Pulse Wave Velocity Measurement With Multiplexed Fiber Optic Fabry–Perot Interferometric Sensors

The paper presents an approach to noninvasively measure pulse wave delay and velocity by means of two multiplexed fiber-optic Fabry-Perot interferometric sensors interrogated by means of spectral interferometry. The pulse wave signals were measured with 1 kHz sampling rate. The obtained optical path difference resolutions are on the order of tens picometers, which allowed the pulse wave signal features as small as 100 pm to be clearly observed in the demodulated waveforms. The pulse wave velocity between different arteries was measured, demonstrating good agreement with the known data, where applicable. The paper also presents a mathematical model based on Cramer-Rao approach, describing the fundamental resolution limits of the pulse wave delay measurement. The derived mathematical model is not limited to fiber-optic pulse wave sensors and can be used for estimating the performance of other systems, such as photoplethysmographic and ultrasound. The reported work paves the way to development of novel all-optical non-invasive systems for medical diagnostics and vital signs monitoring, including portable devices.