An arrangement (apparatus and method) for hermetically sealing a fiber optic device to preserve its optical characteristics. The fiber optic device includes a device body such as an optical coupler or a multiplexer and optical fibers. Aluminum metal seals are formed on exposed regions of the optical fibers to provide an interface between the optical fibers and an enclosure. The metal seals may be formed directly on the optical fibers or by heating and compressing an aluminum sleeve onto an enclosure having an aluminum surface layer. The aluminum sleeve and surface layers melt and deform around the optical fibers, hermetically enclosing the fiber optic device.