S. Chandrasekhar and Xiang Liu, Bell Labs, Alcatel-Lucent, 791 Holmdel-Keyport Road, Holmdel, NJ 07733, USA
The authors are especially grateful to their colleagues working in this field in Bell Laboratories, Alcatel-Lucent, for fruitful collaborations and valuable discussions. Among them are L.L. Buhl, E.C. Burrows, R. Essiambre, A.H. Gnauck, and P.J. Winzer. The authors also wish to thank A.R. Chraplyvy, R.W. Tkach, and P.J. Winzer for their support.