Editing Rayleigh scattering (section)

==In amorphous solids – glasses – optical fibers==
Rayleigh scattering is an important component of the scattering of optical signals in [[optical fibers]]. Silica fibers are glasses,  disordered materials with microscopic variations of density and refractive index. These give rise to energy losses due to the scattered light, with the following coefficient:<ref>Rajagopal, K. (2008) ''Textbook on Engineering Physics'', PHI, New Delhi, part I, Ch. 3, {{ISBN|8120336658}}</ref>
<math display="block">\alpha_\text{scat} = \frac{8 \pi^3}{3 \lambda^4} n^8 p^2 k T_\text{f} \beta</math>

where ''n'' is the refraction index, ''p'' is the photoelastic coefficient of the glass, ''k'' is the [[Boltzmann constant]], and ''β'' is the isothermal compressibility. ''T''<sub>f</sub> is a ''fictive temperature'', representing the temperature at which the density fluctuations are "frozen" in the material.