Tyco Submarines Systems Ltd., based in Morristown, N.J., has demonstrated in a laboratory experiment transmission of 64 10-Gb/s WDM channels on a single fiber path over a distance of 7200 km, representing an overall capacity of 640 Gb/s per fiber. The experiment also limited the linear and nonlinear reactions between channels, which enabled a spectral efficiency of 33 percent. The tests were conducted at Tyco's R&D laboratory in Eatontown, N.J. Researchers used a 64-channel WDM transmitter and a 516-km amplifier chain, which was arranged in a circulating loop using large-mode optical fiber.