signal loss

Definition of signal loss in The Network Encyclopedia.

What is signal loss?

The loss of strength of a signal as it propagates over a medium. Generally, the term refers to loss of signal strength in guided media such as copper cabling and fiber-optic cabling. Unguided media such as wireless networking technologies have signals that decrease in power per unit area primarily because of the inverse square law.

How It Works

A number of mechanisms can cause signal loss in a wire or cable:

  • Attenuation:
    Caused by resistive losses in the cable and affects only copper cabling


  • Absorption:
    Causes signal loss in fiber cabling because the glass core material is not perfectly transparent


  • Fractures:
    Can result in both attenuation and absorption of signal strength


  • Splices, connectors, and couplings:
    Involve dissimilar materials joined together and generally produce some loss


Signal loss is generally expressed in units of decibels (dB) per source of the loss. The following table shows typical signal loss values for fiber-optic cabling. These rough values are useful for estimating total signal loss, which you calculate by simply adding the loss for each element in the light path.

Signal Loss Values for Fiber-Optic Cabling

Source of Loss Approximate Signal Loss
Connector loss
3 dB/termination
Coupling loss
2 dB/coupler
Intrinsic loss
6 dB/1000 meters
Microbending loss
Increases with decreasing bend radius
Splice loss
4 dB/splice


The total end-to-end signal loss of a light path through a fiber-optic cabling system is known as the optical power budget. If this value is greater than the power launch rating of your line driver, your system won’t work.