Absorption

The loss of power (signal) in an optical fiber resulting from conversion of optical power (specific wavelengths of light energy into heat.Caused principally by impurities,such as water, ions of copper or chromium (transition metals), and hydroxyl ions, and by exposure to nuclear radiation. Expressed in dB/km (decibels per kilometer).Absorption and scattering are the main causes of attenuation(loss of signal) of an optical waveguide during transmission through optical fiber.