Continued… Part V– Comparing Old & New + How Submarine Cables Work

Yesterday I discuss on the comparison of the components/materials used to construct the submarine telecommunications cable between the early days and present (modern days).

Today, I’ll further compare the capacity between the early days and present (modern days) submarine telecommunications cable system in its respective era as follows:

Old Cable Systems:

  • 1866: First trans-Atlantic cable carried telegraph messages at 7 words a minute & cost £20 for 20 word message
  • 1948: Telegram costs reduced to 4 pence a word for transmission across the Atlantic
  • 1956: First trans-Atlantic telephone cable (TAT-1) initially had capacity of 36 telephone calls at a time; calls costing US$12 for first 3 minutes

Modern Cable Systems:

  • 1988: First Atlantic fiber-optic cable, TAT-8, had capacity for 40,000 simultaneous phone calls, 10 times that of the last copper cable
  • Today: Each fiber pair within a cable has the capacity to carry digitized information (including video) that is equivalent to 150,000,000 simultaneous phone calls. Wow!

Knowing that the modern days sub-cables deliver the data much significantly than early days, we may wonder how these submarine cables work.

How Submarine Cables Work

  • Modern submarine telecommunications cables rely on a property of pure glass fibers, whereby light is
    transmitted by internal reflection
  • Because the light signal loses strength en route, repeaters are installed along the cable to boost the signal
  • New systems rely on optical amplifiers – glass strands containing the element, erbium. Strands are spliced at intervals along a cable & then energized by lasers that cause erbium-doped fibers to “lase” & boost optical signals

Based on the above, a typical submarine cable system is depicted on the following diagram.

Typical Submarine Cable System

Typical Submarine Cable System

>> Follow the following link to download free a bigger image size (960×703):

(File Name: )

Source: International Cable Protection Committee Ltd

To be continued… Part VI– Cable Size and Comparing Submarine Cables vs Satellite.


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