In-line fiber optic optofluidic sensor based on a fully open Fabry-Perot interferometer

TL;DR

This paper introduces an economical, robust, and fully open fiber optic Fabry-Perot interferometer designed for fluidic sensing, demonstrating high sensitivity and ease of fabrication suitable for practical optofluidic applications.

Contribution

The paper presents a novel fully open fiber optic FPI sensor with a simple fabrication process, high sensitivity, and potential for mass production in optofluidic sensing.

Findings

Achieved over 20 dB visibility in fabrication.

Sensor sensitivity exceeds 1116 nm/RIU.

Temperature stability varies with bonding method.

Abstract

We present an all-fiber, fully open Fabry-Perot interferometer (FPI) cavity that is suitable for fluidic measurement applications. Fabrication of the FPI involves the alignment and bonding of three optical fiber sections using either ceramic glue or low-temperature melting glass. The fabrication procedure allows the protection of the cleaved optical fiber end faces, which serve as the two mirrors of the FPI, from damage, thus ensuring the high visibility of the FPI sensor. The FPI's complete openness permits the analyte of interest fluids to flow smoothly into the cavity and interact directly with the light, obviating the need for additional assistance. The fabrication experiment demonstrates that the fabrication procedure can readily achieve a visibility of over 20 dB. Refractive index testing indicates that the sensor exhibits a sensitivity of over 1116 nm/RIU within the range of 1.334-1.375. A comparison of temperature investigations indicates that the fully open cavity FPI fabricated by bonding with low-temperature melting glass exhibits relatively lower temperature immunity than that bonded with ceramic glue. Both have a relatively low temperature fluctuation within the temperature range of 40{\deg}C-100{\deg}C, with less than 3 nm and 4.5 nm in the over 60{\deg}C changes, respectively. Our proposed fully open FPI is an economical, robust, and simple-to-fabricate structure with the potential for mass production. This renders it an appealing option for practical optofluidics applications.