Measurements were made of optical signals used in the Virtual Guard version of "virtual walls" used by Samsung, the same on Powerbot and Navibot.
This system uses a signal from the robot to activate the Guard only when nearby to save the battery in the Guard. Technical details found posted at
http://www.robotreviews.com/chat/viewtopic.php?f=4&t=20151&p=145468#p145468
Newer models in the U.S. since 2016 have switched to mag strip boundaries similar to Neato Robotics. The optical Virtual Guards lack focus of the beams and can be confused by reflections off walls, so is not a perfect system. Broad beams can work with random navigation robots like the Roomba on which originally used, but the systematic guided robots need to probe and map the shape of boundaries.