Greenlee 560XL Instruction Manual page 20

One Test Jumper Method: Connector Loss (cont'd)
2. Ensure that the light source is in continuous wave (CW) output
mode. Set the optical power meter to the appropriate wavelength
(using the [λ] key) and to dBm units (using the [dB/dBm] key).
Note that the dBm output of the reference cable should be within
acceptable limits.
3. To store the reference level, press the [dB/dBm] key on the optical
power meter until the "r" annunciator appears on the LCD screen
(about 3 seconds). The display should read 0.00 dB. See below.
20
Press the
[dB/dBm]
key to set the
0 dB reference