Polarization maintaining fiber π phase shift grating based temperature-salinity-depth sensing system and demodulation method

By coating a salinity-sensitive thin film onto the π-phase shift region of a polarization-maintaining fiber π-phase shift grating and combining it with the sensitivity matrix demodulation method, a high-precision synchronous measurement of multiple parameters of an ocean temperature, salinity, and depth sensor was achieved. This solved the problems of complex structure and cross-sensitivity in existing technologies, and enabled the miniaturization and high reliability of the sensor.

CN122408844APending Publication Date: 2026-07-17NAT UNIV OF DEFENSE TECH
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Patent Information

Authority / Receiving Office
CN · China
Patent Type
Applications(China)
Current Assignee / Owner
NAT UNIV OF DEFENSE TECH
Filing Date
2026-05-22
Publication Date
2026-07-17

AI Technical Summary

Technical Problem

Existing fiber optic sensors suffer from cross-sensitivity issues in ocean temperature, salinity, and depth measurements, making it difficult to achieve high-precision simultaneous measurement of multiple parameters. Furthermore, their complex structure and high cost make it difficult to achieve true single-point multi-parameter synchronous sensing.

Method used

A temperature, salinity, and depth sensing system based on a polarization-maintaining fiber π-phase-shift grating is adopted. By locally coating a salinity-sensitive film in the π-phase-shift region, the characteristic wavelength changes of the fast and slow axis reflection center wavelength and the transmission window wavelength are utilized, combined with a sensitivity matrix, to achieve synchronous decoupled measurement of temperature, salinity, and depth.

Benefits of technology

It achieves high-precision synchronous decoupled measurement of temperature, salinity, and depth. The sensor structure is highly integrated and miniaturized, which reduces manufacturing costs, improves mechanical reliability and measurement accuracy, and avoids cross-sensitivity interference.

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Abstract

This invention relates to the field of marine environmental monitoring technology, and discloses a temperature, salinity, and depth sensing system and demodulation method based on a polarization-maintaining fiber optic π-phase-shifting grating. The system includes a polarization-maintaining fiber and a π-phase-shifting fiber grating, with the π-phase-shifting fiber grating inscribed on the polarization-maintaining fiber and serving as a single sensing unit. The reflection spectrum of the sensing unit contains reflection peaks along both the fast and slow axes, with an ultra-narrow linewidth transmission window introduced by the π-phase shift at the center of each peak. A salinity-sensitive thin film is coated on the π-phase-shifting region of the sensing unit, covering the π-phase-shifting region and extending into a local area of ​​the π-phase-shifting fiber grating, but not covering the entire grating. By locally coating the salinity-sensitive thin film on the π-phase-shifting region of a single polarization-maintaining fiber optic π-phase-shifting grating, and simultaneously extracting the characteristic wavelength changes of its fast and slow axis reflection center wavelengths and transmission window wavelengths, a sensitivity matrix is ​​used to achieve synchronous decoupled measurement of the three parameters of temperature, salinity, and depth.
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