Optical sensors are typically interfaced with an optical unit. This optical component supplies the excitation light, which may be from a monochromatic source such as a diode laser or from a broadband source e.g. quartz-halogen that is filtered to provide a narrow bandwidth of excitation.
Typically, two wavelengths of light are employed: one that is sensitive to changes in the species to be measured and one that is unaffected by changes in the analyte concentration. This wavelength serves as a reference and is used to compensate for fluctuations in the source output and detector stability. The light output from the optic module is coupled into a fiber optic cable through the appropriate lenses and an optical connector.
Related: Optical Fiber Sensors and their Applications in Medical Field
In fluorescence-based sensors, the incident light excites fluorescence emission, which changes in intensity as a function of the concentration of the analyte to be measured. The emitted light travels back down the fiber to the monitor where the light is measured by a photodetector.
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[…] Biosensors can be divided into those that measure electrical properties e.g. pH meters, CO2 electrodes, O2 electrodes, field-effect transistor-based biosensors, etc. and those that measure optical properties like fiber-optic based biosensors. […]