Re: FTTH- How / When / Why is it going to happen?
Thread- The following article is almost a summary of the recent conversations we have had here on the LMT. Funny how the article, which I just now read, reflects a lot of our thoughts. I think it reflects Frank's thoughts(but I could be wrong) about network design, and definitely my thoughts about what will drive it to become a reality.
Frank- The technical design comments are near the bottom. You may find those of interest. I can only understand about 3/4th of it. Maybe 1/2?<g> I need to learn more about FTTH and PON. You and ftth have gotten my interest up. Thanks. -MikeM(From Florida)
*****************************
Fiber-to-the-home starts marching to market
High-speed fiber optic connections are already reaching into the home, with the number of connections growing quickly. New products are enabling this growth and may even spur the introduction of metro WDM systems to support it.
By: Neil Savage
June 26, 2000-- The advertisement for Harbor Hills, a new housing community on the Oregon coast, promises all one could want, with spectacular views, peaceful surroundings, and…"ultimate bandwidth"? With the phrase liberally sprinkled in its promotional literature, the community is touting the fact that all its houses are being built with fiber optic cables to link them to high-bandwidth servers, providing optical communications directly into the home at rates up to 1.8 Gb/s.
Meanwhile, in Palo Alto, CA, city officials are recruiting 100 residents for a pilot project to study how fiber-to-the-home (FTTH) connectivity can be achieved. And Bell South (Atlanta) is promoting a program to wire new homes with fiber optic cable so they can simply plug in to an optical network.
High speed to the home
With long-haul networks moving toward an all-optical system and demand for high-bandwidth applications growing, optical components companies say FTTH is the next logical step in bringing consumers high-speed connections, up to 10 Gb/s. Using a transmission system at a central office and a passive optical network running to converter boxes in individual homes, service providers can supply telephone service, high-speed Internet connections, and cable television in a single package.
Already pilot programs are being run and cable is being laid to make the service possible, but analysts say how fast these dreams become reality will depend on both the costs of installing the systems and how much demand there is for the service.
"I think things will happen over a period of time, but not in the next few years," said Claude Romans, director for access networks at market research firm RHK (South San Francisco). "I think it’s getting close, but I think you have to step back and say ‘why do I need this?"
Cost concerns
The basic driver for high-bandwidth home access will be for television, Romans said. With the cost of installing servers and transmission equipment, over and above the cost of wiring homes, it’s not yet clear how profitable such a service would be.
Jeff Montgomery, chairman of market researcher ElectroniCast (San Mateo, CA), agrees that equipment has to become cheaper and a profit model has to be developed. But the market for FTTH is real and growing, he said. ElectroniCast says FTTH systems were in place to serve 73,000 homes in the US last year, although not all homes were actually connected to a service. This year, Montgomery projects, connections will be available to 190,000 homes, with the figure rising to 1.59 million in 2004 and 6.26 million in 2009.
Practical solutions
Optical Solutions (Minneapolis), which makes a FTTH system that links a central office to field splitters capable of serving 32 homes apiece, has 30 providers in various stages of deployment. Some have only recently signed contracts and are studying how to implement the system, but some have actually been deploying it over the last four years. Rural Telephone Service Co. has about 1,500 connections installed in Hill City, KS, Optical Solutions says.
Joe Dooley, director of product marketing, says FTTH is first appearing in new housing developments, where there is little extra cost involved in laying fiber optic cable; areas where competitive local exchange carriers have to put in new infrastructure to compete with companies already serving the market; and places where, for instance, the copper system is unable to handle digital subscriber line (DSL) service, the main competitor to fiber for high-speed Internet access.
The issue for telephone companies and cable systems, Dooley says, is whether installing FTTH systems is the most competitive solution right now, or whether DSL and cable modems, which are still cheaper, is the better choice because they can still handle the demand that exists.
"They want to believe that FTTH is the ultimate solution, and it will be there eventually. They just want to see if it’s ready for prime time now," Dooley said. "We believe it is."
Optical Solutions’ system operates at 1310 nm using a frequency division scheme with an RF modulated analog signal. It has one fiber for downstream traffic and a second coming back from the home. Although it does not use wavelength division multiplexing (WDM), Dooley said the company strongly urges its customers to build a network that will eventually be capable of supporting WDM.
Coming to market
Marconi Communications (Pittsburgh) unveiled its own FTTH system at Supercomm (June 4-8 in Atlanta). The system is being evaluated by Bell Atlantic and will be ready for shipment to customers later this year, says John Gibbs, director of marketing in Marconi’s access systems group. The Marconi WDM-based system uses a 1550-nm signal to the home and a 1310-nm signal returning along the same fiber. It will be easily compatible with metro and long-haul optical networks, Gibbs said.
"For those locations that can get DSL and cable modem the bandwidth they’re getting is going to be adequate for the next two or three years," Gibbs said. But after that, he thinks they’ll start running into limitations that only an optical network can overcome. He imagines a home where a parent in one room is having a video conference for work, while a child in another room is using the same technology to chat with friends, and two other people are watching separate television programs. "You add up all those video channels and that’s 10 Mb right there, and that’s not an unreasonable scenario," he said.
Although an all-optical metro network does not yet exist, the experts insist that’s no impediment to FTTH. Users would have high-bandwidth access to the server providing video, which will be the first driver of FTTH use. And local nodes of FTTH will be a reason to speed up the development of the metro network.
Reducing the cost of FTTH
Reflective MEMS modulators at the end user impress the upstream data string on a diverted portion of downstream power, eliminating the need to house a costly transceiver at each home.
One issue with FTTH is the state of the metro and access infrastructure—FTTH implies a fiber link stretching all the way from the nearest trunk line. Assuming that issue is surmounted, however, a second major concern is cost. A bidirectional FTTH link requires the presence of a transceiver at each home, driving up system cost as well as increasing the complexity of installation. Wayne Knox and colleagues at Bell Laboratories (Murray Hill, NJ) are exploring a very different approach, however, one that would eliminate the need for an upstream transmitter.
MEMS modulators
Knox's system takes advantage of the broad bandwidth afforded by a femtosecond laser to generate as many as 4000 closely-spaced wavelengths between 1.5 and 1.6 µm. In practice, the laser would be located at a controlled environment in the central office. At the home, a splitter divides the optical power—a portion passes to the detector and a portion passes down a fiber length to reflect off of a micro-electromechanical systems (MEMS) based modulator, which impresses the upstream signal on the beam.
The scheme irresistibly brings to mind the image of a Boy Scout signaling his troop in Morse code by reflecting sunlight off of a mirror, but Knox and his crew have demonstrated feasibility, sending signals up to 30 km out and back from the source (central office). Using a MEMS-based modulator makes the proposal economically viable. "The whole idea with MEMS is that it is scalable to very low cost," noted Knox.
High data rate and flexibility
The major cost lies in the fiber deployment. According to Knox, in greenfield locations, deployment of FTTH is cost competitive with twisted pair deployment. "Our system provides T-3 [data rates] to scalably large groups of customers," he said.
With so many wavelengths available, the system could drop 100 channels at each node, perhaps becoming as granular as one wavelength per house, he added, contrasting the approach with that of cable modem, in which speed drops as the number of users rises. "You'd never have to give 45 Mb/s to anyone, because it's your own wavelength. Shared data networks will eventually become as antiquated as a party line."
The approach would also provide carriers with the flexibility to address demands of varied customers. A customer with high capacity demand could swap the MEMS modulator with a distributed feedback (DFB) laser operating at 10 Gb/s. |
