The correct answer is C. dB/km.
Attenuation is the loss of power in a signal as it travels through a medium. In optical fibers, attenuation is caused by scattering and absorption of light. Scattering is the redirection of light by particles in the fiber, while absorption is the conversion of light energy into heat.
The unit of measurement of attenuation is decibels per kilometer (dB/km). This unit is used because attenuation is typically very small, and it is convenient to express it in a logarithmic scale. Attenuation is usually measured at a specific wavelength of light, and it can vary depending on the type of fiber, the length of the fiber, and the environmental conditions.
Option A, km, is not the unit of measurement of attenuation. Attenuation is a measure of power loss, not distance.
Option B, dB, is a unit of measurement of power. However, it is not the unit of measurement of attenuation. Attenuation is typically measured in dB/km.
Option D, Coulomb’s, is a unit of measurement of electric charge. It is not the unit of measurement of attenuation.