Wei Fan

To develop compact and sensitive humidity sensors for environmental monitoring and industrial applications, a fiber-optic Fabry–Perot interferometric humidity sensor based on PVA-GQDs composite film is proposed. The device consists of two polished fiber ceramic ferrules assembled in a ceramic split sleeve, with a humidity-sensitive PVA or PVA-GQDs coating on one ferrule end face. Experimental results show that the PVA-GQDs sensor achieves sensitivities of −1.1174 and −1.8188nm/%RH in the humidity ranges of 32%–50% RH and 50%–60% RH, respectively, which are higher than those of the pure PVA sensor. Moreover, it reduces temperature cross-sensitivity by 91.5% and exhibits a minimum standard error of 0.01655% RH. The proposed sensor provides a simple fabrication method, a compact structure, and a stable humidity response.

Polarizers are key devices for polarization management in photonic integrated circuits. We propose a broadband, on-chip transverse electric (TE)-pass polarizer designed using an inverse design based on a bent silicon hybrid plasmonic grating (HPG). The device integrates five hybrid plasmonic waveguides with different optimized bending angles and a single-mode silicon waveguide. This unique HPG structure effectively suppresses the transmission of transverse magnetic polarization modes while achieving low-loss propagation of the TE mode due to plasmonic control over the effective index and mode distribution. Numerical results show that the polarizer achieves a polarization extinction ratio (PER) of 34.36 dB and an excess loss (EL) of 0.5 dB at the wavelength of 1550 nm. Furthermore, the TE-pass polarizer maintains EL20 dB over 300 nm bandwidth, covering the E-, S-, C-, and L-bands within a compact footprint of 5.03×5.1 μm2. The inverse-designed structure exhibits fabrication tolerance and is fully compatible with standard silicon-on-insulator manufacturing processes.

In order to meet the needs of accelerometers in vibration monitoring, a fiber Bragg grating (FBG) accelerometer based on a miniature slide rail is proposed. The accelerometer consists of two FBGs, a miniature slide rail, two spring plungers, and a mass block. Since the motion of the two fiber gratings is in opposite directions, the induced displacement of the center wavelength can wipe one another out. So, the effect of temperature can be reduced and the sensitivity of the fiber grating can be improved. Through theoretical analysis and experimental verification, the resonant frequency, sensitivity, and lateral immunity of the sensor are studied. The experimental results show that the effect of temperature on the sensor structure is reduced to 0.3 pm/°C in the range of 22.5 °C–90 °C. The resonant frequency of the accelerometer is 200 Hz, and the FBG accelerometer has a broad frequency range from 0.5 to 150 Hz, with a corresponding sensitivity range from 307.3 to 319.2 pm/g, and the lateral immunity is less than 0.5%. The sensor is simple in structure and easy to manufacture. Therefore, it has great prospects for application in structural health monitoring and other fields.

In view of the complexity of gait recognition and the unsatisfactory recognition effect in different states, a new method of gait recognition based on dynamic and static features fusion is proposed. In order to retain as many gait characteristics as possible, the gait energy graph is chosen as the static feature, stride and step frequency as dynamic features, and feature fusion is carried out. A method of kernel principal component analysis combined with local preserving projection to reduce dimension of gait feature (KPCA-LPP) is proposed. Aiming at the problem of low recognition rate in non-regular perspective and multiple-view recognition, the paper improves the multi-view gait network, and uses the fast decomposition orthogonal matching tracking algorithm based on kernel function to classify and identify. The simulation results show that the proposed algorithm has some advantages over the existing classical algorithms, good recognition rate, the recognition effect is not affected by the interference factors such as backpack and overcoat, and the robustness is better.