Fiber-optic cable

The optical fiber elements are typically individually coated with plastic layers and contained in a protective tube suitable for the environment where the cable is used.

Optical fiber consists of a core and a cladding layer, selected for total internal reflection due to the difference in the refractive index between the two.

For indoor applications, the jacketed fiber is generally enclosed, together with a bundle of flexible fibrous polymer strength members like aramid (e.g. Twaron or Kevlar), in a lightweight plastic cover to form a simple cable.

Each end of the cable may be terminated with a specialized optical fiber connector to allow it to be easily connected and disconnected from transmitting and receiving equipment.

Instead of a loose tube, the fiber may be embedded in a heavy polymer jacket, commonly called tight buffer construction.

Breakout cables normally contain a ripcord, two non-conductive dielectric strengthening members (normally a glass rod epoxy), an aramid yarn, and 3 mm buffer tubing with an additional layer of Kevlar surrounding each fiber.

[3] Distribution cables have an overall Kevlar wrapping, a ripcord, and a 900 micrometer buffer coating surrounding each fiber.

These fiber units are commonly bundled with additional steel strength members, again with a helical twist to allow for stretching.

This is accomplished by use of solid barriers such as copper tubes, and water-repellent jelly or water-absorbing powder surrounding the fiber.

Modern cables come in a wide variety of sheathings and armor, designed for applications such as direct burial in trenches, dual use as power lines, installation in conduit, lashing to aerial telephone poles, submarine installation, and insertion in paved streets.

In September 2012, NTT Japan demonstrated a single fiber cable that was able to transfer 1 petabit per second (1015bits/s) over a distance of 50 kilometers.

[citation needed] Optical fibers are very strong, but the strength is drastically reduced by unavoidable microscopic surface flaws inherent in the manufacturing process.

Some common jacket materials are LSZH, polyvinyl chloride, polyethylene, polyurethane, polybutylene terephthalate, and polyamide.

This is the speed of light in vacuum divided by the refractive index of the glass used, typically around 180,000 to 200,000 km/s, resulting in 5.0 to 5.5 microseconds of latency per km.

POF is large core (about 1 mm) fiber suitable only for short, low-speed networks such as TOSLINK optical audio or for use within cars.

The eye's natural defense against sudden exposure to bright light is the blink reflex, which is not triggered by infrared sources.

[24] In some cases the power levels are high enough to damage eyes, particularly when lenses or microscopes are used to inspect fibers that are emitting invisible infrared light.

Considerations such as fire resistance, Nationally Recognized Testing Laboratory (NRTL) Listings, placement in vertical shafts, and other performance-related issues need to be fully addressed for these environments.

Innerducts are installed in existing underground conduit systems to provide clean, continuous, low-friction paths for placing optical cables that have relatively low pulling tension limits.

Beyond the basic profiles or contours (smoothwall, corrugated, or ribbed), innerduct is also available in an increasing variety of multiduct designs.

Multiduct may be either a composite unit consisting of up to four or six individual innerducts that are held together by some mechanical means, or a single extruded product having multiple channels through which to pull several cables.

Innerducts are primarily installed in underground conduit systems that provide connecting paths between manhole locations.