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A novel fiber-optic vector magnetic field sensor and its sensing quality dependent of fabrication method has been proposed and investigated. The proposed sensor has two surfaces on the tip of a multimode fiber, which is used as the sensing probe. By plating different thickness of gold film on the surfaces, surface plasmon resonance (SPR) can be generated and the signal can be reflected by the surfaces as well. Meanwhile, magnetic fluid (MF) as the magnetic field sensitive material is packed around the sensing probe. The experimental results prove that the response of MF to external magnetic field can be used to sense magnetic field intensity and direction via monitoring the dip wavelength of SPR. The obtained refractive index (RI) sensitivities are 2105 nm/RIU (RI range: 1.332–1.365) and 6692 nm/RIU (RI range: 1.372–1.411), magnetic field intensity sensitivities are 11.67 nm/mT (0°), and −0.47 nm/mT (90°). Besides, the proposed sensing probe is ultracompact and the footprint is extremely small (the length of sensing part is only 615 μm), which is very helpful for magnetic field detection in narrow space and gradient field.

A kind of bent multimode fiber (MMF) vector magnetic sensor based on surface plasmon resonance (SPR) was proposed. By plating gold film on the curved part of the bent multimode fiber, the surface plasmon mode (SPM) was excited via a whispering gallery mode (WGM). Fabricating the structure only required bending the fiber and plating it with gold, which perfectly ensured the integrity of the fiber and made it more robust compared with other structures. The sensor used magnetic fluid (MF) as the magnetically sensitive material. Through monitoring the shift of the surface plasmon resonance dip, the as-fabricated sensor not only had a high magnetic field intensity sensitivity of 9749 pm/mT but could also measure the direction of a magnetic field with a high sensitivity of 546.5 pm/°. The additional advantages of the proposed sensor lay in its easy fabrication and good integrity, which make it attractive in the field of vector-magnetic-field sensing. [ABSTRACT FROM AUTHOR]

• Magnetic field and temperature sensing are realized with no core fiber coated with magnetic fluid and polydimethylsiloxane. • High sensitivity is obtained with the gold-clad no core fiber probe. • Reflection-like probe is convenient for magnetic field and temperature detection in narrow space. A kind of reflection-type magnetic field and temperature dual-parameter sensor based on surface plasmon resonance (SPR) effect was proposed and investigated. The sensing probe was fabricated with a section of no-core fiber, which was evenly divided into two parts. One part was immersed in magnetic fluid (MF) for magnetic field sensing (Channel 1, referred as CH1). The other part was coated with polydimethylsiloxane (PDMS) for temperature sensing (Channel 2, referred as CH2). The issue of magnetic field and temperature cross-sensitivity was resolved ingeniously. In the magnetic field intensity range of 0–55.1 mT, the maximum magnetic field sensitivity of 122.67 pm/mT was obtained. In the temperature range of 30–70 ℃, the maximum temperature sensitivity was 1662.64 pm/◦C. The sensor has the advantages of simple structure, small size, and potentials for applications in narrow space. [ABSTRACT FROM AUTHOR]

[Display omitted] • Comparative study of lab-on-fiber vector magnetic field sensor. • Magnetic field sensitivity based on few-mode fiber probe is higher than that based on multimode fiber one. • Magnetic fluid can be easily integrated with optical fiber to realize fiber-optic magnetic field sensor. • Few-mode fiber is more suitable for making fiber-tip magnetic field sensor than multimode fiber. • Reflection-type probe structure is beneficial for magnetic field sensing in narrow space. A kind of reflective vector magnetic field sensor with wedge-shaped fiber tip based on surface plasmon resonance (SPR) and magnetic fluid (MF) has been fabricated and investigated. Multimode fiber (MMF) and few-mode fiber (FMF) were grinded and polished to get the wedge-shaped fiber tip, which was then plated with nanoscale gold film for exciting SPR. The as-fabricated tip was immersed in MF, which was used as the magnetic field sensitive material. Experimental results show that the magnetic field intensity and direction sensitivities of the magnetic field sensors based on MMF and FMF are 2317 pm/mT, 497 pm/° and 6776 pm/mT, 2313 pm/° respectively, which proves that the proposed sensor based on wedge-shaped fiber tip has great potential for realizing lab-on-fiber devices and applications. [ABSTRACT FROM AUTHOR]

A kind of symmetric side-polished photonic crystal fiber is designed for sensing application based on the surface plasmon resonance technology. The finite element method is used to study the influence of structural parameters on the sensing performance. The average wavelength sensitivity (WS) is 2380 nm/RIU for the refractive index ranging from 1.340 to 1.380, and the average WS is 6260 nm/RIU when the refractive index changes from 1.380 to 1.406. The maximum WS at refractive index of 1.406 is 9333 nm/RIU. Furthermore, the polydimethylsiloxane and magnetic fluid are used as the temperature and magnetic field sensitive materials, respectively. Simultaneous measurement of magnetic field and temperature is realized. The magnetic field and temperature sensitivities are 0.60 nm/mT and -4.09 nm/°C, respectively. The designed scheme solves the problem of temperature cross-sensitivity of the magnetic field sensor. [ABSTRACT FROM AUTHOR]

A simple hetero-core optical fiber (MMF-NCF-MMF) surface plasmon resonance (SPR) sensing structure was proposed. The SPR spectral sensitivity, full width of half peak (FWHM), valley depth (VD), and figure of merit (FOM) were defined to evaluate the sensing performance comprehensively. The effect of gold film thickness on the refractive index and temperature sensing performance was studied experimentally. The optimum gold film thickness was found. The maximum sensitivities for refractive index and temperature measurement were obtained to be 2933.25 nm/RIU and −0.91973 nm/°C, respectively. The experimental results are helpful to design the SPR structure with improved sensing performance. The proposed SPR sensing structure has the advantages of simple structure, easy implementation, and good robustness, which implies a broad application prospect. [ABSTRACT FROM AUTHOR]