Ultrahigh-sensitivity triple-parameter sensor based on dual-capillary spliced fiber for simultaneous detection of magnetic field, temperature, and relative humidity

An ultrahigh-sensitivity triple-parameter sensor based on dual-capillary spliced fiber (DCSF) is proposed for simultaneous detection of magnetic field, temperature, and relative humidity. The DCSF is constructed by using two notched capillaries symmetrically arranged on both sides of a Ge-doped core. By filling magnetic fluid (MF) and polydimethylsiloxane (PDMS) into the two capillaries respectively, and depositing polyvinyl alcohol (PVA) on the exterior of the DCSF, the sensor is constructed to achieve synchronous detection of the three parameters. Three Al wires are positioned at the special positions of core to excite surface plasmon resonance (SPR) effect, thereby significantly enhancing the sensitivities. Systematic optimization of structural parameters endows the sensor with superior sensing performance. Numerical results demonstrate that the sensor can simultaneously detect the magnetic field ranging from 35 Oe to 120 Oe, the temperature from 14.3℃ to 99.3℃, and the relative humidity from 30% to 80%. The maximum magnetic field sensitivity, maximum temperature sensitivity, and maximum relative humidity sensitivity reach 120,000 pm/mT, 4.8 nm/°C and 63.2 nm/%RH, respectively. Notably, the maximum magnetic field and maximum relative humidity sensitivities are more than two orders of magnitude higher than those of most similar researches, while the maximum temperature sensitivity is comparable to results from existing studies. Particularly, the positions of the three Al wires exhibit a negligible influence on the sensitivities. With the advantages including ultrahigh sensitivity, a wide detection range, easy filling of sensitive media, and a high degree of freedom in Al wire positioning, the DCSF-based triple-parameter sensor has enormous application potential in complex environmental monitoring, national defense, aerospace, and other critical fields.