Software-Defined Optical Coherence Measurement of Seawater Refractive Index Variations
The seawater refractive index is an important parameter in marine environments, with its variations depending on the specific environmental conditions. During practical applications, modulation parameters such as the sampling rate, bandwidth, and filters directly affect the signal-to-noise ratio (SN...
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2025-05-01
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| author | Jiaxin Zhao Xinyi Zhang Qi Wang Liyan Li Songtao Fan Yongjie Wang Yan Zhou |
| author_facet | Jiaxin Zhao Xinyi Zhang Qi Wang Liyan Li Songtao Fan Yongjie Wang Yan Zhou |
| author_sort | Jiaxin Zhao |
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| description | The seawater refractive index is an important parameter in marine environments, with its variations depending on the specific environmental conditions. During practical applications, modulation parameters such as the sampling rate, bandwidth, and filters directly affect the signal-to-noise ratio (SNR) and need to be adjusted in real-time according to the characteristics of the target signal. Low-cost software-defined radio (SDR) offers significant advantages in this regard. This paper proposes an optical coherence measurement method for seawater refractive index changes based on orthogonal demodulation using SDR along with simulation calculations, and the results demonstrate that the resolution of the refractive index change rate is <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>3.165</mn><mo>×</mo><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>9</mn></mrow></msup></mrow></semantics></math></inline-formula> RIU/s, corresponding to a refractive index change resolution of <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>10</mn></mrow></msup></mrow></semantics></math></inline-formula> RIU (frequency range 1 Hz–100 Hz, measurement range 0.1 m). By adopting SDR as the implementation platform for the demodulation algorithm and using a radio-frequency source to simulate interference signals for demodulating the refractive index variation, the results show that the relative error of the SDR demodulation results is below 0.3%. Additionally, this study developed a software-defined optical coherence measurement system for the seawater refractive index and measured the refractive index changes in deionized water during heating. The experimental results showed that the root mean square error (RMSE) of the refractive index changes obtained through SDR demodulation was <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>5.68</mn><mo>×</mo><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>6</mn></mrow></msup></mrow></semantics></math></inline-formula> RIU. This research provides a novel demodulation method for high-precision measurements of seawater refractive index changes under different marine environments. |
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| spelling | doaj-art-6b87c6f63d2f436ab9b2a8a493f1780c2025-08-20T02:33:58ZengMDPI AGSensors1424-82202025-05-012510311910.3390/s25103119Software-Defined Optical Coherence Measurement of Seawater Refractive Index VariationsJiaxin Zhao0Xinyi Zhang1Qi Wang2Liyan Li3Songtao Fan4Yongjie Wang5Yan Zhou6Optoelectronic Systems Laboratory, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, ChinaOptoelectronic Systems Laboratory, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, ChinaOptoelectronic Systems Laboratory, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, ChinaOptoelectronic Systems Laboratory, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, ChinaOptoelectronic Systems Laboratory, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, ChinaOptoelectronic Systems Laboratory, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, ChinaOptoelectronic Systems Laboratory, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, ChinaThe seawater refractive index is an important parameter in marine environments, with its variations depending on the specific environmental conditions. During practical applications, modulation parameters such as the sampling rate, bandwidth, and filters directly affect the signal-to-noise ratio (SNR) and need to be adjusted in real-time according to the characteristics of the target signal. Low-cost software-defined radio (SDR) offers significant advantages in this regard. This paper proposes an optical coherence measurement method for seawater refractive index changes based on orthogonal demodulation using SDR along with simulation calculations, and the results demonstrate that the resolution of the refractive index change rate is <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>3.165</mn><mo>×</mo><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>9</mn></mrow></msup></mrow></semantics></math></inline-formula> RIU/s, corresponding to a refractive index change resolution of <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>10</mn></mrow></msup></mrow></semantics></math></inline-formula> RIU (frequency range 1 Hz–100 Hz, measurement range 0.1 m). By adopting SDR as the implementation platform for the demodulation algorithm and using a radio-frequency source to simulate interference signals for demodulating the refractive index variation, the results show that the relative error of the SDR demodulation results is below 0.3%. Additionally, this study developed a software-defined optical coherence measurement system for the seawater refractive index and measured the refractive index changes in deionized water during heating. The experimental results showed that the root mean square error (RMSE) of the refractive index changes obtained through SDR demodulation was <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>5.68</mn><mo>×</mo><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>6</mn></mrow></msup></mrow></semantics></math></inline-formula> RIU. This research provides a novel demodulation method for high-precision measurements of seawater refractive index changes under different marine environments.https://www.mdpi.com/1424-8220/25/10/3119software-defined radiorefractive index changesignal demodulationinterferometry |
| spellingShingle | Jiaxin Zhao Xinyi Zhang Qi Wang Liyan Li Songtao Fan Yongjie Wang Yan Zhou Software-Defined Optical Coherence Measurement of Seawater Refractive Index Variations Sensors software-defined radio refractive index change signal demodulation interferometry |
| title | Software-Defined Optical Coherence Measurement of Seawater Refractive Index Variations |
| title_full | Software-Defined Optical Coherence Measurement of Seawater Refractive Index Variations |
| title_fullStr | Software-Defined Optical Coherence Measurement of Seawater Refractive Index Variations |
| title_full_unstemmed | Software-Defined Optical Coherence Measurement of Seawater Refractive Index Variations |
| title_short | Software-Defined Optical Coherence Measurement of Seawater Refractive Index Variations |
| title_sort | software defined optical coherence measurement of seawater refractive index variations |
| topic | software-defined radio refractive index change signal demodulation interferometry |
| url | https://www.mdpi.com/1424-8220/25/10/3119 |
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