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Tutorial 5: Use Software Filters
This tutorial enables a software filter. The filter is designed with user fre-
quency corrections. User frequency corrections can be used for:
• Removing the effects of frequency response roll-off due to the optical-to-
electrical converter and cables.
• Simulating hardware filters recommended for laser transmitter evaluation,
such as 4th-order Bessel- Thomson filters.
The eye-diagram analyzer must be in eyeline mode to apply user-corrections.
In eyeline mode, each sweep produces a continuous trace with the points con-
nected. (This is opposed to unconnected dots with the eye mode.) Eyeline
mode is especially useful for measuring variations in laser turn-on delay, over-
shoot, and ringing and for applying user frequency corrections. The compati-
ble mode is eyeline.
Several Bessel-Thomson software filters are included on the 70874A eye-dia-
gram analyzer's memory card. These filters can be applied as user-corrections
in the eyeline and pattern modes. (User corrections must be off in eye mode.)
User correction files are identified by the prefix a_ as shown in the following
table. Two additional files on the card, AUTOST and 70874, comprise the eye-
diagram analyzer program.
Supplied User-Correction Files
File Name
File Data
a_bt248832
4th order Bessel- Thomson filter for 2.48832 Gbit/sec transmission.
a_bt_62208
4th order Bessel- Thomson filter for 622.08 Mbit/sec transmission.
a_bt_15552
4th order Bessel- Thomson filter for 155.52 Mbit/sec transmission.
Application Tutorials
Tutorial 5: Use Software Filters
2-15
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