Cascaded multicore fiber interferometers for enhanced bending sensing based on the Vernier effect

Area of Science:

• Fiber optics
• Optical sensing
• Interferometry

Background:

• Modal interferometers are crucial for sensing applications.
• Strongly-coupled seven-core fiber (SC-SCF) offers unique optical properties.
• The Vernier effect can amplify small spectral shifts.

Purpose of the Study:

• To demonstrate cascaded modal interferometers using SC-SCF for enhanced bending sensing.
• To leverage the Vernier effect for improved sensitivity.
• To investigate the sensor's performance and advantages.

Main Methods:

• Fabrication of cascaded modal interferometers using SC-SCF with different lengths.
• Utilizing two SC-SCF interferometers (sensor and reference) with distinct free spectral ranges (FSRs).
• Analyzing the wavelength shift of the output spectrum's envelope.

Main Results:

• The Vernier effect significantly amplifies the wavelength shift compared to a single interferometer.
• Bending sensitivity is enhanced from -2.20 nm/m⁻¹ (single SC-SCF) to 42.32 nm/m⁻¹ (cascaded SC-SCF).
• The sensor exhibits high sensitivity, ease of fabrication, and low cost.

Conclusions:

• Cascaded SC-SCF interferometers effectively enhance bending sensing sensitivity.
• The proposed sensor is suitable for high-precision bending measurement applications.
• This technology offers a cost-effective and practical solution for advanced sensing.