Number 20 (Story #3), February 5, 1991 by Phillip F. Schewe and Ben Stein ERBIUM DOPED FIBER AMPLIFIERS (EDFA's) will soon facilitate the carrying of optical communications at gigabit rates over fiber links thousands of kilometers long. According to Emmanuel Desurvire of Columbia University, the use of erbium doping in small amounts in the optical fibers "makes it possible to distribute the gain over the fiber itself, thereby minimizing the power excursion of the signal. Such an approach makes possible virtually lossless signal transmission from one fiber network to the next." AT&T and the Japanese company KDD agreed recently to lay jointly a cross-Pacific cable capable of carrying 600,000 phone conversations simultaneously. In this case the optical signals will be amplified by EDFA's spaced every 20 to 30 miles. (Optics and Photonics, Jan. 1991.)