Fiber optic transmission wavelengths are determined by two factors: longer wavelengths in the infrared for lower loss in the glass fiber and at wavelengths which are between the absorption bands. Thus the normal wavelengths are 850, 1300 and 1550 nm. Fortunately, we are also able to make. The telecommunication transport technologies move from copper based networks to optical fiber, from timeslot based transport to wave length based transport, from traditional circuit switching to terabit router and all optical based networks entering into a new era of optical networking. The. The document discusses the optical communication system used in the Indian Railways, managed by RailTel Corporation, which focuses on creating a nationwide broadband telecom network to enhance operational safety.