Look before you test
A fibre link fails its test. The installer tests it again and it fails again. Then someone looks at the connector end through an inspection viewer and sees a thick smear of dust.
One wipe and the link passes. Many fibre test failures are dirt. That is why good testers inspect first.
Key words
| Word | What it means |
|---|---|
| Inspection | looking at a connector end through a viewer to check it is clean |
| Tier 1 | the basic fibre test of loss and length, made with an OLTS |
| Tier 2 | the extra fibre test of a trace, made with an OTDR |
| OLTS | optical loss test set: a light source and power meter |
| OTDR | a tool that sends pulses of light and reads what comes back |
| Reference cord | a short, very clean test cable used to set the zero point |
| Launch cable | a cable between the OTDR and the link so the first connector shows |
| Event | a point on a trace where light is lost or reflected, such as a join or a bend |
| Wavelength | the colour of the light, measured in nanometres |
The cells students fill in are left blank in this preview.
By the end of this lesson
Note
I can describe the three fibre tests, put them in order, and record the results.
Starter: copper tests and fibre tools
Have a go
Starter: copper tests and fibre tools
3 questionsYour answers are marked here and are not kept. A college account keeps every student’s marks.
Never look into a live fibre
Warning
The light cannot be seen and can harm your eyes. Check the source is off before you open a connector. An inspection viewer has filters, but you still never look straight into a fibre.
Step 1: inspect and clean
Before any fibre test, inspect each connector end with a fibre inspection tool. The viewer shows the end on a screen. Look for dust, oil and scratches. Clean it, then inspect again. A standard sets the pass zones: the centre must be spotless.
Keep dust caps on until the moment of use.
Step 2: tier 1 with an OLTS
The OLTS has a light source at one end and a power meter at the other. First set the reference with clean reference cords, so the meter reads zero for a perfect link. Then connect the link and measure the loss.
Test at both wavelengths for the fibre type. A tier 1 test gives the loss and the length.
Check: inspect and tier 1
Have a go
Check: inspect and tier 1
3 questionsYour answers are marked here and are not kept. A college account keeps every student’s marks.