Definition of attenuation in The Network Encyclopedia.

What is Attenuation (in computer networking)?

The loss of signal strength with long distances when signals travel along cabling. Attenuation values for actual cables are measured in units of decibels (dB) - a standard measurement value used in communication for expressing the ratio of two values of voltage, power, or some other signal-related quantity.

For example, a drop of 3 dB corresponds to a decrease in signal strength of 50 percent or 2:1, while a drop of 6 dB corresponds to a decrease of 75 percent or 4:1. Attenuation values for cabling media are expressed in units of decibels per 1000 feet, which express the amount of attenuation in decibels for a standard 1000-foot length of cabling composed of that media.

Copper cabling has much greater attenuation than fiber-optic cabling; therefore, copper is suitable only for relatively short cable runs. Typical attenuation values for copper category 5 cabling vary with frequency and are shown in the table that follows. Attenuation for lower-grade cable is slightly higher.

Attenuation Values for Copper Category 5 Cabling

Signal Frequency Attenuation
4 MHz
13 dB/1000 feet
10 MHz
20 dB/1000 feet
20 MHz
28 dB/1000 feet
100 MHz
67 dB/1000 feet

Attenuation by signal absortion

Attenuation is caused by signal absorption, connector loss, and coupling loss. To minimize attenuation, use high-grade cabling such as enhanced category 5 cabling. Also try to minimize the number of connector devices or couplers, ensuring that these are high-grade components as well. When a signal attenuates a large amount, the receiving device might not be able to detect it or might misinterpret it, therefore causing errors.