M. J. CREANER, R. C. STEELE, I. MARSHALL, G. R. WALKER, N. G. WALKER, J. MELLIS, S. AL CHALABI, J. DAVIDSON, I. STURGESS, and P. COCHRANE, "Field demonstration of a 565-Mbit/s DPSK coherent optical system over 176 km of installed fiber,"
in Optical Fiber Communication Conference,
Vol. 5 of 1989 OSA Technical Digest Series
(Optical Society of America, 1989), paper TUI8.