Links between cities and cables that run alongside roads and into houses and officers are certainly impressive — and without them we wouldn’t have high speed internet. The secret world of submarine cables article tells that Internet’s largest and most important champions are the privately-owned submarine cables that orbit the Earth. The submarine telecommunications industry has deployed the core of the global fiber grid by setting up full duplex telecommunications solutions between continents. Across these cables, which span distances of up to 13,000 km, terabits of information squirt from one side of the planet to another. These fiber optic cables are just three inches thick, and have total capacities of between 40Gbps and 10Tbps. These solutions rely on fiber-optic cables, equipped with high reliability submerged repeaters, which are DC-powered through subsea cable from power feeding equipment in the shore stations.
The generation of submarine fiber-optic cables that revolutionized trans-oceanic telecommunications a decade ago is being retired prematurely. New Life For Undersea Fiber article tells that once the marvel of the telecom world, the first undersea fiber optic cables have reached the point of telecom obsolescence some years ago. The downfall of the first generation of submarine fiber-optic cables was their need for repeaters-devices that boosted the signal strength periodically to enable the information-carrying light waves to span the whole ocean. Early fiber repeaters had to convert faint optical signals to electronic form so they could be amplified, then convert the electrical signals back into light.
In the late 1980s, a new kind of optical fiber was developed that could amplify weak optical signals. An optical fiber amplifier can simultaneously amplify dozens of optical channels since they do not convert each channel into electronic signals separately. Optical fiber amplifier is a section of optical fiber that is doped with a rare-earth element such as erbium or praseodymium and powered with pump laser. Optical fiber amplifier was a huge improvement because it can amplify many signals at different wavelengths at the same time. DWDM is a real boon for oceanic optical fiber cables, allowing the increase of bandwidth without laying new cables undersea. In fact, the utilization of DWDM technology for submarine cable design is trending toward less fiber pairs per cable, significantly reducing the costs associated with intercontinental connections. Many of these use 80 DWDM channels at up to 10 Gbps per fiber pair.
A common sea-going fiber type specification is G.654. Rarely used terrestrially, G.654 fiber is a modified version of the G.652 fiber specification. With G.654, attenuation loss of optical fiber (less than 0.2 dB per km) is reduced to the minimum. Fiber amplifiers still require electrical power, which is fed to them through insulated copper cables, essentially superoceanic electrical extension cables that run down the length of the fiber cable.
Unrepeatered Submarine Fiber Optics Systems represent a new market opportunity for existing and new players in the market. As the technology has developed the capability of unrepeatered undersea fiber optic links continues to increase, opening up new markets where only the cable is placed underwater and the electronics are located in a benign environment on the shore. Unrepeatered systems also require less investment and lower cost for installation and operation. Hence, many smaller players are now able to enter the market. Similar to the repeatered long distance systems, unrepeatered systems are being driven by the unprecedented growth of the internet.
Both old and new ways of sinking a cable into the Pacific, Atlantic, Indian, and even Arctic Oceans requires a billion-dollar logistical feat that requires months or even years to enact. The secret world of submarine cables article has nice map of cables. Read more about optical submarine cables on Wikipedia. Undersea cable system: Technical overview & cost considerations is also good reading.
7 Comments
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Alexander says:
http://sbrouevgleb.blogspot.ru/2015/06/switch-three-qpsk-modulators-twice_25.html
Switch three QPSK modulators twice often and save 50% of power over radio, wire and fiber channels. Switch 15 QPSK modulators 4 often and gain your profit in DWDM systems over ULH market.
A. O. Nekuchaev and S. A. Shuteev
Moscow State University, Moscow, 119991 Russia
e_mail: [email protected]
The idea to use spectral redundancy was patented the Department of Physics, Moscow State University [1]. . The time is divided into cycles, each of which is equal to 2 microcycles. Two wavelengths P11,P12,P13,P14,P21,P22,P23,P24– are called pilots (the duration of each wavelength is equal to one circle) each of which corresponds to a three-bit chip: 000, 001, and so on to 111. First bit is determined by wavelength and second and third by QPSK modulation. Waves S1–S4 are called slaves. Slave Si means that, in a given microcycle, the current symbol is the same as current wavelength with phase i of current microcycle. Every microcycle carries new wavelength with 4 possible phases.
Transmission of the sequence P11–P14, P21–P24correspond to P11,S2,P13,S4,P21,S2,P23,S4.
Transmission of the sequence P11,P11,P11,P11, P21,P21,P21,P21correspond to P11,S1,P11,S1,P21,S1,P23,S1.
Obviously bit rate the same as for three independent QPSK modulators, but power 1.5 times less.
Now let us consider P1i,..,P2i,…,P3i,….P8i (i=1,2,3,4) together 8 different wavelengths and S11(i), S12(i),S21(i),S22(i),S31(i),S32(i),S33(i) together 7 different wavelengths, S1 and S2 are degenerated twice, S3 are degenerated thirdly. Slave Si means that, in a given microcycle, the current symbol is the same as wavelength S microcycles ago with phase i of current microcycle. Altogether there are 8+7=15 different wavelengths. Every pilot carries 3 bits as colour and 2 bits as QPSK, together 5 bits. The cycle is equal 4 microcycles. In any time there are 4 different wavelengths. Every wavelength starts in microcycle and has duration 1 cycle.
During cycle 4*5=20bits with 15 different wavelengths are transmitted in proposed method against 30 bits with 15 different wavelengths as usually. So total capacity will be 6 times with 15 or 90 different wavelengths, which corresponds to 9*(20/30)=6Terabit/sec opposite to 9.0 in usual method, but power will be 15/4=3.75 times less .10lg3.75=5.74dB. Over ULH market and EULH 4 out 15 will be better than 2 out 3, which in turn will be better than existed method.
Usual method
λ 1 λ 2………………………………………………………………………… λ90
Total capacity 9.0Terabit/sec , total power P
New method
λ 1 λ 2………………………………………………………………………… λ90
Total capacity 6.0 Terabit/sec , total power 4P/15
Transmission of the sequence
P11 P12 P13 P14 P21 P22 P23 P24
corresponds to P11 S112 S213 S314 P21 S112 S213 S314
Security of data is 88!=10^134
REFERENCES
1. A. O. Nekuchaev and U. A. S. Yusupaliev, RF Inventor’s Certificate No. 2161374 (MGU, Fizicheskii Fakul’tet, 2004).
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Tomi Engdahl says:
Take a Peek Inside the Undersea Internet Cable
http://interestingengineering.com/video/take-peek-inside-undersea-internet-cable/?utm_content=bufferfdece&utm_medium=social&utm_source=facebook.com&utm_campaign=buffer