Light emitting diodes are ideal for pulse oximeters as they :
Are cheap ( so can be used even in disposable probes)
Are very compact (can fit into very small probes)
Emit light in accurate wavelengths
Do not heat up much during use (low temperature makes it less likely to cause patient burns)
Light Emitting Diodes come in a variety of types that emit light in specific wavelengths. Fortunately, there are light emitting diodes (LED) that emit light in the red light and infrared light wavelengths and these are thus conveniently used in pulse oximeters. The exact wavelengths of the LEDs used depends on the manufacturer. For convenience, in our discussions, we made the red LED to have a wavelength of 650 nm and the infrared LED to have a wavelength of 950 nm (easy to remember). However, most text books will quote 660 nm and 940 nm.