(According to Dr. Steve Herbert from the Xavier University Physics Department)
I would call this a water fiber optical cable. I use a 2 liter bottle filled with water and with a hole in the side (initially corked). I line up a laser from the back side of the bottle (opposite the hole) so that the laser beam goes through the water and hits the cork. When I remove the cork, the water streams out and, because of internal reflection, the laser beam stays contained in the stream and follows it down into the pan. This is the same physics behind all of the fiber optic communication lines except the lines are a little more flexible.