Compact fiber-optic curvature sensor based on super-mode interference in a seven-core fiber.

Area of Science:

• Optoelectronics
• Fiber Optics Sensors
• Nanotechnology

Background:

• Optical fiber sensors are crucial for measuring physical parameters.
• Existing sensors often face limitations in sensitivity, size, or loss.
• Developing compact and highly sensitive curvature sensors is an active research area.

Purpose of the Study:

• To present a compact, low loss, and highly sensitive optical fiber curvature sensor.
• To investigate the sensor's response to bending, temperature, and external refractive index.
• To demonstrate the sensor's interrogation capabilities using spectral shift and visibility changes.

Main Methods:

• Fabrication of a sensor using a short segment of seven-core fiber spliced between single-mode fibers.
• Analysis of transmission spectrum changes under straight and bent conditions.
• Experimental characterization of sensitivity, dynamic range, and environmental effects.

Main Results:

• A pronounced interference pattern was observed in the transmission spectrum of the straight fiber.
• Bending induced a spectral shift and altered interference notch visibility.
• A linear sensitivity of approximately 3000 nm/mm⁻¹ for bending was experimentally achieved.
• The dynamic range is tailorable by adjusting the seven-core fiber length.

Conclusions:

• The proposed seven-core fiber device functions as a compact and sensitive optical fiber curvature sensor.
• The sensor can be interrogated using either spectral shift or interference visibility.
• The device shows potential for various applications requiring precise curvature measurement.