Optical Spectrum Analyzers
Chapter 4: Description
Rev D, June 16, 2022
Page 12
features. More data points close to a sharp spectral feature can make it easier to determine a peak’s center
frequency or intensity.
In the ThorSpectra software, a zero fill factor (ZFF) of 1 means that the interferogram is made twice as long
(equally many zeroes as true data points) and ZFF = 2 means that the interferogram is made four times as long
(three times more zeroes than data points).
It is important to note that since no real data is added, the resolution of the final spectrum does not change. This
means that, for example, two peaks located close to each other in frequency would not be more resolvable if
ZFF = 2 were used, rather than ZFF = 0.
4.12.
Software
The OSA is shipped with the software package pre-installed on the laptop computer that is included with the
purchase of this instrument. The software has a customizable graphical user interface for acquiring, inspecting,
manipulating, and analyzing spectra and interferograms. The software makes it easy to locate and track spectral
peaks or valleys, measure the optical input power over any wavelength range, calculate an absorption spectrum
in real-time, or track a large number of parameters over time. A device interface library containing a multitude
of routines for data acquisition, instrument control, and spectral processing and manipulation is also provided
with the instrument. The library can be used to develop customized software for your own application using
python, LabVIEW
®
, C/C++, C#, or other programming languages. Each OSA ships with a set of LabVIEW
®
routines to assist with writing user defined applications. More information on how to operate the software can
be found in Chapters 8 and 9.
4.13. Trigger (Redstone OSA305 only)
At the back panel of the Redstone OSA305 instrument, there are four BNC connectors, some of which can be
used to externally trigger a measurement. The four BNC connectors are labeled on the instrument back panel
and provide the following functionality:
Trigg
: When the negative flank of a signal is registered by this input, the Redstone OSA will start an
acquisition with the current settings. Note that the trigger will be ignored unless the output Aux out is
low, due to the fact that the retroreflector first needs to move to the correct starting position.
Acquiring data
: This output will be high while the data acquisition is active.
Aux in
: Currently not used.
Aux out
: When this output is low, the instrument is ready to receive an external trigger via the Trigg
input. When high, the instrument is busy.
More detailed specifications for these connectors can be found in Section 11.5 Trigger Specifications (Redstone
OSA305 only).
To perform a triggered measurement, the following steps should be followed:
1. The Trigger Type combo box in the Settings menu’s Acquisition tab must be set to “External.”
2. Click the “Single” or “Repeat” button.
3. Check that Aux out is low and send trigger to the Trigg input.
4.14. Interlock (Redstone OSA305 only)
The Redstone OSA305 devices are equipped with a phono-type interlock jack located on the back panel. This
is a laser safety feature for the internal reference laser source. To enable the reference laser source, a short
circuit (< 430 Ω) must be applied across the terminals of the interlock connector. The shorting device (interlock
pin) installed in all units shipped from Thorlabs performs this function. Leave the shorting device installed unless
using an external safety circuit or other type of remotely controlled switch to enable laser output. Making use of
the interlock feature requires the appropriate 2.5 mm phono-type plug, which is readily available through most
electronics retailers. The plug should be wired to the external safety circuit or switch and then plugged into the
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