Simultaneous measurement of magnetic field and temperature based on an etched TCFMI cascaded with an FBG

•In this paper, we present a dual-parameter sensing scheme based on an etched TCFMI cascaded with an FBG for simultaneous magnetic field and temperature monitoring.•The investigation of the magnetic field and temperature responses of the MF packaged TCFMI was first carried out, which show a highly enhanced magnetic field intensity sensitivity and an unnegligible temperature-cross sensitivity at 1550 nm.•Due to the different responses of the reflection and Bragg wavelength to temperature and magnetic field, by using the sensing matrix method, the simultaneous measurement of temperature and magnetic field intensity can be realized.•Meanwhile the reflective sensing probe type is more compact and practical for applications in hard-to-reach conditions.

In this paper, a dual-parameter measurement scheme based on an etched thin core fiber modal interferometer (TCMI) cascaded with a fiber Bragg grating (FBG) is proposed and experimentally demonstrated for simultaneous measurement of magnetic field and temperature. The magnetic field and temperature responses of the packaged TCFMI were first investigated, which showed that the magnetic field sensitivity could be highly enhanced by decreasing of the TCF diameter and the temperature-cross sensitivities were up to 3–7 Oe/°C at 1550 nm. Then, the theoretical analysis and experimental demonstration of the proposed dual-parameter sensing scheme were conducted. Experimental results show that, the reflection of the FBG has a magnetic field intensity and temperature sensitivities of −0.017 dB/Oe and 0.133 dB/°C, respectively, while the Bragg wavelength of the FBG is insensitive to magnetic field and has a temperature sensitivity of 13.23 pm/°C. Thus by using the sensing matrix method, the intensity of the magnetic field and the temperature variance can be measured, which enables magnetic field sensing under strict temperature environments. In the on–off time response test, the fabricated sensor exhibited high repeatability and short response time of ∼19.4 s. Meanwhile the reflective sensing probe type is more compact and practical for applications in hard-to-reach conditions.