Optics 101

An Introduction to Attenuation

Attenuation is defined as the gradual loss in the intensity of any kind of flux when it passes through a medium.

An Introduction to Attenuation 

The most common example of an attenuator is when water, light or sound waves under go a loss of intensity when they pass through water. During earthquakes, the intensity of a seismic wave is attenuated by the ground as it travels away from the epicenter.

Some of the useful applications areas of attenuation effects include optical fiber communications and radio wave communications. 

In chemical spectroscopy, attenuation calculations are carried out using the Beer-Lambert Law. According to this law, attenuation is an exponential function of the path length through the medium.

In an engineering context, attenuation is measured in decibels per unit length of medium and represented as the attenuation co-efficient of the medium.

Optical Attenuators

Attenuators are used in fiber optic communications to test power levels or for matching the transmitter and receiver signals. An optical attenuator is used to reduce the level of a signal present in free space or in an optic cable.

There are three basic types of attenuators:

  • fixed
  • step-wise
  • continuously variable

Attenuation Correction in Medical Imaging

In medical imaging, attenuation occurs when the signals are absorbed by the body. Attenuation of photons during medical imaging leads to image distortion and increase in noise.

In order to achieve error-free imaging suitable attenuation correction mechanisms need to be included in medical imaging devices such as PET and CT scan.

References and Further Reading


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