K. Thyagarajan has been working in the general area of Photonics and in particular in Fiber 2 Optics since 1973 and has published more than 125 research papers in international journals and coauthored seven books with Professor Ajoy Ghatak. He has been teaching courses related to Lasers, Fiber Optics, Quantum Electronics, Optical Electronics, Electromagnetics since the past thirty years. Thyagarajan was elected Fellow of the Optical Society of America in 2005, was honored in 2003 with the title "Officier dans l'ordre des Palmes Academiques" by the French Government and was awarded the "Fiber Optic Person of the Year 1997" award (jointly) by Lucent Technologies- Finolex and Voice and Data. He was a consultant to Tejas Networks India Pvt. Ltd., Bangalore and has held visiting positions in Thomson-CSF, France and University of Florida, Gainesville, USA. Ajoy Ghatak has recently retired as Professor of Physics from IIT Delhi. He obtained his MSc from Delhi University and PhD from Cornell University. His research areas are Fiber Optics and Quantum Mechanics. He has several books in these areas and some of them have been translated into foreign languages. The first edition of OPTICS has been translated into Chinese and Persian. Professor Ghatak is a recipient of several awards including the 2008 SPIE Educator Award in recognition of his unparalleled global contributions to the field of fiber optics research, and his tireless dedication to optics education worldwide and throughout the developing world in particular. He has also received the 2003 Optical Society of America Esther Hoffman Beller award in recognition of his outstanding contributions to optical science and engineering education. Furthermore, he is a recipient of the 1979 CSIR S S Bhatnagar award, the 1990 UGC Meghnad Saha award, the 2003 International Commission for Optics Galileo Galilei award and the 2007 Lifetime Achievement Award of the Optical Society of India.