If you're wondering how hot a filament needs to get to produce light, color temperature is based on the relationship between temperature and radiation emitted by a hypothetical black body radiator.

As the temperature of this body is lowered, molecular activity diminishes. When all activity stops, the temperature of this theoretical object is " absolute zero" or 0 degrees Kelvin (° K), which is also equal to -273° Centigrade.

As it relates to fiber optic light sources, most lamps contain tungsten filament in Quartz Halogen envelope. Because the tungsten behaves similar to the theoretical black body, as it heats up, it begins to produce light. When the filament reaches 2927°C,or 5300°F, or 3200°K we're in business!