Thermal blood flowmeter based on cascaded Fabry-Pérot Interferometers utilising the enhanced harmonic Vernier effect

Gong, Ruirong; Morgan, Stephen P.; Korposh, Serhiy; He, Chenyang; Hayes-Gill, Barrie R.; Correia, Ricardo

Abstract

Localised accurate blood flow measurement is crucial in various clinical scenarios for diagnosing and treating vascular conditions. An innovative thermal blood flowmeter that comprises cascaded Fabry-Pérot Interferometer (CFPI) and a multimode fibre (MMF) is presented. The MMF is connected to a green LED for modulating fluid temperature, and the resulting temperature change is inversely proportional to the flow rate. The CFPI consists of a polymer and air cavities of lengths 285.1 μm and 408.4 μm, respectively. The CFPI temperature sensitivity is enhanced due to the high thermo-expansion of the polymer compared to silica fibre. The typical discrete FPI system based on the Vernier effect comprises one sensing cavity and a reference cavity of constant length. In contrast, the CFPI is more compact and further enhances the sensor's sensitivity because the lengths of the two cavities change in opposite directions. The CFPI's temperature sensitivity is improved 117.4 times compared to a single polymer cavity and can reach 26.67±1.07 nm/ °C. Flow in a phantom system can be measured over a range from 20 ml/min to 300 ml/min.

Citation

Gong, R., Morgan, S. P., Korposh, S., He, C., Hayes-Gill, B. R., & Correia, R. (2025). Thermal blood flowmeter based on cascaded Fabry-Pérot Interferometers utilising the enhanced harmonic Vernier effect. Optics and Lasers in Engineering, 194, Article 109145. https://doi.org/10.1016/j.optlaseng.2025.109145

• Journal Article Type: Article
• Acceptance Date: Jun 3, 2025
• Online Publication Date: Jun 13, 2025
• Publication Date: Nov 1, 2025
• Deposit Date: Jun 16, 2025
• Publicly Available Date: Jun 17, 2025
• Journal: Optics and Lasers in Engineering
• Print ISSN: 0143-8166
• Electronic ISSN: 1873-0302
• Publisher: Elsevier
• Peer Reviewed: Peer Reviewed
• Volume: 194
• Article Number: 109145
• DOI: https://doi.org/10.1016/j.optlaseng.2025.109145
• Keywords: Optical fibre sensor; Fabry-Pérot Interferometers; Vernier effect; Temperature sensing; Blood flowmeter
• Public URL: https://nottingham-repository.worktribe.com/output/50437320
• Publisher URL: https://www.sciencedirect.com/science/article/pii/S0143816625003306?via%3Dihub
• Additional Information: This article is maintained by: Elsevier; Article Title: Thermal blood flowmeter based on cascaded Fabry-Pérot Interferometers utilising the enhanced harmonic Vernier effect; Journal Title: Optics and Lasers in Engineering; CrossRef DOI link to publisher maintained version: https://doi.org/10.1016/j.optlaseng.2025.109145; Content Type: article; Copyright: © 2025 The Authors. Published by Elsevier Ltd.