Subsea Cables & Internet Infrastructure

Each fibre strand consists of the core and the cladding. The core is like a one way road for the light to traveland cladding are the guardrails that prevent it from escaping. The refractive index measures how fast light traverses a given medium. It is defined as the ratio of the speed of light in a vacuum to the velocity of light via the medium. The core has a higher refractive index than the cladding. As long as the refractive index differential is large enough, photons that hit the cladding at a critical angle or less will bounce back into the core. Physicists call this bouncing of light internal reflection. So the core/cladding structure is designed to preserve the optical power or amplitude of the wavelengths. It minimizes optical attenuation, the great enemy of optical networking along with chromatic and polar dispersion.  The bottom middle chart shows that optical attenuation, which reflects opposing forces, reaches a minimum in the C band. The C band is defined as wavelength...

  A good primer on the physical structure of an optical fibre strand with some basic physics to give you insight into how it really works. Optical fibre is an ultra pure, high quality glass designed to carry infrared laser signals encoding bits, in other words, zeros and ones. It consists of a core which is the optical highway for the laser light, a cladding designed to protect the core and prevent external light from reaching the core or light traversing the core from escaping, and finally, soft and hard plastic coatings as further protection. For full details, see https://learn.aflglobal.com/enterprise/the-basic-structure-of-optical-fiber.