Respiration rhythm monitoring in sleep based on weight movement using hetero-core fiber optic sensors

This paper describes respiration monitoring during sleep using hetero-core fiber optic pressure sensors. The hetero-core fiber optic sensor has high sensitivity to macro-bending action as a result of the core diameter difference corresponding to the sensor portion due to stable single-mode transmission. Pressure sensors employing hetero-core fiber optics were fabricated to have a wide sensitivity to small pressure changes resulting from minute body motions such as respiration in sleep and large pressure changes such as a roll-over action. The fabricated pressure sensors were installed in a conventional bed. The pressure characteristic performance of all the fabricated pressure sensors was found to show a monotonic response in the optical loss change with weight changes. The sensitivities of the hetero-core pressure sensors for a weight change of 3.0 kg were in the range of 0.55-1.80 dB. Additionally, even in the case of different body postures such as lying on one's side, a slight body movement due to respiration could be detected by the hetero-core pressure sensors.