A fiber coupled semiconductor device having an improved optical stability with respect to temperature variation is disclosed. The stability improvement is achieved by placing the platform holding the semiconductor chip and the optical fiber onto a spacer mounted on a base. The spacer has an area smaller than the area of the platform, for mechanical decoupling of thermally induced deformation of the base from a deformation of the platform of the semiconductor device. Attaching the optical fiber to a vertical mounting surface of a fiber mount, and additionally attaching the fiber mount to a submount of the semiconductor chip further improves thermal stability of the packaged device.