# The optical-power budget

| Do not use fiber cable with a light loss that exceeds 3.75dB/Km with Madge Ringnodes.

The optical-power budget is the sum of the losses of light that occur over a particular fiber-optic link. Some light is always lost during communication over fiber-optic cable. It is lost both along the cable itself, and at each connection on the link.

The draft standard allows for a signal loss of 13dB from the link between your Ringnode and a concentrator. Each connection on your link typically entails a loss of 1dB, and you need to anticipate a further loss of 3dB to allow for the effects of temperature, wear to your connector, possible splices of broken cable, and other future causes of light-loss.

If you are using alternative fiber, or you have a large number of connections on your link, your losses could be much higher than those associated with the fiber we recommend. Either measure or calculate the loss from the link to ensure that it does not exceed 13dB.