Temperature-immune Fabry-Perot cavity sensor based on an opened hollow-core anti-resonant fiber

A new approach to conquer the thermal phase drift of an optical fiber Fabry-Perot interferometer (FPI) sensor is proposed and experimentally demonstrated. By employing a hollow-core anti-resonant fiber (HC-ARF) and optimizing the fusion splicing (includes mode field adaptation) between the lead-in single-mode fiber (SMF) and the HC-ARF, a high spectral resolution (lambda/ increment lambda approximate to 3.8 x 104) optical fiber air-cavity FPI sensor with a fringe visibility higher than 7 dB is constructed. To eliminate the thermal phase drift (i.e. temperature crosstalk) of the sensor that originates from the intrinsic thermal expansion effect of the silica material of the HC-ARF, the FPI air cavity is connected to the external environments, by which the effect of air expelling from the cavity with temperature increasing can well compensate the temperature-induced cavity elongation. As a result, the thermal phase drift of the FPI is reduced to zero at a temperature range of similar to 80-110 degrees C and within the temperature range of 40-80 degrees C, the thermal phase drift is still halved compared with the sealed FPI cavity. The nearly zero thermal phase drift of a FPI at such a temperature range has never been achieved before, to our best knowledge. As a proof of concept, a temperature-immune fiber-optic strain sensor is demonstrated. This work offers a new and efficient approach to eliminate the thermal phase drift (i.e. temperature crosstalk) of a fiber-optic device, which may significantly improve the measurement accuracy and detection limit of fiber-optic FPI sensors. Furthermore, the principle and schema can be generalized to a wide variety of fiber-optic devices.

Automated summary

A new approach is proposed to conquer the thermal phase drift of fiber-optic Fabry-Perot interferometer (FPI) sensors. By using a hollow-core anti-resonant fiber and optimizing the fusion splicing between the lead-in single-mode fiber and the hollow-core anti-resonant fiber, a high spectral resolution FPI sensor is constructed. The thermal phase drift of the FPI is eliminated by connecting the FPI air cavity to the external environments, leading to improved measurement accuracy and detection limit.