Quasi-distributed fiber sensitization sensing technique based on FMCW interferometry and the virtual Vernier effect

Area of Science:

• Photonics and Optical Sensing
• Environmental Monitoring
• Interferometry

Background:

• Traditional fiber-optic sensors often lack the sensitivity and spatial resolution required for detailed environmental monitoring.
• The Vernier effect offers a method for signal amplification in optical sensing systems.
• Frequency-modulated continuous-wave (FMCW) interferometry provides precise measurement capabilities.

Purpose of the Study:

• To propose and demonstrate a quasi-distributed fiber-optic sensing technique for enhanced seawater salinity detection.
• To integrate frequency-modulated continuous-wave (FMCW) interferometry with the Vernier effect for amplified sensing.
• To achieve high spatial resolution and multipoint salinity measurements using Fabry-Perot (FP) microcavities.

Main Methods:

• Fabrication of an open-cavity Fabry-Perot sensor (FP-Sen) for seawater salinity detection.
• Implementation of FMCW interferometry with digital signal processing (DSP) for precise localization and demodulation of multiple FP-Sens.
• Construction of a virtual interferometric spectrum (VIS) to generate an optical Vernier effect for amplified salinity readings.

Main Results:

• Demonstrated a quasi-distributed FMCW system with three cascaded FP-Sens for multipoint salinity sensing.
• Achieved a sensitivity of 2.235 nm/‰ within the 25-30‰ salinity range, a 9-times enhancement over single sensors.
• Verified good sensor stability through experimental analysis and highlighted the technique's advantages for numerous sensing points.

Conclusions:

• The proposed quasi-distributed fiber-optic sensing technique effectively enhances salinity detection sensitivity using the Vernier effect and FMCW interferometry.
• The system allows for high spatial resolution and multipoint measurements, making it suitable for large-scale environmental monitoring.
• This approach presents a promising solution for practical applications demanding numerous sensitized sensing points.