Ultrasensitive fiber-optic Vernier salinometer based on an integrated dual-microcavity interferometer

Yue Yu , Chuanxu Liu , Liangtao Hou

Optics Letters +

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June 13, 2025

View abstract on PubMed

Summary

We developed a novel optical fiber sensor for highly sensitive seawater salinity measurement. This sensor achieves a resolution of 0.0032‰, offering a promising tool for marine monitoring.

Area Of Science

Photonics and Sensor Technology
Marine Science Instrumentation
Optical Fiber Sensing

Background

Accurate salinity measurement is crucial for understanding oceanographic processes and climate change.
Existing methods for salinity detection can be complex or lack the required sensitivity.
Integrated optical fiber sensors offer potential for compact, high-performance sensing solutions.

Purpose Of The Study

To report a novel integrated optical fiber Vernier sensor for ultra-sensitive salinity measurement.
To demonstrate the sensor's performance characteristics, including sensitivity, resolution, and temperature cross-sensitivity.
To highlight the sensor's potential for practical marine environment monitoring.

Main Methods

Fabrication of a no-core-hollow-core-no-core (NCF-HCF-NCF) fiber structure within a millimeter-length open-cavity.
Utilizing the Vernier effect by precisely adjusting optical path differences for enhanced sensitivity.
Systematic experimental testing to evaluate salinity and temperature responses.

Main Results

Achieved a high magnification factor of 8.33.
Demonstrated a salinity sensitivity of 18.43 nm/‰, with a resolution of 0.0032‰.
Observed a temperature sensitivity of -10.25 nm/℃, with measurement errors constrained to 1.9%.

Conclusions

The proposed integrated optical fiber Vernier sensor enables ultra-sensitive salinity measurements.
The sensor exhibits high resolution, good accuracy, and simple fabrication.
This cost-effective sensor is highly promising for high-accuracy marine environment monitoring.