In this paper, an optical fiber composite Fabry-Perot interferometric (CFPI) sensor capable of simultaneous measurement of high temperature and strain is presented. The CFPI sensor consists of a silica-cavity intrinsic Fabry-Perot interferometer (IFPI) cascading an air-cavity extrinsic Fabry-Perot interferometer (EFPI). The IFPI is constructed at the end of the transmission single-mode fiber (SMF) by splicing a short piece of photonic crystal fiber (PCF) to SMF and then the IFPI is inserted into a quartz capillary with a reflective surface to form a single-ended sliding EFPI. In such a configuration, the IFPI is only sensitive to temperature and the EFPI is sensitive to strain, which allows the achieving of temperature-compensated strain measurement. The experimental results show that the proposed sensor has good high-temperature resistance up to 1000 °C. Strain measurement under high temperatures is demonstrated for high-temperature suitability and stable strain response. Featuring intrinsic safety, compact structure and small size, the proposed CFPI sensor may find important applications in the high-temperature harsh environment.

In order to overcome the shortcomings of the poor shear resistance of the bare optical fiber whose coating layer falls off due to harsh conditions, such as on aero-engines and the marine environment, the coaxial powder feeding laser cladding method (CPFLCM) is proposed to connect the optical fiber sensor and the substrate. The concentration field model of the powder flow is established in sections, the effective number model of particles and the corresponding laser attenuation rate are obtained. Through simulation, the influence of relevant parameters of laser cladding on the temperature field was analyzed, and the accurate parameters of laser cladding were optimized. Finally, the temperature rise trajectory of the substrate temperature field was verified by using the fiber grating temperature sensor. Through experiments, the quality of the molten pool and the optical transmission loss of the optical fiber sensor were analyzed, and the consistency of the simulation optimization parameters was verified. Through this paper, it can be concluded that the proposed CPFLCM can realize the effective connection of the optical fiber sensor to the substrate. It is of great significance in the application of optical fiber sensors in harsh environments of oceans and aerospace.

Ethylenediamine-functionalized cellulose was prepared by the reaction of chlorinated cellulose and ethylenediamine. Next, the ethylenediamine-functionalized cellulose supported with copper(II) was prepared by the reaction of ethylenediamine-functionalized cellulose and CuCl₂. The powdered product was mixed with a 1,2-dichloroethane solution of chlorinated polyvinyl chloride, and then cast into a film and decoppered. Finally, a copper(II)-selective extraction disc was obtained. Using the copper(II)-selective extraction disc for the spectrophotometric determination of Cu²⁺ in solution, the linear range for Cu²⁺ analysis was 40–1100 μmol L⁻¹, and the detection limit was 38 μmol L⁻¹ Cu²⁺. In the repeatability test for the analysis of 250 μmol L⁻¹ CuCl₂ solution using the copper(II)-selective extraction disc, the relative standard deviation of seven determinations was less than 4.3%. The levels of Cu²⁺ in porcine liver and wastewater were determined using this method. The determination results had no significant difference as compared with those by atomic absorption spectroscopy. However, the new method is more economical.

In light of the low resolution of the interference spectrum and the low demodulation accuracy of the existing interference-type refractive index sensors, a reflective mode interferometric sensor based on a Single-arm fiber-optic tapered probe (SAFTP) is proposed. This structure consists of a section of single-mode and no cladding fiber that is fused without eccentricity. By defining the depth-to-width ratio and preparing probes with different taper angles, the interference peaks are tuned to meet the high sampling resolution requirements of spectral measurement instruments. Within a limited bandwidth range, the greater the depth-to-width ratio, the wider the range of the measured physical quantity. From the perspective of spectral measurement instruments spectral acquisition, under the same bandwidth and number of acquisition points, the smaller depth-to-width ratio results in a higher spectral interference sampling resolution. Finally, the refractive index sensitivity of the SAFTP was calibrated under the optimal taper angle, allowing for the successful detection of the refractive index of silicone oil. Given the significant role of methyl silicone oil in aviation and precision instruments, it is crucial to utilize tunable SAFTP to measure the refractive index of silicone oil under various operating conditions. This will enable oil detection and assessment of silicone oil.