Lateral Offset Single-Mode Fiber-Based Fabry-Perot Interferometers with Vernier Effect for Hydrogen Sensing

Area of Science:

• Photonics and Sensing Technologies
• Materials Science for Gas Detection
• Optical Fiber Instrumentation

Background:

• Hydrogen (H2) gas sensing is critical for safety and industrial monitoring.
• Existing optical fiber sensors often lack the required sensitivity and linear response.
• Fabry-Perot interferometers (FPIs) offer potential for enhanced sensing but require amplification mechanisms.

Purpose of the Study:

• To propose and demonstrate a high-sensitive optical fiber hydrogen sensor.
• To leverage the Vernier effect for amplified wavelength shift in response to H2 concentration.
• To achieve a linear and accurate measurement of H2 concentration.

Main Methods:

• Cascading three Fabry-Perot interferometers (FPIs) using a single-mode fiber with lateral offset welding.
• Coating polydimethylsiloxane (PDMS) to form the cascaded FPIs and generate a Vernier envelope spectrum.
• Applying a Pd/WO3 hydrogen-sensitive material to induce thermal expansion and refractive index changes in PDMS upon H2 exposure.

Main Results:

• The proposed sensor exhibits a linear measurement sensitivity of 6.214 nm/% in the 0-1% H2 concentration range.
• The Vernier effect amplifies sensitivity by 16.11 times compared to a single FPI.
• The sensor demonstrates high sensitivity, ease of preparation, compact structure, and suitability for long-distance transmission.

Conclusions:

• The cascaded FPI optical fiber sensor effectively utilizes the Vernier effect for highly sensitive H2 detection.
• The Pd/WO3 coating enables a reliable sensing mechanism based on H2-induced thermal expansion.
• This sensor design offers a promising solution for accurate and efficient hydrogen monitoring applications.