Patent ID: 7325984

Claim:
An optical subassembly mating with an optical connector that is attached to a tip of an optical fiber, comprising: an optical receptacle securing a stub optically coupled with the optical connector, the stub providing a coupling fiber in a center portion thereof; an optical device including a semiconductor optical device, a stem for mounting the semiconductor optical device, and a lens cap assembled with the stem, the lens cap securing a lens to couple the semiconductor optical device with the coupling fiber; and a joint sleeve for aligning the optical receptacle with the optical device, wherein a distance between the semiconductor optical device and the lens is greater than a focal length of the lens and a reference distance where a maximum coupling efficiency between the semiconductor optical device and the lens is achieved such that a defocused distance between the coupling fiber and the lens is shorter than a distance when the semiconductor optical device is set in the reference distance to get a predetermined optical output power from the optical subassembly.