Breathing Monitor Using Dye-Doped Optical Fiber

Abstract

Amorphous silica aerogels doped with Al 3+ ions (SADAs) were prepared by the sol-gel route and supercritical drying. The visible luminescence of SADAs was measured and compared with that of porous silicon (PS), pure silica aerogels (PSAs) and silica xerogels doped with Al 3+ ions (SXDAs). The effect of annealing on the luminescence intensity of SADAs was investigated. Results show that (1) the luminescent intensity of as-prepared SADAs is much higher than that of as-prepared PSAs and SXDAs after annealing at 300 • C; (2) after annealing at 500 • C, the visible luminescence of SADAs is further substantially enhanced and becomes much higher than that of PS. However, for PSAs and SXDAs after annealing at 500 • C the luminescent intensity is still kept at a very low value in comparison with that of SADAs. The strong visible luminescence appearing in SADAs is ascribed to significant amounts of the twofold coordinated Si (the Si(II) 0 (neutral) centre) in SADAs.

Biomedical sensors using optical fibres

“…Since the water vapour in human respiration exceeds that in the room, the patient's expiration produces a fluorescent signal which is detected by an electro-optical unit at the nurses' station. This kind of monitoring is particularly useful in detecting abnormal breathing in bedridden patients [21].…”