In-fiber Mach-Zehnder interferometer based on hollow optic fiber for metal ion detection

Area of Science:

• Fiber optic sensing
• Chemical sensors
• Environmental monitoring

Background:

• Copper ions (Cu²⁺) are common environmental contaminants.
• Accurate detection of Cu²⁺ is crucial for water quality assessment.
• Existing detection methods can be complex or costly.

Purpose of the Study:

• To propose and demonstrate a new in-fiber Mach-Zehnder interferometric sensor for Cu²⁺ detection.
• To develop a simple, cost-effective, and sensitive sensor for aqueous environments.
• To evaluate the sensor's performance, reusability, and repeatability.

Main Methods:

• Fabrication of an in-fiber Mach-Zehnder interferometer by arc-fusing hollow optical fiber between single-mode fibers.
• Functionalization of the sensor using chitosan and poly(acrylic acid) bilayers via electrostatic self-assembly.
• Experimental characterization of sensor response to varying Cu²⁺ concentrations.

Main Results:

• The sensor demonstrated a linear response to Cu²⁺ concentration from 0 to 40 µM.
• Achieved a high sensitivity of 42 nm/mM.
• Exhibited excellent reusability and repeatability over multiple detection cycles.

Conclusions:

• The proposed fiber optic sensor is a promising tool for detecting Cu²⁺ ions.
• The sensor's simplicity, cost-effectiveness, and performance make it suitable for real-world water quality monitoring.
• Potential applications include detecting contamination in drinking water and industrial wastewater.