Abstract: In a WDM optical transmission system employing optical amplifiers in its transmission path, a supervisory signal channel, used for monitoring and controlling the operation of the amplifiers and spectrally separated from the data transmission, may be multiplexed with the data. A construction of amplifier is disclosed which is capable of being upgraded with an upgrade of the transmission system to include additional data handling capacity, for instance data transmission in an additional waveband and/or in the opposite direction, without interruption of the pre-upgrade data transmission path through the amplifiers. This is accomplished by the use of channel dropping and insertion filters disposed so that the amplifying data transmission path extends via the drop/insertion channel of those filters.

Abstract: A high frequency, e.g. millimeter wave, semiconductor diode structure includes a buried layer of n.sup.+ -type material and a surface layer of lightly doped n-type material on which a Schottky barrier contact is disposed. The n.sup.+ -type layer provides a low series resistance thus permitting high frequency operation. The structure is compatible with MESFET processing techniques and may thus be incorporated in an integrated circuit.

Abstract: A millimeter wave integrated circuit (MIC) includes both low power components and high power components, e.g. Gunn diodes, disposed on a common semi-insulating semi-conductor substrate. Each high power component is formed in an active epitaxial layer and is provided with a heat sink comprising a thermally conductive material deposited in an opening in the back of the substrate below the compound. The low power components are isolated by an implanted proton layer.