Y. Kudo, M. Fuse, S. Morikura, K. Utsumi, and S. Kitaji, "Required quality for multichannel digital modulation signals in the transmission system employing optical super wideband FM technique,"
in Optical Fiber Communication Conference,
Vol. 2 of 1998 OSA Technical Digest Series
(Optical Society of America, 1998), paper WM18.