Fiber optic distributed acoustic sensing (DAS) technology is widely used in security surveillance and geophysical survey applications. The response of the DAS system to external vibrations varies with different types of fiber optic cable connections. The mechanism of mutual influence between the cable’s characteristics and DAS measurement results remains unclear. This study proposed a dynamic model of the interaction between the optical cable and the soil, analyzed the impact of the dynamic parameters of the optical cable and soil on the sensitivity of the DAS system, and validated the theoretical analysis through experiments. The findings suggest that augmenting the cable’s bending stiffness 5.5-fold and increasing its unit mass 4.2-fold result in a discernible reduction of the system’s response to roughly 0.15 times of its initial magnitude. Cables with lower unit mass and bending stiffness are more sensitive to vibration signals. This research provides a foundation for optimizing vibration-enhanced fiber optic cables and broadening the potential usage scenarios for DAS systems.

This article introduces an interrogation algorithm designed for low-cost tunable laser-based fiber Bragg grating (FBG) interrogation systems, specifically targeting general-purpose audio sensing. The algorithm leverages the inherent continuity and regularity present in acoustic signals by employing a prediction filter to forecast future samples. The algorithm determines the scan region based on the prediction and then acquires the narrowest optical bands that encompass solely the necessary information. Peak detection is performed on a subwindow of adaptive size. Compared with conventional full-band acquisition, the proposed algorithm has a much shorter laser engine scan path thus the overall sampling rate is augmented. Numerical simulations demonstrate a signal-to-noise ratio of 76.9 dB and an interrogation error of $\pm$ 9.747 pm (99.7% confidence) using properties of real-world optoelectronic devices and diversified audio samples. The algorithm presents consistent performance across audio content and a significant sampling rate improvement of maximum 40 times compared to conventional full-band scanning. The algorithm offers flexible configuration, hardware efficiency, and scalability for dynamic FBG sensing applications.

Addressing the critical need for vibration measurement in extreme cryogenic environments, this work introduces a novel cryogenic accelerometer integrating dual fiber Bragg gratings (FBGs), a seismic mass, an elliptic hinge, and a fixed base. We systematically derived the theoretical foundations governing its dynamic response parameters: sensitivity, natural frequency, and temperature-responsive performance of overall structure. A comprehensive theoretical model was developed, enabling simulation-based optimization to define its dynamic and thermal response performance. The cryogenic FBG accelerometer underwent rigorous test and characterization at both room temperature (293 K) and cryogenic conditions (83 K), as well as across the extensive 83–293 K thermal range. Experimental results closely aligned with theoretical predictions; the sensitivity exhibited a positive correlation with decreasing temperature, while the natural frequency exhibited an inverse relationship. Within the 83–293 K operational envelope, the accelerometer-maintained functionality across the 30–250 Hz bandwidth. The sensitivity values were quantified at 64.87 pm/g (293 K) and 68.17 pm/g (83 K). Demonstrating robust resilience to cross-axis effects, the maximum transverse interference measured was only 9.82% (293 K) and 9.71% (83 K). Deviations between the experimental and theoretical sensitivities were minimal (1.59% at 293 K, 5.44% at 83 K), as were those for the natural frequency (5.30% and 8.60%). 4J36 Invar alloy serves as the core structural material, which features a stable face-centered cubic crystal structure, an extremely low coefficient of thermal expansion (CTE), low thermal conductivity, and outstanding ductility and toughness, demonstrating exceptional suitability for measurement elements. Furthermore, the proposed cryogenic accelerometer delivers commendable dynamic response characteristics. Its compact form factor (45 $\times$ 25 $\times$ 15 mm) and lightweight (50 g) are complemented by the distinct advantage of enabling remote, simultaneous multipoint acceleration monitoring within ultracryogenic settings.

In remote or infrastructure-deficient areas, fiber grating demodulators typically rely on battery power, making low power consumption essential for prolonged field operation. To address this need, a low-power tunable laser-based fiber grating demodulator has been developed in this paper, employing a variable step-length laser scanning strategy based on OTSU threshold segmentation. By optimizing the scanning method, the field-programmable gate array (FPGA) clock frequency has been reduced to one-tenth of its original value while maintaining the demodulation frequency, achieving a 42.57% reduction in dynamic power consumption for the FPGA scanning control module. Experimental results demonstrate that the developed demodulator maintains a demodulation frequency of 2.5 kHz with a typical power consumption of only 2.43 W, significantly outperforming comparable market products. This demodulator’s exceptional low-power performance and stable demodulation capability provide a reliable technical solution for long-term field monitoring applications.