Asymmetric structure optical fiber humidity sensor assisted by the virtual Vernier effect

Area of Science:

• Optical Fiber Sensing
• Environmental Monitoring
• Nanomaterials

Background:

• Accurate relative humidity (RH) monitoring is crucial for various applications.
• Existing optical fiber sensors often face limitations in sensitivity and detection range.
• Developing novel sensing materials and structures is essential for enhanced RH measurement.

Purpose of the Study:

• To propose and demonstrate a novel asymmetric structure optical fiber sensor for relative humidity (RH) measurement.
• To investigate the use of polyvinyl alcohol (PVA) as a hygroscopic material for RH sensing.
• To enhance the sensitivity of the optical fiber sensor using a virtual Vernier effect.

Main Methods:

• Fabrication of an asymmetric fiber structure by splicing dispersion compensation fiber (DCF) and coreless fiber (NCF).
• Coating a polyvinyl alcohol (PVA) hygroscopic film on an etched section of the DCF.
• Applying fast Fourier transform (FFT) and inverse fast Fourier transform (IFFT) for signal processing and implementing a virtual Vernier effect.

Main Results:

• The sensor exhibited initial sensitivities of 0.1304 nm/RH% and 0.4452 nm/RH% in different RH ranges.
• The virtual Vernier effect significantly improved sensitivity to 2.869 nm/RH% (55%-75% RH) and 2.64 nm/RH% (75%-95% RH).
• The enhanced sensitivity represents a 22-fold and 6-fold increase, respectively, over the original measurements.

Conclusions:

• The proposed asymmetric optical fiber sensor with PVA coating offers a promising approach for RH monitoring.
• The implementation of a virtual Vernier effect effectively enhances the sensor's sensitivity.
• This advanced sensing technology holds potential for improved environmental and industrial humidity detection.