The definition of a claim term in the specification is controlling over extrinsic evidence even when that evidence points to a broader understanding of the plain meaning of the term in the art. Here, for example, an “active” waveguide coupler was found to be clearly defined in the specification as requiring the capability of being optically pumped to provide gain, even though it was not so clearly limited in the art at large. “We need not reach [the extrinsic evidence] here, as the intrinsic evidence fully determines the proper construction of the contested claim term.” It may therefore be best to avoid narrowing definitions of known terms in the specification unless necessary for patentability over the prior art.
Background / Facts: The patent being asserted here is directed to the use of “an active waveguide coupler” to facilitate the coupling of multiple lasers into a single fiber optic cable. The specification explains that optical components can be made of either active materials or passive materials. Active material is capable of being pumped to provide gain, thus increasing the intensity of the light traveling through it. Conversely, passive material does not allow for the light traveling through it to increase intensity, even when pumped.
Issue(s): Whether the definition of “active” in the specification is controlling over broader extrinsic evidence.
Holding(s): Yes. “The [] patent specification clearly defines ‘active’ and ‘passive.’ An active region or component is one that is made of active material, which is capable of being pumped to produce gain to an optical signal. This description of the active region is found repeatedly throughout the specification. [] Furthermore, the specification draws a distinction between active and passive material, by specifically defining passive material as material not capable of being pumped. [] [The patentee] points to nothing in the intrinsic record—and we cannot find anything—that indicates that passive material is capable of producing gain when pumped. Thus, the ability to provide gain when pumped is required for a material to be active, and therefore must be required of the ‘active waveguide coupler.’”