposed in this study is more sensitive and has a broader measurement range compared with those reported in the literature to date.

In this work, we have proposed a novel long-range surface plasmon resonance (LRSPR) sensor with sharp reflection spectrum, which consists of a glass prism, a (A/B)⁴-type waveguide-coupled layer and a metal layer. To reveal its sharp reflection spectrum perfectly, we have simulated the effects of all factors of this LRSPR sensor on the reflection spectrum, and finally presented the optimal parameters of the LRSPR sensor with sharp reflection spectrum.