Nortel Networks Corp. is shutting down the optical components business it acquired in March 2000 as CoreTek Inc. The Boston-based division, which developed tunable lasers and other components for optical carrier networks, fell victim to the glut in carrier network capacity and the resulting slump in infrastructure building, said David Chamberlin, a spokesman for Nortel. As a result of the closure, Nortel will eliminate 160 jobs. Nortel, in Brampton, Ont., agreed to buy CoreTek in a deal worth up to US$1.43 billion in stock shortly before the April 2000 technology stock crash.