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• Proposed an optical fiber sensor for salinity and temperature simultaneous measurement based on dual SPR effect. • SPR effect is generated by coating dual hole single mode fiber with Au film. • Proposed sensor is with high sensitivity and stability. Seawater salinity is a fundamental parameter of the marine environment. This manuscript introduces a novel fiber optic sensor utilizing dual SPR effect, which is experimentally demonstrated. The sensor is made by fusion splicing Dual-Hole Single-Mode Fiber (DHSMF) that incorporates two sections of multimode fiber (MMF). A gold film is deposited on one section of the DHSMF to induce the surface plasmon resonance (SPR) phenomenon. One half of the sensing area is coated with polydimethylsiloxane (PDMS) as the thermally responsive material. The other half of the sensing area remains uncoated to generate double SPR phenomenon, the double SPR spectrum is adopted for salinity and temperature simultaneously detection. Experimental results reveals that sensitivity of salinity and temperature are 0.33 nm/‰ and 2.82 nm/°C. Furthermore, the sensor presents superior reversibility and stability. The high performance and compact structure making proposed sensor suitable for detecting seawater salinity and temperature simultaneously. [ABSTRACT FROM AUTHOR]

A high-sensitivity temperature sensor based on reflective Solc-like filter with Vernier effect has been proposed and experimentally investigated in this article. The reflective Solc-like filter is composed of a polarizer and the cascaded polarization maintaining fibers (PMFs) of similar length, which is a kind of all-fiber polarization interference filter. The gold film is coated in the end of the longer PMF to improve the reflectivity of the filter. The mathematical model of the reflective Solc-like filter has been built by the Jones matrix. The simulation results show that the main factor affecting the temperature sensitivity is the length of the PMF fiber, and the fringe visibility of the spectral fringes is only related to splice angles. Experiment results indicate that the Solc-like filter exhibits a high sensitivity of −44.27 nm/°C, which is enlarged over 25 times compared with that of the reflective Solc filter with single PMF, and the temperature resolution can reach $4.5\times 10^{{-4{ }}\,\circ }\text{C}$. To the best of our knowledge, this is the first demonstration that the cascaded PMFs have been applied to the reflective filter, which provides high reference value for the application of polarization interference filters in the sensing field. [ABSTRACT FROM AUTHOR]

• An optical fiber temperature sensor employing the vernier effect is presented. • The sensor has low production cost, simple fabrication, and small volume. • The sensor has good stability and repeatability. • It provides a new approach for in-depth research on temperature monitoring. This paper introduces a optical fiber temperature sensor based on vernier effect. The sensor's design consists of two integrated interferometric structures: the Mach-Zehnder interferometer (MZI) and the Fabry-Perot interferometer (FPI). Both interferometric structures exhibit symmetry, but they employ different types of optical fibers. Specifically, the MZI employs dual side hole fiber (DSHF), while the FPI is constructed using hollow-core optical fibers.Given the MZI's superior sensitivity to temperature changes compared to the FPI, it is chosen as the sensing arm. The paper conducts theoretical research and experimental validation of the optical fiber sensor's sensing principles. The findings reveal a sensor sensitivity of −305.42 pm/°C when measuring temperatures within the 32–50 °C range. Stability testing, repeatability testing, and response time testing are carried out using a constant temperature chamber and a water bath, affirming the sensor's excellent repeatability and stability, along with a response time faster than that of conventional thermometers. [ABSTRACT FROM AUTHOR]

• This manuscript presents an integrated sensor can be replicated to other dual parameter simultaneous. • The proposed sensor adopts different principles for detection, which is easy to overcome the complexity of data demodulation. • The sensitivity of salinity and temperature is 429.72 pm/%R and −316.72 pm/℃ respectively. Simultaneous detection of seawater salinity and temperature is conductive to study the state of seawater more intuitively. In this manuscript, a sensor for seawater salinity and temperature simultaneous measurement based on surface Plasmon resonance (SPR) and Mach-Zehnder interference (MZI) is put forward. The sensor forms MZI by fusing multimode fiber at both ends of hollow core fiber, SPR is formed by gold plating on one side of the hollow core fiber, and then MZI and SPR are coupled in a sensing structure. Experimental results reveal that the sensitivity of seawater temperature is −316.72 pm/℃ with temperature changing from 20 ℃ to 45 ℃, and the sensitivity of seawater salinity is 429.72 pm/‰. The proposed sensor overcomes the measurement error caused by the spatial position difference of cascade sensors, and provides a new idea for double parameter detection. What's more, the sensor presents the advantages of small volume, simple fabrication and excellent performance. [ABSTRACT FROM AUTHOR]

Surface plasmon resonance (SPR) technology has effectively bolstered optic fiber sensing in fields of life science, clinical diagnosis, medicine, food safety and so on. The current review outlines the research status of fiber optic biosensor based on SPR, and the merits of optical fiber sensor and the development of optical fiber sensor based on SPR are completely covered. An in-depth review of four devices for generating SPR is presented, and optical fiber is finally adopted for a substrate to generate SPR. Different prototypes of optical fiber biosensor based on SPR are meticulously outlined: optical fiber grating biosensor based on SPR and optical fiber structured type biosensor based on SPR, and representative instances from literature are presented to verify the latest advancements in this potentially valuable research avenue. In addition, the sensing performance of different optical fiber structured type biosensor based on SPR are compared. What's more, simultaneous multi-parameter detection and improvement of sensitivity are discussed and summarized. The article concludes identify key challenges and develop orientation of optical fiber biosensor based on SPR. • This paper reviews the research status of fiber optic biosensors based on SPR. • Firstly, the SPR generation methods are systematically summarized. • The fiber grating biosensor and the optical fiber biosensor which can produce SPR effect are analyzed. • The double or multi-parameter measurement of SPR-based optical fiber biosensor is analyzed. [ABSTRACT FROM AUTHOR]

An optical fiber axial contact force sensor based on bubble-expanded Fabry–Pérot interferometer (FPI) is investigated in this paper. The FPI is packaged as a reflective sensing probe to measure the axial contact force which is applied on the end of sensing probe. To the best of the authors’ knowledge, this is the first time that intrinsic optical fiber FPI is used for axial contact force measurement, which has potential in application fields such as robotics. The sensing probe based on bubble-expanded FPI exhibits a high axial contact force measurement sensitivity of −750.17 pm/N, which is 3 times higher than that of the sensing probe based on traditional rectangular FPI fabricated in this work. This experimental results are well explained by the simulation analysis using Comsol software. The proposed optical fiber axial contact force sensor has advantages of compact size, simple structure and high sensitivity. [ABSTRACT FROM AUTHOR]