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overfilled launch (fiber optics) (OFL)

The light injection in optical waveguides is done with light emitting diodes and VCSEL lasers. The radiation area and the radiation angles of the two light sources mentioned are extremely different.

While light-emitting diodes have a relatively large emission area and a wide emission angle, the emission area of lasers is very small and the light emission is largely coherent.

As a result, light-emitting diodes are used with multimode fibers and over-radiate their core glass, which has a diameter of 50 µm and 62.5 µm. This over-radiation is known as overfilled launch (OFL) and results in a portion of the radiant energy not being used for signal transmission. This loss fraction is referred to as gap loss.

Overfilled Launch (above) and Underfilled Launch

Overfilled Launch (above) and Underfilled Launch

In general, it can be stated that surface-emitting LEDs overfire the core glass, whereas edge-emitting LEDs, lasers and VCSEL lasers have an extremely small radiation area and do not fully illuminate the core glass, which is referred to as underfilled launch (UFL).

Englisch: overfilled launch (fiber optics) - OFL
Updated at: 03.10.2018
#Words: 160
Links: light, vertical cavity surface emitting laser (fiber optics) (VCSEL), radiation (R), area, emission
Translations: DE

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