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Optical submarine

telecommunication cables

By : Munish Bansal

Roll No.- 06429

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Contents A brief history

What and where are submarine cables

Laying and maintenance Cables and the environment

Effects of human activities

The future

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Abrief history-1

1840-1850: telegraph cables laid in rivers & harbours; limited

life, improved with use of gutta percha insulation.

1850-1: 1st international telegraph link, England-France, later

cables joined otherEuropean countries & USA with Canada

1884: First underwater telephone cable service from SanFrancisco to Oakland

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Abrief history-2

1956: Invention of repeaters (1940s) & their use in TAT-1,the 1sttrans-Atlantic telephone cable, began era of rapidreliable communications

1986: First international fibre-optic cable joins Belgium &UK

1988: First trans-oceanic fibre-optic system (TAT-8)begins service in the Atlantic

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What and where are submarine

cables?

Early telegraph cable

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Modern submarine cables

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How submarine cables work?

Modern submarine telecommunications cables rely on aproperty of pure glass fibres, whereby light is transmitted byinternal reflection

Because the light signal loses strength en route, repeaters areinstalled along the cable to boost the signal

New systems rely on optical amplifiers glass strandscontaining the element, erbium. Strands are spliced atintervals along a cable & then energized by lasers that causeerbium-doped fibresto lase& boost optical signals

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Atypical submarine cable system

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Cable size

Cables are small; deep-ocean typeswithout protective armour are typically17-20 mm diameter, similar to that of a

garden hose or beer bottle cap Armoured fibre-optic cables may reach50 mm diameter

In contrast, submarine oil/gas pipes reach900 mm diameter, & fishing trawlstypically range over 5,000 50,000 mmwidth

Cable lengths vary; one of the longest isthe SEA-ME-WE 4 system at ~20,000km

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Laying and maintenance

Laying involves:-

Selection of route

Assessment of potential impacts of cable laying on

environment

Full survey of route and its final selection Design cables to meet environmental conditions

Laying of cables

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Cable laying

Purpose built ships accurately place cables on or under the

seabed, guided by the route survey

Shallow water laying may be aided by divers; deep water

laying may involve remotely operated vehicles

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Cables and the environment

Professionally installed fiber-optic cables have a neutral to

benign effect on the marine environment

Their small diameter means that their footprint is small,

especially when compared to submarine pipelines

They are composed of non-toxic materials that are stable insea water

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Effects of human activities

Submarine cables come into increasing contact with other

seabed users especially fishing & shipping industries

~70% of all cable faults are from fishing & anchoring Natural hazards, including current abrasion & earthquakes,

cause ~12% of faults

Most faults occur in water depths less than 200 m & result

mainly from human activities Faults in water deeper than 1000 m result mainly from

natural causes

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Submarine cables and the futureTechnology:

Cable design & operations are constantly evolving. Future

systems are expected to have even greater capacity andreliability

Development of ocean observatories will rely on new cable

technology including attached environmental sensors &

docking modules for submarine survey vehicles todownload data & recharge

Cables, with sensors to detect chemical & physical changes,

are planned for maritime & coastal defenses

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Environment: Cable systems in some regions are likely face more natural

hazards related to changing climate

Climate change may also affect other marine activitiessuch as fishing, with potential impacts on cables

Measures to preserve biodiversity, ecosystems & resourcesvia various protection zones in national waters & highseas, may impinge upon cable passage

The ocean, especially coastal seas, will be subject toincreased human activities such as expansion of renewableenergy schemes

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Thank You