In this and the following posts we will take in some details about attenuation, we will cover the topics mentioned in the last post.

1- Fiber Spectral Attenuation:
the two main loss mechanisms in fiber is absorption and scattering,

1-1-Light absorption:

As light passes through fiber it is absorbed and converted into heat, due to molecular resonance, for example hydrogen and hydroxide resonance occurs at 1244 nm and 1383 nm.

1-2-Rayleigh scattering:


Scattering causes the dispersion of light energy in all directions, and one of the directions is the backward direction in this case the scattering is called "backscattering".
Forward light scattering (Raman scattering) and backward light scattering (Brillouin scattering) are two additional types of scattering those can occur under high power conditions.
Attenuation depends on the fiber type and the wavelength, Rayleigh scattering as an example is inversely proportional to the 4th power of the wavelength, in the following graph you will find the attenuation of a light signal in a fiber medium is plotted against the wavelength of that signal.