A time- and wavelength-division multiplexing sensor network based on ultra-weak fiber Bragg gratings (FBGs) was proposed. The low insertion loss and the high multiplexing capability of the proposed sensor network were investigated through both theoretical analysis and experimental study. The demodulation system, which consists of two semiconductor optical amplifiers and one high-speed charge-coupled device module, was constructed to interrogate 2000 serial ultra-weak FBGs with peak reflectivity ranging from −47 dB to −51 dB and a spatial resolution of 2 m along an optical fiber. The distinct advantages of the proposed sensor network make it an excellent candidate for the large-scale sensing network.

This paper presents a high-resolution, signal-jump-free demodulation method for Fiber Bragg Grating (FBG) systems employing a low-cost spectrometer. Utilizing a modified Logarithm Gaussian Levenberg-Marquardt (LGLM) method, the proposed approach enables precise and stable Bragg wavelength tracking. The principles of the LGLM method were thoroughly analyzed and derived, affirming the feasibility and robustness of the FBG system. Static experiments with 9 sampling points demonstrated that the LGLM method achieves a standard deviation (STD) of 1.7 pm, representing a 6.9-fold improvement over conventional Gaussian fitting. Strain experiments confirmed a strong linear relationship between strain and Bragg wavelength, with dynamic strain measurements at a 6 kHz sampling rate showing that the LGLM method effectively eliminates signal jumps observed in Gaussian fitting. At 500 Hz, the minimum detectable strain (MDS) of the LGLM method was determined to be 0.0173 με/Hz^−1/2, more than 10 times better than Gaussian fitting. Temperature experiments conducted over a range of 100–700 °C further validated the method's performance, with the LGLM achieving an STD of 1.56 pm and a variation of 3.4 pm, representing improvements of 10.25 times and 52.9 times, respectively, compared to Gaussian fitting. These findings demonstrate the exceptional sensitivity, stability, and robustness of the LGLM method for demanding applications such as high-temperature monitoring and structural health diagnostics.

A field-programmable gate array (FPGA)-based large-capacity sensing network with ultra-weak fiber Bragg gratings (FBGs) is proposed and experimentally studied. The demodulation system is constructed to interrogate 1642 serial time-division-multiplexing FBGs with a peak reflectivity of about ?40 dB and equal separations of 2.5 m. Two semiconductor optical amplifiers and an InGaAs linear sensor array controlled by an FPGA are introduced to the demodulation system to achieve fast, precise, and flexible interrogation. The low crosstalk and spectral distortion are investigated through both theoretical analysis and experiments.

The cantilever-beam accelerometer based on dual-fiber-Bragg gratings (FBGs) is proposed to detect the geosound caused by debris flow. The structure and working principle of the accelerometer are demonstrated. Dual FBGs are introduced to improve the sensitivity and frequency response of the accelerometer. By using a bend insensitive optical fiber and ultrathin coating, the sensitivity and serial multiplexing performance of the sensor are improved remarkably. Experimental results show that the accelerometer, with a sensitivity of $900pm/g$ and the natural frequency of 280 Hz, can effectively detect the geosound caused by debris flow.

Pressure sensitivity and gas desorption time are two key parameters that determine the performance of pressure sensors. Polydimethylsiloxane (PDMS) film shows potential in highly sensitive pressure sensor, however the trade-off between high sensitivity and low desorption time presents a challenge. This article proposes a novel gas pressure sensor with ultra-high sensitivity and ultra-fast desorption based on a tapered fiber coated with Polydimethylsiloxane/Metal Organic Framework (PDMS/MOF) composite film. By doping a specific MOF with amino groups into PDMS, the gas adsorption capacity can be greatly enhanced. More importantly, the gas desorption time can be greatly reduced because the large pores in MOF create fast transport channels in PDMS. Experimental results show that the gas pressure sensitivity increases with an increase of MOF doping amount, leading to shorter gas desorption times. The sensor achieves a gas pressure sensitivity of up to −228.32 nm/MPa and a gas desorption time as short as 16 s within the pressure range of 0–100 KPa with doping amount of 5 wt%. A fiber Bragg grating is connected in series for compensation of temperature crosstalk. The proposed sensor provides a good reference for integrating porous materials and optical fibers in high-sensitivity gas and biochemical sensing applications.