Tapered plastic fiber optic sensor for cuffless continuous blood pressure monitoring (1 citation).
The tapered plastic optical fiber acts as an intensity modulator. Arterial pulsation applies mechanical pressure to the waist, altering light transmission. The photodetector maps the intensity waveform to blood pressure via Pulse Transit Time (PTT).
Hypertension affects over 1.3 billion people worldwide, yet the standard method for blood pressure measurement — the inflatable arm cuff — remains uncomfortable, inconvenient for continuous monitoring, and impractical for wearable health devices. Most patients only get spot measurements during clinic visits, missing the critical diurnal variations that inform treatment.
Optical solutions based on photoplethysmography (PPG) have emerged, but most face challenges with motion artifacts, skin tone dependence, and the need for complex multi-wavelength calibration. There was a clear need for an alternative transduction mechanism that is sensitive, mechanically simple, and immune to electromagnetic interference.
Plastic optical fibers offer exactly those properties: they are flexible, biocompatible, and can transduce mechanical pressure directly into optical intensity modulation. A tapered fiber geometry amplifies sensitivity at the sensing region while maintaining robust light transmission.
The Plastic Fiber Optic Sensor (PFOS) system uses a tapered plastic optical fiber with a narrowed waist region as the sensing element. An infrared LED (940 nm) injects light into the fiber, which travels via total internal reflection through the core. When mechanical pressure from an arterial pulse is applied to the tapered waist, micro-bending losses cause a portion of the light to escape, modulating the transmitted intensity at the photodetector.
Sigit was part of the research team that tested four PFOS configurations — Bend, Bend with 1 scratch, Bend with 3 scratches, and Straight with 3 scratches — evaluating each for sensitivity and linearity. The sensor was placed on the wrist over the radial artery, and the Pulse Transit Time (PTT) method was used to derive systolic and diastolic pressure values from the optical waveform.
The Bend configuration (simple bending of the tapered waist without surface modifications) provided the best balance of sensitivity (0.27%/mmHg) and linearity (R² = 0.96), making it the recommended configuration for most applications.
The Bend configuration shows quasi-linear intensity response to applied pressure across the physiological range (80–140 mmHg). Higher pressure increases micro-bending at the taper, reducing transmitted light. Sensitivity: 0.27% intensity drop per mmHg.
Bend gives the best balance of sensitivity and linearity. Adding scratches increases sensitivity but degrades linearity — useful for low-pressure applications where maximum signal change is needed.
Systolic readings show mean absolute error (MAE) of 3.4 mmHg and diastolic MAE of 2.1 mmHg against the cuff sphygmomanometer reference across 12 subjects. The PFOS readings are within ±5 mmHg of the reference in 92% of measurements, meeting AAMI SP10 standards for non-invasive blood pressure devices.
The PFOS achieved mean absolute errors of 3.4 mmHg for systolic and 2.1 mmHg for diastolic measurements across 12 subjects. Overall correlation with the cuff sphygmomanometer reached R = 0.94, and 92% of readings fell within ±5 mmHg of the reference — meeting the AAMI SP10:2002 standard for non-invasive blood pressure device accuracy.
The Pulse Transit Time approach proved effective at separating systolic and diastolic phases from the optical waveform. Sensor placement on the wrist showed good signal-to-noise ratio without the need for additional skin preparation or coupling gel. The system demonstrates feasibility for integration into a wearable wristband device for continuous, cuffless blood pressure monitoring.
Indonesian Physical Review, Vol. 8 No. 1, 2025
DOI: 10.29303/ipr.v8i1.395
Shares the same instrumentation and sensor design philosophy — low-cost optical sensing applied to biological/environmental monitoring.
Health monitoring theme — the fiber optic BP sensor could feed physiological data into a broader crisis monitoring dashboard.
This work extends Sigit's instrumentation expertise into biomedical sensing, applying optical fiber technology to non-invasive physiological monitoring. The tapered PFOS design builds on principles shared with his other sensor-based projects in environmental and biological measurement.