The optical Vernier effect is a powerful tool for improving the sensitivity of an optical sensor, which relies on the use of two sensor units with slightly detuned frequencies. However, an improper amount of detuning can easily cause the Vernier effect to be unusable. In this work, the effective generation range of the Vernier effect and the corresponding interferometer configuration are suggested and experimentally demonstrated through a tunable cascaded Fabry–Perot interferometer structure. We further demonstrate a practical method to increase the magnification factor of the Vernier effect based on the device bandwidth. Only the optical path length of an interferometer probe and the sensitivity of the measurement parameters are needed to design this practical interferometer based on the Vernier effect. Our results provide potential insights for the sensing applications of the Vernier effect.

A compact and robust Fabry-Perot interferometer (FPI) based on polymer core is proposed and experimentally demonstrated. The fabrication is low-cost and has simple processes, including fusion splicing and polymer injection. Its characteristic is that the polymer fills the entire capillary core, which is easy to demodulate, and provides a good platform for the refractive index measurement of the polymer after curing. The experimental result shows a linear temperature sensitivity of 1226.64 pm/°C between 39°C and 54°C. Furthermore, we also used the Vernier effect to improve the temperature sensitivity as high as −15.617 nm/°C. The proposed FPI structure provides potential application in the research of sensors and polymer optical fibers.

This paper proposes a Fabry–Perot pressure sensor based on AB epoxy adhesive with ultra-high sensitivity under low pressure. Fabry–Perot interference, located between single-mode fiber (SMF) and hollow-core fiber (HCF), is an ultra-thin AB epoxy film formed by capillary action. Then the thick HCF was used to fix the HCF and SMF at both ends with AB epoxy adhesive. Experimental results show that when the thickness of AB epoxy film is 8.74 μm, and the cavity length is 30 μm, the sensor has the highest sensitivity. The sensitivity is 257.79 nm/MPa within the pressure range of 0–70 kPa. It also investigated the influence of the curing time of AB epoxy on the interference spectrum. Experiments showed that the interference spectrum peak is blue-shifted with the increase of curing time. Our study also demonstrated the humidity stability of this pressure sensor. These characteristics mean that our sensor has potential applications in the biomedical field and ocean exploration.

Due to the development of power devices, the preparation of high reliability Cu joints using high-performance lead-free solder is an effective way to address issues. In this paper, different porosity Cu-Ni foam reinforced Sn composite solder were successfully prepared. The results shown that the alloying treatment significantly improved the tensile strength of composite solder. The solid-phase transformation of (Cu,Ni) 6 Sn 5 to (Ni,Cu) 3 Sn 4 occurs in joint with the decrease of Cu-Ni foam porosity, and the growth of Cu 3 Sn layer was inhibited, thus achieving the refinement of the intermetallic compound in the joint. The mutual encouragement of phase change and grain structure led to the fast transformation of (Cu,Ni) 6 Sn 5 to (Ni,Cu) 3 Sn 4 . As the porosity of the Cu-Ni foam decreased, the Cu joint's strength steadily rose. And the soldering time was prolonged, the joint’s shear strength initially rose and subsequently fell. The shear strength of the Cu joint employing composite solder reinforced by Cu-Ni foam with a 60 percent porosity bonded for 60 minutes, reaching a maximum value of 79.9Mpa.

In a system with the 3-way regulating valve, low energy consumption high efficiency based on fluid dynamics CFD software, for the 3-way regulating valve of the 3 d simulation for internal flow property research, obtained the pressure within the valve flow turbulence kinetic energy and turbulence dissipation rate etc. The results show that the flow field information with the increase of the opening, the seat area on the turbulence kinetic energy and turbulence dissipation rate increases sharply, change law instead of the seat position. The existence of transition cone can greatly reduce the turbulent kinetic energy and the turbulent dissipation rate of the upper seat in the wide opening range and the valve in the small opening range. Long-term avoidance of the valve working in the minimum-opening condition will be beneficial to the protection of the valve.