Optical aspects of a fibre-optic sensor for respiratory rate monitoring.

A new sensor for respiratory rate monitoring is described. The sensor uses an optical fibre that detects the evaporated humidity from the mouth and/or nose at each exhalation. The condensed humidity substantially alters the coupling of light from the optical fibre to the surrounding medium, which can be monitored by a photo-detector. The sensing principle is evaluated using ray-tracing simulation and scattering measurements.