Infrared emission from fluorescent lamps, in the wavelength region used by IRommunication devices, are due to high level atomic energy level transitions of either or both argon and mercury. For operating lamps argon emission is due mostly to the cathode fall electric field and is thus found mostly near the cathode. Mercury emission, and only the 1014 nm line is of significance, is distributed throughout the lamp discharge. Interference with communication devices in the infrared are normally due to the modulation of the IR emission, which becomes a problem when the lamp operating frequency or its first few harmonics are near the operating frequency of the communication device. It is shown that the modulation of the fluorescent lamp emission decreases with frequency and between 1 and 10 MHz largely disappear. This is attributed to the inability of the electron energy to change significantly at or above this frequency. Modulated emission from the cathode region of the lamp is the likely cause of interference in the 50 kHz to 1 MHz region.
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