# Labelling your fiber-optic cable

| The connectors on your Ringnode are protected by dust caps. Be careful not to touch the ends of these connectors. If you scratch the connectors, or get any dirt or grease on them, you will severely degrade the performance of the Ringnode.

If your cable is not labelled in a way that makes the Rx and the Tx connectors distinguishable, perform the following steps:

1. Take either end of your cable and label one connector R, and the other, T.

2. Hold connector R to a bright light (and shield connector T with your hand). When you look at the connectors at the other end of the cable, you should see a tiny circle of light at one of them. (Look at it end-on. You may need to look closely.)

3. Label the connector that is emitting light, T. Label the other connector at that end, R.

4. Take either end of your fiber-optic cable and attach connector R to the Rx connector and connector T to the Tx connector, on your Ringnode.

5. Take the other end of your cable and attach connector R to an Rx connector, and connector T to the corresponding Tx connector, on your concentrator.