Figure 7 gives an overview of the calculation of the optical power of 100 LEDs in comparison to
the sun for a typical application scenario. In this example the ratio between sun and active light is
18,000 =85db at a distance of 40 m (20 ° viewing angle). In the following section we will show how
this ratio can be improved by intelligent system design. Firstly, the optical input signal is
spectrally filtered. Although LEDs in the near infrared have a typical spectral width of 50 nm,
thermal drift of LEDs and auto motive temperature range requirements must also be taken in to
account. These facts allow only a medium spectral filter width of approximately 100nm to be used .