Since high efficiency and zero-carbon emission, hydrogen, as a clean energy carrier, is potentially an alternative fuel. Unfortunately, hydrogen is a gas with a high diffusion coefficient, wide explosion limit, and low ignition energy. Thus, to ensure the safe use of hydrogen, accurate and rapid monitoring of hydrogen leakage and abnormal concentration change must be addressed immediately, which is a critical scientific and technical problem. Therefore, we propose an optics-mechanics coupling fiber hydrogen sensor without electricity-related hazard factors. This proposed fiber hydrogen sensor is constructed by combining optics-mechanics coupling, specific adsorption of hydrogen to the surface of palladium (Pd), and Fabry-Pérot (F-P) interference mechanism; the optics-mechanics coupling is aroused by hydrogen-induced stress in the suspended Pd film, which functions as an F-P resonator mirror and a hydrogen-sensitive material. According to this configuration and principle, we achieve efficient and high-selective hydrogen detection at room temperature. This optics-mechanics coupling-based fiber hydrogen sensor is characterized by the high sensitivity (0.397 nm/1%), extensive dynamic range (0.5%–3.5%), 8 s response time, and 16 s recovery time. Hence, as an intrinsically safe hydrogen sensor with the high sensitivity and quick response, this optics-mechanics coupling-based fiber hydrogen sensor can be widely used in the hydrogen energy industry chain for rapid and high-performance hydrogen detection.

We propose a high-sensitivity optical fiber relative humidity (RH) sensor based on multiwalled carbon nanotubes (MWCNTs)/graphene oxide (GO) composite, which functions as the humidity-sensitive film. The optical component of this demonstrated sensor is a single-mode fiber-solid core fiber-single-mode fiber-based multimode interference structure. For the composite sensitive film, GO is used as a dispersant for two types of MWCNTs with different lengths. Subsequently, GO-dispersed MWCNT hybrid films are formed on fiber surfaces by the dip-coating method. Herein, the hydroxylated MWCNTs can function as supporting structures to avoid the formation of layer-by-layer stacked GO, and this destacking humidity-sensitive film is beneficial to enhance water molecules' absorptive capacity. To clarify the principle, the interaction between composite humidity-sensitive film and water molecules is investigated. The experimental results reveal that the interference fringe shows a redshift with the increase in RH. When RH changing from 40% to 90%, the sensor probe with long-range MWCNT-based film has higher sensitivity than that with short-range MWCNT-based film, which demonstrates the effect of the supporting action of MWCNTs. Besides, a larger specific surface area and pore size of long-range GO-MWCNTs benefit sensitivity enhancement. In addition, this proposed sensor has good repeatability, stability, and a large linear measurement range (40% RH-90% RH).

Since photo-induced polymerization of the ultra-violet (UV)-curing adhesive from a fluid state to a solid state is an exothermic process, the UV curing exothermic behavior can be regarded as a potential evaluation methodology to analyze UV-curing kinetics. Herein, a fiber Bragg grating (FBG)-based UV curing exothermic behavior monitoring is proposed to evaluate the UV-curing dynamic process and analyze a series of thermal and mechanical properties changes during curing. The exothermic behavior of the UV curing adhesive during curing and the feasibility of FBG-based curing kinetic analysis scheme are verified experimentally, full cycle cure monitoring of the UV curing adhesive can be realized by this FBG-based curing kinetic analysis scheme, and the UV-curing kinetics of four different types of the UV curing adhesive are corresponding to different exothermic behaviors. Compared with curing process evaluation based on refractive index variation, this FBG-based exothermic behavior monitoring has the ability to extract more details of the curing process, and some curing stages with negligible refractive index changes also can be distinguished. By using this proposed scheme, the UV-curing dynamic process and multiple characteristic parameters, such as curing time, time constant, transient temperature rise, and residual stress, can be evaluated, which may contribute to evaluating and analyzing UV-curing kinetics more comprehensively.

Herein, a luminescent fiber device for detecting ultraviolet (UV) intensity, which comprises a UV probe and a photoelectric converter, is proposed. The UV probe consists of a glass tube filled with luminescent material, which can be used for the efficient radiation conversion of UV radiation to the visible spectral region. The luminescent material, Y2O2S:Eu3+, is mixed with polydimethylsiloxane (PDMS) to form the core of the UV probe. Subsequently, the UV radiation response of the luminescent fiber device is investigated; the experimental results demonstrate that the direction-independent UV detection can be realized by using this luminescent fiber UV detection device while UV light is radiated radially along the UV probe. In addition, since partial discharge (PD) is accompanied by UV radiation, we hope to develop a spectral PD detection scheme based on optical fiber technology, which can broaden the role of optical technology and optical fiber technology in the field of PD detection.

The reason the prism-based SPR scheme can be regarded as a commercial solution is that it has some advantages, such as good stability, high-sensitivity, and so on. However, due to the special optical propagation property of the traditional commonly used triangular prism, there is a seemingly random and inaccurate surface plasmon excitation angle that is unfavorable to regulate the light path and limit SPR miniaturization. Thus, a prism-coupled SPR system is developed by using a special trapezoidal prism function as a coupling element. The trapezoidal prism can contribute to a significant simplification in adjustment/assembling and minification in optical configuration. Experimental results demonstrate that the system exhibits good resonance depth, achieves a refractive index sensitivity of 3465 nm/RIU, and maintains high stability with a relative standard deviation of 0.1020%. Additionally, the potential of this SPR system for biochemical sensing has been verified by the kinetics of immunoglobulin G binding. Hence, the system features a structurally simple design, ease of adjustment/assembly, stable performance, and compact configuration, which may provide valuable insights for designing and developing new practical SPR systems.