Non-Adiabatically Tapered Optical Fiber Humidity Sensor with High Sensitivity and Temperature Compensation

Area of Science:

• Fiber optics
• Optical sensing
• Metrology

Background:

• Accurate simultaneous measurement of humidity and temperature is crucial for various applications.
• Existing sensors often suffer from crosstalk or require complex fabrication.
• Developing high-sensitivity, dual-parameter sensors remains an active research area.

Purpose of the Study:

• To demonstrate an all-fiber, high-sensitivity, dual-parameter sensor for simultaneous humidity and temperature measurement.
• To investigate the sensor's performance characteristics, including sensitivity, stability, and response time.
• To address the challenge of temperature-humidity crosstalk in optical sensing.

Main Methods:

• Fabrication of a symmetrical, non-adiabatic, tapered single-mode optical fiber.
• Operation near the dispersion turning point to induce mode coupling.
• Cascading a humidity-insensitive fiber Bragg grating (FBG) for temperature compensation.
• Utilizing the interference fringe in the transmission spectrum for humidity sensing.

Main Results:

• Achieved high humidity sensitivity of -286 pm/%RH without moisture-sensitive materials.
• Successfully compensated for temperature effects using a cascaded FBG for dual-parameter measurement.
• Demonstrated good humidity stability and a fast response time of 0.26 s.
• Observed interference fringes with uneven dips due to mode coupling at the dispersion turning point.

Conclusions:

• The developed all-fiber sensor offers a robust and sensitive solution for simultaneous humidity and temperature monitoring.
• The sensor's design effectively mitigates temperature-humidity crosstalk.
• Its performance characteristics indicate significant potential for applications like medical respiratory dynamic monitoring.