Refractometer based on fiber Mach-Zehnder interferometer composed of two micro bending cores

Area of Science:

• Photonics and Optical Sensing
• Fiber Optic Sensors
• Interferometry

Background:

• Mach-Zehnder Interferometers (MZI) are sensitive optical devices.
• Fiber optic sensors offer advantages in harsh environments.
• Accurate simultaneous measurement of refractive index (RI) and temperature is crucial in various applications.

Purpose of the Study:

• To propose and experimentally validate a novel refractometer based on a Mach-Zehnder Interferometer (MZI).
• To enhance refractive index (RI) sensitivity by exciting higher-order cladding modes.
• To enable simultaneous measurement of RI and temperature using a single fiber optic sensor.

Main Methods:

• Fabrication of a Mach-Zehnder Interferometer (MZI) using 2 micro bending cores (MBCs) via CO2 laser polishing and oxyhydrogen flame heating.
• Excitation and coupling of cladding modes within the MBC structure to enhance light-matter interaction.
• Experimental measurement of RI and temperature sensitivities using transmission dips at specific wavelengths.

Main Results:

• Achieved high RI sensitivities of -271.7 nm/RIU and -333.8 nm/RIU for the refractive index (RI) range of 1.33-1.42.
• Obtained temperature sensitivities of 0.121 nm/℃ and 0.171 nm/℃ within the temperature range of 34℃-154℃.
• Demonstrated the capability for simultaneous RI and temperature measurement by solving a matrix equation.

Conclusions:

• The proposed MZI-based fiber optic sensor exhibits excellent sensitivity for refractive index (RI) and temperature.
• The unique fabrication method enhances the interaction between the fiber core and external conditions, leading to improved performance.
• The sensor is suitable for simultaneous measurement of RI and temperature, offering a versatile sensing solution.