Miniature optical spectrometers: Follow the money - Part II: The telecommunications boom

One of the most ubiquitous near-infrared (NIR) analyzers is not found in a chemical laboratory, a refinery, or next to a grain elevator; instead, it is found in doctors' offices, medical clinics, and emergency rooms. This is the pulse oximeter, a deceptively simple device that clips onto a finger to measure oxygen saturation in blood rapidly and non-invasively. It operates in the visible and shortwave NIR regions, employing discrete-wavelength semiconductor light sources: light emitting diodes (LEDs). It is, therefore, a good example of a dedicated function, miniature, NIR spectrometer, using modern photonics technology. Within a very short time after its introduction, the modern pulse oximeter completely displaced the previous instruments used to measure blood oxygen saturation, which were bulky, expensive, and sometimes painful for the patient. It can therefore be classified as a disruptive technology (1).