Wafer-level testing is performed on an electronic device to be used in
an optical communications system. An optical test signal is generated and is provided
to a first photo detector. An electrical output of the first photo detector is
supplied to the electronic device on the wafer. An electrical output from the electronic
device on the wafer is used to drive a light source. An optical output of the light
source is supplied to a second photo detector and an electrical signal output from
the second photo detector is examined.