The characteristics of light are summarized in the following. The first three parameters scalar characteristics of light wheras the last parameter, polarization, describes the vector nature of light.

The choice of wavelength depends upon the loss profile of the medium. For optical fiber the wavelength has to be 1300nm or 1550nm for low loss.

The spectral width has direct bearing on the data rate which the medium can support. Larger the spectral width, smaller is the data rate. A semiconductor laser typically has spectral width about 20 to 100 times less compared to LED. Consequently, laser based communication can support much higher data rates.