# Characteristics of the recommended fiber

The recommended fiber has the following characteristics:

Core diameter Cladding diameter | 62.5um 125um
Nominal Numerical Aperture | =0.275 +/- 0.015
Modal bandwidth (at 850nm) Attenuation (at 850nm) | 160 MHz.km (min) 3.75 dB/km (max)

If you are using 62.5/125um fiber to link your Ringnode to a concentrator, your maximum lobe-length is 2km.

If you have a large number of connections on your link, your losses could be much higher than those associated with the fiber that we recommend. Either measure or calculate the loss from the link to ensure that it meets the Optical Power Budget.