L-band is a name used for a fixed range of infrared frequencies. The definition of the range depends on the application, with different bands used for fibre-optic communications and astronomy.
Fibre-optic telecommunications
In infrared optical communications, L-band refers to the wavelength range 1565–1625 nm. Optical Fiber Communications article in rp-photonics' Encyclopedia of Laser Physics and Technology (accessed Nov. 11 2010) The L-band is located next to the conventional (C) band (1530–1565 nm).
Infrared astronomy
In infrared astronomy, the L band is an atmospheric transmission window centred on 3.5 micrometres (in the mid-infrared).
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