The Thermo-Optic Discrimination of an Aqueous Solution Composition Using a Multimodal Interference Fiber Optic Sensor
Year: 2025
Type: conference-paper
Abstract: Fiber optics sensors based on multimodal interference (MMI) have proven effective for refractometry of liquid samples. Here, we extend these capabilities to demonstrate that aqueous solutions with a similar refractive index (RI), which at room temperature are indistinguishable at the same concentration, can be discriminated against based on their thermo-optical response. We used an MMI sensor with the standard singlemode–multimode–singlemode architecture, where a section of no-core multimode fiber provides environmental sensitivity to the fiber surroundings. The proposed idea has been tested on aqueous solutions of tris and fructose, whose RI has a similar dependence on concentration. Indeed, we verified that they produce indistinguishable wavelength shifts as a function of concentration, measuring 0.2179 nm/% for tris and 0.2264 nm/% for fructose. Then, by varying the temperature in a controlled manner, from 25 °C to 45 °C in 2.5 °C increments, the distinct thermo-optic response can be unveiled for the two samples, which now permits differentiating them. Thermal sensitivities of 0.14433 nm/°C for tris and 0.1852 nm/°C for fructose were observed. This optical sensor requires no specific preparation or specialized equipment because the temperature range needed to achieve thermo-optical discrimination is accessible. Therefore, the measurement protocol can be incorporated into commercial refractometers equipped with temperature control.
Language: English
Topic: Advanced Fiber Optic Sensors
Subfield: Electrical and Electronic Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: gold
OpenAlex ID: W4409894583