RESUMO
Optical fiber extrinsic Fabry-Perot interferometers (EFPIs) have been extensively demonstrated for the measurement of displacement and displacement-related physical quantities, e.g., acceleration, pressure, with high sensitivity and resolution. Despite its wide and successful applications, a conventional EFPI is limited to measuring only one-dimensional (out-of-plane) movement of its external reflector. In this Letter, a new strategy for optical fiber sensing, particularly for EFPI sensing, is proposed and demonstrated, allowing for three-dimensional (3-D) measurements based on a hybrid and compact EFPI device. A 3-D integrated optical waveguide array is aligned against a lead-in optical fiber with an air gap, where an EFPI is formed by the end facet of the optical fiber and the end facet of the waveguide array. As a proof of concept, we experimentally demonstrate that 3-D positioning can be achieved from the EFPI with sub-micron resolution by simultaneously measuring the reflection and transmission of the device. The proposed strategy of using an optical waveguide as an external reflector for an optical fiber EFPI, combined with machine learning-based analysis, opens new avenues in the development of compact yet multi-dimensional sensors.
RESUMO
A 3-aminopropyl-triethoxysilane (APES) fiber-optic sensor based on a Mach-Zehnder interferometer (MZI) was demonstrated. The MZI was constructed with a core-offset fusion single mode fiber (SMF) structure with a length of 3.0 cm. As APES gradually attaches to the MZI, the external environment of the MZI changes, which in turn causes change in the MZI's interference. That is the reason why we can obtain the relationships between the APES amount and resonance dip wavelength by measuring the transmission variations of the resonant dip wavelength of the MZI. The optimized amount of 1% APES for 3.0 cm MZI biosensors was 3 mL, whereas the optimized amount of 2% APES was 1.5 mL.