Multipoint fiber optics refractive index sensor based on multimode interference effects.

Area of Science:

• Optics and Photonics
• Sensing Technologies
• Materials Science

Background:

• Refractive index measurement is crucial for analyzing liquid properties.
• Existing methods often lack spatial multiplexing capabilities.
• All-fiber sensing offers robustness and miniaturization potential.

Purpose of the Study:

• To develop and validate a fiber optic sensing structure for simultaneous, multi-point refractive index measurement.
• To demonstrate the feasibility of using parallel multimodal interference (MMI) devices for this application.
• To enable real-time monitoring of liquid compositions at different locations.

Main Methods:

• Fabrication of an all-fiber sensing architecture using standard single-mode-multimode-single-mode (SM-MM-SM) MMI devices.
• Engineering spectral responses of parallel MMI devices for non-overlapping interrogation.
• Utilizing a single broadband light source and optical spectrum analyzer for system interrogation.
• Conducting proof-of-concept experiments with aqueous saline, water-glycerol, and water-ethylene glycol solutions.

Main Results:

• Successful demonstration of simultaneous refractive index measurement at multiple spatial locations.
• Validation of the non-overlapping spectral response engineering for parallel MMI devices.
• Accurate refractive index determination for various liquid samples, including binary solutions.
• Confirmation of the proposed platform's capability for simultaneous monitoring.

Conclusions:

• The developed fiber optic sensing structure effectively enables simultaneous, multi-point refractive index measurements.
• The parallel MMI device architecture offers a robust and efficient solution for liquid analysis.
• This technology holds promise for applications requiring spatially resolved monitoring of liquid properties.