DEFINITION OF TERMS
KI23400/KI27400 UM-2
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Definition Of Terms
Power Meter
Power Range:
The range of input powers for which the instrument
can be used.
Maximum Input Power:
The input power not to be exceeded to avoid
destroying the instrument.
Uncertainty at Reference Conditions:
The uncertainty for the
specified set of reference conditions, including all uncertainties in the
calibration chain from the national laboratory to the test meter
(connectors and test leads must be absolutely clean and undamaged).
Reference conditions are the conditions during the responsivity
calibration.
Total Uncertainty:
The uncertainty for a specified set of operating
conditions, including noise and drift (connectors and test leads must
be absolutely clean and undamaged).
Autotest Sensitivity:
The power level below which Autotest does not
work.
Light Source
Output Power:
The CW output power at the specified
λ
, at the end of
a reference cable.
Power Uncertainty / Repeatability:
Uncertainty in power level at the
end of a reference cable.
Short / Long Term (Power) Stability:
In CW mode, the uncertainty
of the power level observed over a given time, compared to the mean
power during this time. Measured with an averaging optical power
meter, a 9/125µm fiber, at constant temperature, within a specified
temperature window, and at line voltage.
Centre wavelength:
The
λ
representing the centre of mass of the
selected peaks:
CW = (1/ Po)
( P
i
i
),
where Pi and
i are the power and
λ
of each spectral component and Po is the total
power.
Spectral Bandwidth:
FWHM (full width at half the maximum)
describes the spectral width of the half-power points of the laser,
assuming a Gaussian envelope of the spectral power distribution. The
half-power points are those where the power-spectral density is one
half of the peak amplitude of the Gaussian curve:
and
where:
= centre
λ
of laser diode (in vacuum)
P
=
P
i
= total power, in watts
P
= power of
i
th
longitudinal mode
=
λ
of
i
th
longitudinal mode (in vacuum)
M
= multiplication factor; for a source with a Gaussian envelope
M
= 2.35; for other types of spectra, use
M
= 2.35 as well
