Abstract: Apparatus for optical communications (10, 20, 30, 60 90) includes an optically switched resonant tunneling device (12, 22, 42, 62, 92) being exposed to an input light. The optically switched resonant tunneling device (12, 22, 42, 62, 92) generates a first and second voltage levels in response to the intensity level of the input light. A lasing device (16, 28, 46, 68, 74, 100) is coupled to the optically switched resonant tunneling device (12, 22, 42, 62, 92). The lasing device (16, 28, 46, 68, 74, 100) generates and modulates an output light in response to the first and second voltage levels.

Abstract: A semiconductor wafer is manufactured to include plural integrated circuit dies and plural probe area pads separate from the integrated circuit dies. The wafer also includes die selector circuits separate from the integrated circuit dies and the probe area pads. There is one selector circuit for each die. Each selector circuit produces a mode signal electrically connected to a mode bond pad of that one die. Each die selector circuit has at least a pair of I/O terminals bi-directionally electrically connected in series to at least two probe area pads.