Although an optical fiber is very thin, it is composed of two kinds of glass and a protective outer shield. Specifically, these are the:
- Core: Consists of pure glass and is the part of the fiber where light is carried.
- Cladding: The glass that surrounds the core and acts as a mirror. The light pulses propagate down the core while the cladding reflects the light pulses. This keeps the light pulses contained in the fiber core in a phenomenon known as total internal reflection.
- Jacket: Typically a PVC jacket that protects the core and cladding. It may also include strengthening materials and a buffer (coating) whose purpose is to protect the glass from scratches and moisture.
Although susceptible to sharp bends, the properties of the core and cladding have been altered at the molecular level to make it very strong. Optical fiber is proof tested through a rigorous manufacturing process for strength at a minimum of 100,000 pounds per square inch. Optical fiber is durable enough to withstand handling during installation and deployment in harsh environmental conditions in networks all around the world.