All-fiber vector bending sensor based on a four-core fiber

Area of Science:

• Fiber optics
• Optical sensing
• Interferometry

Background:

• Fiber optic sensors are crucial for measuring physical parameters.
• Existing sensors often lack directional sensitivity for bending.
• Mach-Zehnder interferometers offer high sensitivity but require precise fabrication.

Purpose of the Study:

• To develop and demonstrate a vector bending sensor using a four-core fiber.
• To investigate the sensor's performance in terms of sensitivity and directional discrimination.
• To evaluate the sensor's response to bending orientation and temperature variations.

Main Methods:

• Fabrication of a Mach-Zehnder interferometer by fusion splicing multimode fiber segments to a four-core fiber.
• Experimental characterization of the sensor's response to applied bending along different orientations.
• Measurement of bending sensitivity along principal axes and angular response.
• Assessment of temperature cross-sensitivity.

Main Results:

• The sensor demonstrated distinct sensitivities along two principal axes, reaching up to 91.342 nm/m⁻¹.
• Minimum and maximum sensitivities were recorded at 19.290 nm/m⁻¹ and 91.342 nm/m⁻¹, respectively.
• A periodic angular response of sensitivity was observed with varying bending orientation.
• Low temperature sensitivity of 0.077 nm/°C was achieved.

Conclusions:

• The proposed four-core fiber MZI sensor effectively enables vector bending measurement.
• The sensor exhibits excellent directional discrimination and repeatability.
• Its simple fabrication and robust performance make it suitable for advanced sensing applications.