Abstract: An optoelectronic package includes an optical fiber cable assembly and feedthrough assembly which provide high performance and high reliability optical fiber alignment, locking and sealing. An optical fiber is fed through a nose tube into the package. The fiber is selectively metallized at its end. A solder lock joint on a substrate on the package floor preferably of an SnAg- based or SnSb- based solder. It surrounds at least part of the metallized portion of the fiber so as to hold the fiber in its desired position, in alignment with an optoelectronic device in the package. With Sn metallization on the fiber, this results in a highly reliable solder lock joint. A solder seal joint forms a hermetic seal between the nose tube and the Au metallized fiber. This solder is preferably 80Au20Sn. A rigid cylindrical seal tube sleeve insert on the fiber is designed to guide the fiber into the nose tube without bending or damaging the fiber.