Allied Telesis AT-2911 Series Adapters - Manual (Page 120)

Appendix A: Cleaning Fiber Optic Connectors
120
3. If a fiber inspection scope is available, use the scope to inspect the
connector to make sure that it is clean and to check for scratches, pits,
or other problems that may affect performance.
Note
Always keep a dust cap on a fiber optic cable when it is not in use.
Warning
Do not stare into the laser beam.  L2
Warning
Do not look directly at the cable ends or inspect the cable ends with
an optical lens.
 L6