Atec Agilent-81618A - Manual (Page 25)

Definition of Terms Specifications
Agilent 81618A/9A and Agilent 81622B/3B/4B/6B/7B/8B User’s Guide, Second Edition
25
Conditions: constant wavelength, constant power level, angled
connector as specified, linewidth of source <100 MHz, temperature as
specified.
N O T E Spectral ripple is measured by stepping the source wavelength over
the wavelength range specified.
Relative uncertainty due to speckle noise
This is the uncertainty of the power reading when using a coherent
source. This is due to a variation of the power meters responsivity
caused by optical interference
1
between different optical paths within
the power meters optical assembly.
Conditions: constant wavelength, constant power level, angled
connector as specified, linewidth of source as specified, temperature
as specified.
1
Incoming light to the integrating sphere undergoes numerous
internal reflections (as many as several hundred) prior to hitting
the detector. If the source is sufficiently coherent, a complicated
interference pattern (speckle pattern) appears spread over the
whole sphere volume. Slight changes of the ambient conditions
(temperature, vibration, shock) affect particular optical paths
which consequently changes the speckle pattern and results in an
instability of the head power reading (speckle noise).
N O T E Changes in the source wavelength have a similar effect on speckle
noise as environmental changes, because they cause fluctuations in
the interference pattern. If the source coherence length is small
compared to the effective path length, the interference pattern
disappears and relative uncertainty due to speckle noise becomes
negligible.
Measurement: In contrast to the spectral ripple definition the source
wavelength isn’t stepped when measuring speckle noise.
Relative uncertainty due to polarization
Also termed polarization-dependent responsivity (PDR), the relative
uncertainty due to polarization is the uncertainty of the displayed
power level on the input polarization state, expressed as the difference
between the highest and the lowest displayed power. Uncertainty
figures are based upon a 95% confidence level.
Conditions: laser source with variable polarization state, generation of
all possible polarization states (covering the entire Poincaré sphere),
constant wavelength, constant power level, angled connector as
specified, temperature as specified.