Chapter 5. Infrared Communication Basics

5.1. The Ir Spectrum

The infrared (Ir) part of the electromagnetic spectrum covers radiation having a wavelength in the range from roughly 0.78 μm to 1000 μm (1 mm). Infrared radiation takes over from extremely high frequency (EHF) at 300 GHz and extends to just below the red end of the visible light spectrum at around 0.76 μm wavelength. Unlike radio frequency radiation, which is transmitted from an antenna when excited by an oscillating electrical signal, infrared radiation is generated by the rotational and vibrational oscillations of molecules.

The infrared spectrum is usually divided into three regions, near, middle and far, where “near” means nearest to visible light (Table 5.1). Although all infrared ...

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