1. A. Selvarajan, S. Kar, T. Srinivas: Overview of optical fiber communications. In: Optical Fiber Communications, ed. by G. Keiser (McGraw-Hill, New York 2002)
2. A.G. Bell: The photophone, Science os-1(12), 130–134 (1880)
3. T. Aruga: Spatial Transmission Optics (Suiyosha, Tokyo 2000)
4. S. Endo: History of Light (Tosho, Tokyo 1977)
5. Nakagawa Laboratories: Illuminative light communication device, JP3827082 (2006) and US7583901 B2 (2009)