A Refractive Index Sensor Based on Spectral Interrogation of a Long Tapered Side-Hole Optical Fiber

Area of Science:

• Photonics and Sensing Technology
• Optical Fiber Sensors
• Refractive Index Measurement

Background:

• Refractive index (RI) sensing is crucial in various scientific and industrial fields.
• Existing RI sensing methods often involve complex configurations like interferometric or plasmonic sensors.
• There is a need for simpler, yet sensitive, RI sensing technologies.

Purpose of the Study:

• To develop and characterize an external refractive index (RI) sensor.
• To investigate the spectral transmission characteristics of a long tapered side-hole optical fiber (S-H OF).
• To evaluate the sensitivity of the S-H OF sensor to external RI variations.

Main Methods:

• Fabrication of a long tapered side-hole optical fiber (S-H OF) sensor.
• Fusion splicing the S-H OF with standard single-mode fibers (SMFs).
• Spectral analysis of light transmission using a supercontinuum source and optical spectrum analyzer (OSA).
• Testing with immersion liquids of varying refractive indices (1.32-1.42).
• Power loss measurements across different wavelength ranges (600-1800 nm).

Main Results:

• The sensor demonstrated sensitivity to external RI changes.
• The highest sensitivity achieved was 622 ± 11 nm/RIU in the near-infrared region.
• Spectral characteristics of the S-H OF were significantly affected by the surrounding RI.

Conclusions:

• Long tapered S-H OFs are suitable for spectral-interrogation-based RI sensing.
• The developed sensor provides a promising and simpler alternative to complex existing RI sensing technologies.
• This technology holds potential for various applications requiring precise RI monitoring.