Nasal-cannula-integrated Fabry-Pérot fiber sensor for respiration-driven Morse code communication

Spontaneous breathing offers a viable non-limb-based interaction channel for patients with severe motor impairments. However, traditional electronic monitors are often limited by electromagnetic susceptibility and bulky designs. We report a flexible, wearable human-computer interface that incorporates a miniature Fabry-Pérot interferometer (FPI) fiber-optic sensor directly embedded within a standard nasal cannula. By measuring temperature-induced changes in cavity length, the sensor tracks exhaled airflow with high sensitivity. The sensor achieves an experimental temperature sensitivity of 0.23 V/^∘C with excellent linearity (R²=0.99), enabling robust discrimination of six distinct respiratory features. By mapping normal and rapid breathing to Morse code dots and dashes, the system decodes a complete alphanumeric dataset in real time. Subjects successfully demonstrated text input of emergency vocabulary, and this technology can further enable control of assistive functions such as smart home devices and emergency call systems.