Optical network unit

An optical network unit for field installation adjacent to an optical fiber transmission line, for separating multiplexed video and telphony signals for delivery to subscribers' residences as electrical signals over metallic drop cables, comprising:

• a hollow housing formed of heat-conductive material with an open from end and an open rear end,
• a front cover dimensioned for removable mating installation on the housing for sealingly closing the open front end,
• a rear cover dimensioned for removable mating installation on the housing for sealingly closing the open rear end,
• cable entrance port means formed in said housing accommodating cables connecting with the transmission line and the subscribers' residences,
• a backplane assembly mounted in said housing near its rear end incorporating optical-to-electrical signal conversion components and connectors for electrical signals,
• card-supporting slot means formed in the interior surfaces of the housing, positioning a plurality of printed circuit board cards for sliding installation therein into electrical contact with said backplane assembly,
• a plurality of thin, flat internal fins each protruding inward from an outer wall of the housing into and partway across its hollow interior adjacent to one of the plurality of printed circuit board cards, and presenting exposed fin surface area closely juxtaposed to a major portion of the exposed area of said one printed circuit board card,
• whereby printed circuit board cards are readily installed by insertion through the open front housing end into sliding engagement with said slot means, and heat produced by the printed circuit board cards within the housing after its open ends are sealed by said covers is delivered by radiation to said closely juxtaposed fins and by internal convection between said internal fins and cards and thence to the hollow housing from which it is dissipated to the ambient atmosphere primarily by radiation and convection.