Corning Incorporated has filed a lawsuit against FiberCore Inc., claiming the company violated one of its optical fiber patents. Corning filed suit in the US District Court in Worcester, Mass., on Jan. 8. In response, FiberCore denied it had violated any Corning optical fiber patent and said it had not sold any fiber in the US. It asked Corning to withdraw the patent infringement lawsuit. FiberCore, established in 1993, has a manufacturing facility in Jena, Germany, and plans to build a plant in Charlton, Mass. The company sells preforms (the blanks from which optical fiber is drawn) and fiber for the telecommunications network and local area networks.