Alcatel (Paris: CGEP.PA and NYSE: ALA), world leader in intelligent optical networking, has successfully achieved a breakthrough in optical long-haul transmission by carrying 32 DWDM (dense wavelength division multiplexing) wavelengths at 40Gbit/s over 2,400km.
This laboratory experiment was made possible by the use of distributed Raman amplification. This technology will represent an alternative solution to traditional repeatered (or erbium doped fiber amplifiers, EDFAs) long-haul transmission by ensuring high-quality transmission and enlarging the amplification bandwidth on long distances. This experiment follows several world firsts achieved by Alcatel in 40Gbit/stransmission (first terrestrial field trial, first 10.2Tbit/s transmission on a single fiber, etc.).
This new world record confirms Alcatel`s breakthrough position in 40Gbit/s development and Raman amplification implementation, as well as its leadership in advanced optical fiber technologies. This result has been obtained by using Alcatel`s 40Gbit/s systems, advanced non-zero dispersion shifted (NZDSF) TeraLight(TM) fiber and full Raman amplification. The latter has been mastered by Alcatel for several years, above all in the unrepeatered submarine domain. Alcatel has successfully extended the principle of this technology to higher bit rates, such as 40Gbit/s, and over long distances.
The distributed or in-line Raman amplification scheme has two potential advantages over the traditional erbium doped amplified solution:
1) Improvement of signal to noise ratio or SNR (ratio between the power of the signal and the noise generated by the transmission, expressed in decibels, required to reach a certain level of signal quality): Raman amplification creates less noise than the EDFAs which is a key advantage for very high bit rate such as 40Gbit/s because, at this capacity, the noise ratio reaches levels that significantly disturb the transmission. At 40Gbit/s, the channels being four times larger than at 10Gbit/s, the noise is proportionally four times higher, so a higher SNR is needed to achieve a correct transmission quality.Thus, longer distances can be reached with the required quality of transmission.
2) Increase of accessible amplification bandwidth: The Raman effect allows for a significantly larger amplification bandwidth than conventional erbium-doped amplifiers, by adding appropriate pumped wavelengths. This further increases system capacity. The other key contributor to the success of this experiment is the innovative fiber arrangement which combines Alcatel`s TeraLight(TM) optical fiber with a prototype "reverse fiber".
This "reverse fiber" has a negative dispersion and a negative slope which exactly compensate the chromatic dispersion of the TeraLight(TM) fiber over a wide spectral range. Together, the fibers complement each other optically to optimize high speed transmission over extremely long distances while avoiding the need for additional dispersion compensating devices. Such an optimal fiber combination ensures high transmission quality of 40Gbit/s optical signals with a high 0.4bit/s/Hz spectral efficiency achieved over long distances.
"This type of capacity has not been achieved to date on this distance, using 40Gbit/s DWDM transmission and a full Raman amplification", said Bernard Le Mou"el, CTO of Alcatel`s Optics Group. "This new breakthrough demonstrates our leading position in optical networking by implementing forward-looking solutions combining our end-to-end optical technologies." Note to the editors Raman amplification: The Raman amplification in an optical fiber stems from the non-linear properties of any other optical fiber: a wavelength sent in the opposing direction of the signal will create an optical gain in the fiber at longer wavelengths. More precisely, the power is shifted from lower to higher wavelengths.
The transmission signal absorbs power from the lower-wavelength Raman pump and is amplified. TeraLight(TM): TeraLight(TM), Alcatel`s Non-Zero-Dispersion Shifted Fiber, is one of the most technically advanced fibers available on the market today. It is optimized for 10Gbit/s and 40Gbit/s operation and offers the ability to operate in all three transmission bands (C,L and the future S band). It can support more than 320 channels at 10Gbit/s and has established a world record for WDM backbone transmission at 40Gbit/s: 10.2Tbit/s over 100 km. This means 160 million voice calls or more than one million high-bit rate ADSL Internet lines could be carried on a single optical fiber.
On May 22, 2001, Alcatel announced two new fibers based on TeraLight(TM) technology: TeraLight Metro for metropolitan networks and TeraLight Ultra for long haul & ultra long haul applications. Both fibers offer cost-effective solutions for operators to upgrade from today`s systems to higher bit rates, to utilize more transmission bands and to increase the number of channels per band.
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Alcatel is the only vendor to master all optical network elements, from optical components, optical fibers and dense wavelength division multiplexing (DWDM) systems to core routers and network intelligence, and from terrestrial to submarine solutions. Alcatel is also the only company to provide both terrestrial and marine services for the installation and maintenance of global, seamless optical networks. According to a 2000 study done by telecom industry analyst RHK, Alcatel holds the number two position in the global optical transport market with 20% market share, distancing itself from all other competitors. RHK also reported that Alcatel reaffirms its number one position in submarine networks with 41% worldwide market share. Moreover, Alcatel claims to be the world leader in total terrestrial and submarine DWDM systems, in digital cross-connects, which contain the enabling technology for operators to offer high bandwidth services, and in synchronous digital hierarchy (SDH) networks. Alcatel`s optics business comprises terrestrial and submarine transmission systems, fiber optics and optical components.
Alcatel has launched a new class of Alcatel stock which is intended to track the performance of Alcatel Optronics, the Company`s optical component business. Alcatel builds next generation networks, delivering integrated end-to-end voice and data networking solutions to established and new carriers, as well as enterprises and consumers worldwide. With sales of EURO 31 billion in 2000 and 110,000 employees, Alcatel operates in more than 130 countries
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