EXFO PM-1100 Optical Power Meter - Manual (Page 26)

Operating the Optical Power Meter
16 PM-1100
Relative Power
Relative Power
In relative mode, the Optical Power Meter compares the power of the
signal received at the detector port to a preset reference value in dBm or
watts. The relative power is equal to the absolute power minus the
reference value, therefore
³
a negative measurement indicates that the received power is below
the reference value, and
³
a positive measurement indicates that the received power is above the
reference value.
To activate relative mode, press dB/ Δ W. Once in relative mode, pressing
dB/ Δ W switches between dBm and watt measurements units for the
relative power and reference value. If necessary, press
λ
to toggle between
the wavelengths in the shortlist (to edit the shortlist of wavelengths
see Customizing the Shortlist of Wavelengths on page 33).
dBm
dB
Relative power
Unit of measurement
for the relative power
Reference value Unit of measurement
for the reference value