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.

This paper presents a hermitic fiber sensor packaging technique that enables fiber sensors to be embedded in energy systems for performing multi-parameter measurements in high-temperature and strong radiation environments. A high-temperature stable Intrinsic Fabry–Perot interferometer (IFPI) array, inscribed by a femtosecond laser direct writing scheme, is used to measure both temperature and pressure induced strain changes. To address the large disparity in thermo-expansion coefficients (TECs) between silica fibers and metal parts, glass sealants with TEC between silica optical fibers and metals were used to hermetically seal optical fiber sensors inside stainless steel metal tubes. The hermetically sealed package is validated for helium leakages between 1 MPa and 10 MPa using a helium leak detector. An IFPI sensor embedded in glass sealant was used to measure pressure. The paper demonstrates an effective technique to deploy fiber sensors to perform multi-parameter measurements in a wide range of energy systems that utilize high temperatures and strong radiation environments to achieve efficient energy production.

This paper presents a rapid prototyping method for fabricating double-sided tape-based microfluidic chips that address limitations in material flexibility, fabrication complexity, and on-chip functionalities. The approach employs biocompatible, low-cost materials—including medical-grade tapes, rubber, and thermoplastics (PMMA, polycarbonate, polystyrene)—micromachined via femtosecond lasers. Solvent- and heat-free tape-based bonding enables efficient fabrication of optically transparent, UV-sterilizable layers for biomedical applications. The method supports integrated on-chip pumps and active/passive valves, achieving bidirectional and multidirectional flow control with minimal external actuation. These components operate at up to 14 psi actuation pressure and $230~\mu $ L/min flow rates, adaptable via chamber dimensions. A dual-pump configuration mimics peristaltic pumping for continuous flow, while a prototype with multidirectional pumps and reservoirs demonstrates dynamic fluid routing and on-demand distribution. The technique offers a versatile, scalable solution for microfluidic applications requiring sterility, optical clarity, and on-chip fluidic control. [2025-0059]

This paper describes a low-cost fiber optical temperature sensor technology with wide operation temperature ranges and immune to complex electromagnetic environments. Using a low-cost passive frequency-double Q-switch YAG laser as the excitation source, multi-point fiber optical temperature sensors based on Raman backscattering are demonstrated. Using CCD cameras as optical sensors to detect both Stokes and Anti-Stokes backscattering signal, this paper shows that a 176-μW excitation optical power coupled into optical fiber is sufficient to perform accurate temperature measurement. The temperature sensors are calibrated against thermocouple sensors from 20 °C to 120 °C with temperature measurement mean square errors better than 2 °C. The technology described in this paper is particularly suitable for renewable energy applications such as battery monitoring.