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Laser amplified network sent data over 37 miles along fiber cable

The digital divide in America is significant when comparing the availability of high speed internet access in urban portions of America to those of rural America. The same digital divide exists in many other countries as well and a big push is underway around the world to reduce and eliminate this divide.

Dr. Ka Lun Lee and other researchers at the University of Melbourne and NEC Australia are experimenting with a new way to boost the reach of broadband using existing technologies. The researchers have discovered a method that will be able to cheaply cover 99% of people living within the Victoria province of Australia.

People who live close to cities can choose from DSL and cable broadband sources, but those living in rural areas often only have fixed wireless or satellite broadband to choose from, both of which are less reliable than DSL or cable and cost more. The high cost means that many rural dwellers can’t afford broadband.

The researchers have developed a method to boost the distance that gigabit passive optical networks (GPON), like those used by Verizon's FiOS network, to provide high bit rates over long distances. Lee says that the roughly 19 miles that GPON networks are capable of reaching now would still leave many rural locations in Victoria without coverage. He and his team have conducted experiments using a device called a Raman amplifier to send signals over 37 miles.

The amplifier is a powerful laser that is installed in the central office of a network provider and feeds the optical signal that carries information with energy as it heads out over fiber optic cables. The laser is able to increase the reach of the broadband signal by a factor of close to ten times.

In experiments, the team of researchers was able to build a mock system with a signal transmitter, simulated splitter, and a receiver at the other end. The experimental setup was able to transmit error free data at a speed of 2.5Gb/s over single mode fiber 37 miles long.

Lee estimates that a distance of 37 miles would allow the existing central offices of providers to service 99% of those living within the Victoria province. Not only would rural customers be able to access broadband data speeds, Lee says that the technology could also help urban areas as well.

By increasing the distance that a central station can send data, fewer central offices would be needed and a provider could close some offices and would need less real estate to set up a network.

The new system isn’t without drawbacks though. Lee says that the significantly increased strength of the amplified signal would require additional safety measures and careful inspection of fiber cabling for breaks.

Lee said in a statement, "We have proven that long-reach PON is cost-competitive with other broadband technologies in rural areas and can easily provide much higher access speeds."

Lee believes that this technology could also be used in the U.S. and that the team will be investigating ways to enhance system performance and constructing a prototype network.

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RE: um.. one way
By JoKeRr on 3/18/2009 4:33:01 PM , Rating: 3
Your argument is not necessarily true, since raman pump can be used as co-propagating or counter propagating.

The idea of using a raman pump (based on stimulated raman scattering, which create optical power gain with the phonon vibrations (this is the raman effect part), and the raman effect is induced by the high power narrow spectrum laser, the power loss of that laser create the vibrating phonons) is nothing new, it's been used in long haul DWDM networks, and single stretched span (SSS) submarine networks for a long time, and it's still used today. In some cases of SSS networks you need raman lasers in watts(!!!) as a pump and u can have the signal propagate over 300km without amplification in the link. Overall I'm not that impressed with the result they got, but it is better than the nominal range of GPON, which is ~20km reach. The reach limitation could be due to chromatic dispersion rather than signal power though. In my opinion the biggest reach limitation of GPON is due to the passive power spliter near the residential front, the power is split 32 ways. Not to mention in the downlink & uplink you need to do time division multiplexing. You just can't squeeze out a lot of bandwidth out of GPON.

WDM-PON is a much better solution, you can have symmetric 1gbps bandwidth per user, up to 16 users per fiber, and potentially 32 in the very near future.

"I'm an Internet expert too. It's all right to wire the industrial zone only, but there are many problems if other regions of the North are wired." -- North Korean Supreme Commander Kim Jong-il
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