Bristol 428 - Page 12

Model 428 User’s Manual OPERATION
Bristol Instruments, Inc. 12
 Wavelength Units and Medium – Identifies the units chosen for the
measurement of wavelength (nm), wavenumber (cm
-1
), or frequency (THz).
Also identifies the medium to which the measurement is referenced. The
options are vacuum (-vac) or standard air (Std Air) at 20°C, 760 mm Hg, and
0% relative humidity. The Wavelength Units and Medium can be changed
from Config Screen 1.
 Power – Displays the measured optical power in the user selected units.
 Power Units – Identifies the units chosen for the measurement of power.
The options are mW or μW (scaled automatically) or dBm. This parameter
can be changed from Config Screen 1.
 Peak/Chan/FPAv – Identifies the channel or measurement method
displayed. Use the Select button to highlight the displayed measurement
method, and the Change or Arrow buttons to cycle through the three options.
– Peak – Displays the wavelength of the highest power channel. The
channel number is given below the wavelength units.
– Chan – Displays the wavelength of a user-selected channel. The
channel number is indicated below the wavelength units, and can be
changed using the Arrow keys.
– FPAv – Displays the power-weighted average wavelength of all peaks
measured. This is useful when the center wavelength of a group of input
lines is desired, such as that of a typical Fabry-Perot laser.
 Average (AVG) – The instrument displays the results from each
measurement, or the result from an averaged number of measurements
(2, 4, 8, 16, 32, 64, or 128) chosen in Config Screen 1. The instrument will
display a measurement after the chosen number of interferograms is
collected, averaged, and analyzed. For averages between 2 and 32, the
display will then be updated with each successive measurement. For
averages of 64 or 128, the display will be updated after each block of
interferograms has been averaged.
Use the Select button to highlight the Average value, and the Change or
Arrow buttons to cycle through the averaging states. Off indicates that the
average function is disabled, while a numeric value indicates that an average
is being calculated.
 Power Offset (Poffs) – The instrument can adjust the power measurement
to account for an external attenuator by using a Power Offset value equal to
the external attenuation. This is useful if the optical input power would
otherwise exceed the maximum measurable input of 10 mW (10 dBm). The
Power Offset value (1-20 dB) is chosen in the Config Screen 1.
Use the Select button to highlight the Power Offset value, and the Change or
Arrow buttons to adjust the Power Offset state. Off indicates that the Power
Offset is disabled, while a numeric value indicates that the Power Display is
adjusted by the specified Power Offset.