Abstract: A protectively sealed package enclosing an optical component included in a light transmission system in which fiber-optics lines are connected to the component, the lines feeding through the package without breaking the seal. The package includes a tray to accommodate the optical component, a lid to close the tray, and a sealing unit formed of elastomeric material to define a loop and a jacket integral therewith. The sealing unit is sandwiched between the tray and the lid, the loop being seated on a ledge that runs along the rim of the tray and the jacket projecting outwardly therefrom. The jacket is provided with a duct through which extend the fiber-optics lines connected to the optical component, the duct being air-tight. When the lid is fastened to the tray it then compresses the loop therebetween to protectively seal the package.