EXFO IQS-12002B Calibration System - Manual (Page 70)

Calibration Methods
66 IQS-12002B
Power Meter
To cover a bigger area of the power meter range, once the test done by
decreasing the power is completed, shift the first attenuator by 1.5 dB and
then start the test at increasing power levels.
Typical uncertainties of this method include:
³
All possible power fluctuations while measuring P
a
, P
b
, and P
total
such
as fluctuations of the source due to drifts.
³
Improper balancing of the output powers of each coupler branch (P
a
and P
b
). If balancing is not correctly done, the global linearity cannot
be easily inferred).
³
Sensitivity to changing reflections.
³
Instabilities due to interference if the coherence length of the laser is
too large.
³
Polarization sensitivity of the power meter and attenuators (when
applicable).
³
Resolution of the power meter.
³
Difference between the individual powers of each step (P
a
,
i
and P
b
,
i
)
compared to the total power of the next step (P
total,i+1
) (for calculating
global linearity).