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Learn more about the communication technology that carries 99% of all data transferred nowadays.

18

Apr, 19

Fiber Optics: Harness the Speed of Light

We are used to transmitting data through regular copper wires, however they come with a great deal of disadvantages. The reason for this is that copper wires use electrical signals to transmit data, creating challenges such as signal degradation, electromagnetic interference and low bandwidth limits. At some point in the last century, the entire internet relied on copper wires for worldwide data transmission, however innovation came from a completely unexpected direction. In the 1950s, optical fibers were originally developed for use in endoscopes to help doctors see inside the human body without cutting it open. Approximately ten years later, engineers found a way to use optical fibers to transmit telephone calls at the speed of light (normally it would be around 300,000 km/s, however inside the fiber optic wire it slows down to around two thirds of that). These developments set the foundation to what is nowadays the main data transmission method over the internet, carrying over 99% of all internet, telephone communication and cable TV traffic.

 

What is Fiber Optics?

A fiber-optic cable is made up of thin strands of glass or plastic known as optical fibers. A cable can have as few as two strands and could increase up to several thousand. Each single strand in the cable is about one tenth of the thickness of human hair. Fiber optic cables carry information using entirely optical technology, meaning that all the data is sent through pulses of light.

Light travels through the fiber optic cable not in a straight line, but by repeatedly bouncing off the walls of the optical fibers. Using common logic, we could conclude that light traveling through a clear glass tube would simply shine through it, however by making the light beam hit the walls of the pipe at a very shallow angle, we cause it to be reflected as if it was a mirror. This is called total internal reflection and is one of the methods used to keep the light from escaping the optical fibers.

Total Internal Reflection

Types of fiber optic cables

There are two types of fiber optic cables: single-mode fiber and multi-mode fiber. Single-mode means the fiber can propagate only one type of light mode at a time. Multi-mode on the other hand, can propagate multiple light modes at the same time. They mainly differ in core diameter, bandwidth, wavelength and required light source.

 

  • Single-mode fiber optic cables usually consist of a single strand of glass fiber which has the diameter of 5-10 microns. It is designed to carry the signal straight down the middle of the fiber without bouncing off the walls, causing the least amount of distortion, allowing it to transmit data over distances up to 100km without needing a repeater. Comparatively to the multimode fiber optic cables, single mode ones also have a higher bandwidth and transmission speeds but require a light source with a much narrower spectral width thus making large scale implementation quite pricey. Despite that, single mode fibers are what is used by the telecommunication companies to transfer data over distances exceeding one kilometer.

 

  • In multimode fiber optic cables, multiple light beams can travel though the core by following different paths. Their fibers have a much larger diameter, usually 50-100 microns and provide high bandwidth at high speeds for medium distance data transmission. The problem arises when the cable length exceeds 900m as the multiple signals transferred through a single fiber over long distances cause distortion, resulting in partial data transmission. They are generally used for local-area networks and can reach up to 100Gbps Ethernet.

 Singlemode vs Multimode Finber Optic Cables

Here’s a table comparing the distances and speeds of the types of fiber optic cables

Cable Type

Fiber Cable Distance

Fast Ethernet 100BA Se-FX

1Gb Ethernet 1000BASE-SX

1Gb Ethernet 1000BASE-LX

10GB Base SE-SR

40Gb Base SR4

100Gb Base SR10

Single mode fiber

OS2

200m

5000m

5000m

10km

-

-

Multimode fiber

OM1

200m

275m

550m (mode conditioning patch cable required)

-

-

-

OM2

200m

550m

-

-

-

OM3

200m

550m

300m

100m

100m

OM4

200m

550m

400m

150m

150m

OM5

200m

550m

300m

400m

400m

 

 

Advantages of Fiber Optic Cables

Fiber optic cables have numerous advantages over traditional copper cabling. Here’s just a few of them:

  • Higher Capacity: The current most widely used copper cable standard, Cat5e supports bandwidth of up to 1Gbps, however fiber optic cables can have bandwidths of up to 100Gbps.
  • Less Signal Boosters: Since light can travel much farther distances down the cable without losing its strength, it minimizes the need for repeaters.
  • Less Interference: A copper cable requires special shielding to avoid electromagnetic interference, which works well most of the times, however it is not sufficient when many cables are strung together. The physical properties of glass in fiber optic cables prevent such issues.

 

What is Dark Fiber?

Although sounding sinister, it simply refers to the fiber optic cables that have been installed but are not currently in use. Extremely large quantities of fiber optic cabling have been laid since the 1980s onward, with the worldwide total being more than hundred million kilometers and some of them still lie unused today. It is generally believed that most networks contain a third to half of dark fiber.