All-fiber Mach-Zehnder interferometers for sensing applications

Area of Science:

• Photonics and Optical Sensing
• Fiber Optic Interferometry
• Nanofabrication

Background:

• Mach-Zehnder interferometers (MZIs) are crucial for sensing.
• Existing fiber optic sensors often require complex fabrication.
• There is a need for versatile, cost-effective fiber optic sensors.

Purpose of the Study:

• To propose and demonstrate a novel thinned fiber based Mach-Zehnder interferometer.
• To achieve multi-purpose sensing capabilities including liquid level and refractive index.
• To develop a simple and cost-effective fabrication method.

Main Methods:

• Fabrication of a sensor head using an all-fiber in-line singlemode-multimode-thinned-singlemode (SMTS) structure via splicing.
• Utilizing the interference between thinned fiber cladding modes and the core mode, with a multimode fiber as a mode coupler.
• Measuring wavelength shifts and sensitivity for different measurands.

Main Results:

• Simultaneous measurement of liquid level and refractive index.
• Achieved water level sensitivity of -175.8 pm/mm and refractive index sensitivity of -1868.42 (pm/mm)/RIU.
• Demonstrated refractive index sensitivity of -25.2935 nm/RIU, temperature sensitivity of 0.0615 nm/°C, and axial strain sensitivity of -2.99 pm/με.

Conclusions:

• The thinned fiber MZI offers a novel and simple approach for multi-purpose sensing.
• The sensor exhibits high sensitivity for various parameters, including liquid level and refractive index.
• The fabrication process is cost-effective and suitable for practical applications.