Highly sensitive curvature sensor based on a sandwich multimode fiber Mach-Zehnder interferometer

Area of Science:

• Optoelectronics and Photonics
• Fiber Optic Sensors
• Interferometry

Background:

• Mach-Zehnder interferometers are widely used for sensing applications.
• Developing highly sensitive and selective curvature sensors remains a challenge.
• Existing sensors may suffer from temperature cross-sensitivity.

Purpose of the Study:

• To propose and demonstrate a novel optical fiber Mach-Zehnder interference curvature sensor.
• To investigate the sensor's principle, structural parameter influences, and performance.
• To achieve temperature-independent curvature sensing.

Main Methods:

• Fabrication of a MMF-GIMMF-MMF (multimode fiber-graded index multimode fiber-multimode fiber) structure.
• Splicing graded-index multimode fiber (GIMMF) between two short stepped-index multimode fibers (SIMMFs).
• Theoretical analysis of sensing principle and structural parameter effects on interference spectrum.
• Experimental characterization of sensitivity to bending and temperature.

Main Results:

• The sensor generates interference spectra from core-cladding mode interaction in short GIMMFs.
• Interference valley intensity is highly sensitive to curvature but insensitive to temperature.
• Dip wavelength shows low sensitivity to bending but high sensitivity to temperature.
• Maximum curvature sensitivity of -78.75 dB/m^-1 achieved in a 0-2.36 m^-1 range.
• Sensor length can be as short as 3 mm.

Conclusions:

• A compact, temperature-independent optical fiber curvature sensor is realized by monitoring interference valley intensity.
• The sensor's design offers high sensitivity and good reproducibility.
• The proposed sensor is suitable for bending-related high-precision engineering applications.