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Proper Techniques for Fiber Optic Loss Testing

Fiber Loss Testing

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There are two methods to measure test loss, single-ended loss and double-ended loss. Single-ended loss works by using only the launch cable while the double-ended loss works using a received cable attached to the meter also.

Before You Test Unknown Cables:
Use the single-ended method to test all your reference cables before you start testing. Don’t use any cables for reference if their loss is too high (> 0.5 dB).

Remember that the launch power reference is set the same way for all measurements, minimizing confusion!

· Guidelines for what loss you should receive when testing cables, for each connector, figure 0.5 dB loss and for each slice, figure 0.2dB loss.

Single-Ended Loss
First, mate the cable you want to test to the reference launch cable and measure the power out the far end with your power meter. You are measuring the loss of the connector mated to the launch cable and the loss of any fiber, splices or other connectors in the cable you are testing. By reversing the cable to test the connector on the other end, you can isolate a bad connector.

Double-Ended Loss Tests
Start with attaching the cable to the test between two reference cables, one attached to the source and one to the meter. Here, you are measuring two connectors’ loses, one on each end, plus the loss of all the cable or cable in between.

By connecting the light source and a power meter directly to the link you are measuring without a patch cord, you are not making a fiber connector to fiber connector junction. Therefore, the proper way to do the fiber loss test is to connect the patch cord to the power meter and connect a second patch cord to the light source, with a connector sleeve to connect the two patch cords.

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