3-4
IM AQ7280-01EN
Ghost Cursor
The ghost cursor is used to check for secondary reflections. A secondary reflection is a reflection
that is detected in a location where no event actually occurs.
OFF: The ghost cursor is not displayed.
ON: The ghost cursor is displayed.
Secondary reflection
Ghost cursor
Turn the rotary knob to move to the next
secondary reflection detection point.
• How Secondary Reflections Are Generated
The optical pulse that is generated from position I in the following figure propagates in the
direction of II.
↓
Light ray A that is reflected at connection II in the figure is reflected again at connection I and
propagates in the direction of II as light ray B. At this point, the AQ7280 detects A as an event.
↓
B is again reflected by connection II, and this generates reflected light ray C. At this point, the
AQ7280 detects C as an event.
Because the AQ7280 measures all the reflected light rays, A, C, and D, C is also detected as an
event in the same manner that an actually generated reflection is. Therefore, while there is no
actual event in this location, it appears as if an event has in fact occurred.
Distance 2L
Distance L
Optical fiber cable connection
I
II
III
A
B
A
C
D
C
D
Secondary
reflection
3.2 Configuring the Waveform Display