Microsphere-Augmented PDMS integration in tapered FBG small-scale sensors for enhanced temperature sensitivity.

Area of Science:

• Optical Engineering
• Materials Science
• Sensor Technology

Background:

• Traditional fiber Bragg gratings (FBGs) have limitations in thermal sensitivity for certain applications.
• Improving strain transfer from the surrounding medium to the FBG is crucial for enhanced temperature sensing.
• Existing methods for enhancing FBG thermal sensitivity often involve trade-offs in sensor dimensions or complexity.

Purpose of the Study:

• To develop a novel high-sensitivity temperature sensor based on a tapered optical fiber with an integrated microsphere.
• To investigate the effect of tapered fiber waist diameter on sensor performance.
• To analyze the strain transfer mechanism between PDMS and the optical fiber for enhanced thermal response.

Main Methods:

• Fabrication of a fiber Bragg grating on a tapered optical fiber ending in a microsphere.
• Embedding the structure within a PDMS-filled silica capillary.
• Experimental analysis of sensor response across a temperature range (20°C–90°C) with varying taper waist diameters (60 μm to 20 μm).
• Validation using finite element analysis (FEA) simulations to correlate strain and sensitivity.

Main Results:

• Achieved a maximum wavelength temperature sensitivity of 221.2 pm °C⁻¹ for a 20 μm waist diameter, a 22-fold increase over a bare FBG.
• Demonstrated improved strain transfer due to the microsphere enhancing PDMS traction.
• FEA simulations confirmed the correlation between increased axial strain from PDMS and enhanced sensitivity.
• The sensor design showed improved performance in both dimensions and sensitivity compared to conventional methods.

Conclusions:

• The novel microsphere-integrated tapered FBG sensor offers significantly enhanced temperature sensitivity.
• The design effectively leverages improved strain transfer mechanisms for superior sensing performance.
• This approach presents a promising, compact, and highly sensitive solution for temperature monitoring applications.