Vector bend sensor based on an integrated optical fiber coupler with Bragg gratings.

Area of Science:

• Optoelectronics
• Fiber Optics
• Sensor Technology

Background:

• Optical fiber sensors offer high sensitivity and immunity to electromagnetic interference.
• Accurate measurement of bending in optical fibers is crucial for various applications, including structural health monitoring and robotics.

Purpose of the Study:

• To demonstrate a novel vector bend sensor based on optical fiber.
• To achieve high sensitivity and accuracy in measuring both bend angle magnitude and direction.

Main Methods:

• Fabrication of a vector bend sensor using a single femtosecond laser writing step.
• Integration of Bragg gratings in each arm of a coupler within coreless silica optical fiber.
• Utilizing back-reflected Bragg wavelength and power level shifts for measurement.

Main Results:

• The sensor can resolve both bend angle magnitude and direction.
• Achieved peak wavelength sensitivity of up to 0.68 nm/° and peak power level sensitivity of up to 5.3 dB/°.
• Differential measurement using a dual grating approach mitigated lead-fiber losses, yielding up to 3.5 dB/° for peak power difference sensitivity.

Conclusions:

• The demonstrated vector bend sensor offers straightforward fabrication and compatibility with standard C-band wavelengths.
• The sensor shows high sensitivity and accuracy for vector bend measurement.
• This technology has potential applications in fields requiring precise fiber optic sensing.