Low cross-sensitivity and sensitivity enhanced FBG sensor based on OCMI with three cascaded FBGs

Area of Science:

• Photonics and Optical Sensing
• Interferometry
• Fiber Optic Sensors

Background:

• Traditional optical sensing methods often face limitations in sensitivity and temperature cross-sensitivity.
• The Vernier effect offers a way to enhance sensor sensitivity but can be further improved.
• Developing robust and highly sensitive sensors is crucial for various applications.

Purpose of the Study:

• To present a highly sensitive and temperature-insensitive optical carrier microwave interferometry (OCMI) system.
• To achieve an enhanced Vernier effect for improved sensing performance.
• To demonstrate the system's effectiveness in strain sensing applications.

Main Methods:

• Utilizing a cascaded three fiber Bragg grating (FBG) structure.
• Generating an enhanced Vernier effect by superimposing interferograms from two separate interferometers.
• Experimental and theoretical analysis of strain and temperature sensitivity.

Main Results:

• Achieved a strain sensitivity of -4.642 MHz/µε, significantly higher than single interferometers.
• Demonstrated a substantial reduction in temperature sensitivity to -71.384 kHz/°C.
• Showcased adjustable amplification factors by altering the spatial distance between FBGs.

Conclusions:

• The proposed OCMI system with an enhanced Vernier effect offers superior sensitivity and temperature compensation.
• The sensor exhibits high resolution, high sensitivity, and low cross-sensitivity.
• This technology holds great potential for measuring small physical changes in complex environments.