# Modal bandwidth

Optical signals suffer some distortion as they pass along the fiber. Modal bandwidth is a measure of this distortion. For your network to operate correctly, the modal bandwidth of each fiber-optic link must be at least 80MHz. The longer a fiber-optic link, the lower its modal bandwidth.

You can estimate the modal bandwidth of a fiber-optic link by dividing the modal bandwidth of the fiber you are using, by the length of the fiber-optic link.

The fiber that we recommend has a modal bandwidth of 160MHz.km. The minimum modal bandwidth for each link is 80MHz. Therefore, the maximum length of link that you can use is 2km.

If you are using alternative fibers, you must still ensure that your links have a modal bandwidth of at least 80MHz. This may limit your maximum lobe length to less than 2km.