EXFO FTB-500 - Manual (Page 288)

Maintenance
280 FTB-500
Installing or Removing the Power Meter and VFL
Installing or Removing the Power Meter and
VFL
If your unit was not equipped with a power meter and a VFL at time of your
initial purchase, you can purchase one afterwards and install it yourself.
You may also need to remove the power meter to send it to an authorized
service center for recalibration.
Note: If you prefer not to remove the power meter from your unit when a
calibration is needed, you can also send the complete unit to the service
center.
W
ARNING

To avoid serious injuries as well as irreparable damages both to
your unit and your power meter, ALWAYS TURN OFF YOUR UNIT
(shutdown mode, not sleep), DISCONNECT IT FROM THE
EXTERNAL POWER SOURCE, and REMOVE ALL BATTERIES. For
more information on the ways to turn off your unit, see Turning
Off Your Unit on page 32.

Be careful not to drop metal objects such as screws inside the
unit. These could cause a short-circuit leading to a fire or an
explosion.