Different from usually-used bulk magnetostrictive materials, magnetostrictive TbDyFe thin films were firstly proposed as sensing materials for fiber-optic magnetic field sensing characterization. By magnetron sputtering process, TbDyFe thin films were deposited on etched side circle of a fiber Bragg Grating (FBG) as sensing element. There exists more than 45pm change of FBG wavelength when magnet field increase up to 50 mT. The response to magnetic field is reversible, and could be applicable for magnetic and current sensing.

In this paper, a novel optical fiber temperature sensor based on surface plasmon resonance (SPR) is presented. The sensor consists of multimode fiber-photonic crystal fiber-multimode fiber (MMF-PCF-MMF) structure coated with gold film, whose refractive index (RI) sensitivity was found to range from 1060.78 nm/RIU to 4613.73 nm/RIU in the RI range of 1.3330-1.3904. Through simulation and experimental results, the RI sensitivity of the MMF-PCF-MMF structure is found to be higher than that of multimode fiber-single mode fiber-multimode fiber (MMF-SMF-MMF) structure. The sensing area was coated with polydimethylsiloxane (PDMS) that has a high thermal coefficient, obtaining a high temperature sensitivity of −1.551 nm/°C in the temperature range of 35-100 °C, which means it has a broad application prospect in medical, environmental monitoring and manufacturing industry.

Fiber Bragg grating (FBG) array is a powerful technique for quasi-distributed sensing along the entire length of sensing fiber with fast response and high precision. It has been widely used for temperature, strain, and vibration monitoring. In this review work, an overview on the recent advances of FBG arrays is conducted. Firstly, the fabrication methods of FBG array are reviewed, which include femtosecond laser system and online writing technique. Then, the demodulation techniques for FBG arrays are presented and discussed. Distributed static sensing can be performed by demodulating wavelength shift of each FBG, while phase demodulation techniques with low noise are employed for dynamic vibration sensing. Simultaneous distributed dynamic and static sensing system based on FBG array is also outlined. Finally, possible future directions are discussed and concluded. It is believed that the FBG array has great development potential and application prospect.

WO₃ -Pd composite films were deposited on the side-face of side-polished fiber Bragg grating as sensing elements by magnetron sputtering process. XRD result indicates that the WO₃ -Pd composite films are mainly amorphous. Compared to standard FBG coated with same hydrogen sensitive film, side-polished FBG significantly increase the sensor’s sensitivity. When hydrogen concentrations are 4% and 8% in volume percentage, maximum wavelength shifts of side-polished FBG are 25 and 55 pm respectively. The experimental results show the sensor’s hydrogen response is reversible, and side-polished FBG hydrogen sensor has great potential in hydrogen’s measurement.

Optical fiber hydrogen sensor has become a research hotspot once proposed, since its unique properties of intrinsic safety. In the past three decades, varieties of optical fiber hydrogen sensors have been proposed, which could be categorized into five types, including interference type, micromirror type, evanescent field type, surface plasmon resonance type, and fiber Bragg grating type. This review focuses on the representative of the above five types of hydrogen sensors, based on Pd alloy or/and WO ₃ sensitive materials. Whereas, their structures, characteristics, and sensing performances are critically overviewed.

In this letter, a simultaneous measurement system of temperature and relative humidity is proposed, which consists of a fiber Bragg grating (FBG) and Fabry-Perot (FP) interferometer. The FP interferometer was fabricated by splicing the hollow capillary with a single-mode fiber and the end of the hollow capillary was filled with a layer of polyimide, achieving a humidity sensitivity of 22.07 pm/%RH in the range of 20-90 %RH. FBG is insensitive to humidity, which can be used to measure temperature and eliminate the obstruction of temperature on FP humidity probe by formula conversion. The temperature sensitivity of FBG is 9.98 pm/°C. Due to low cost and good stability, this system has broad application prospects in the fields of food processing, medical care, and food storage.