FSAN Initiative brings cost-effective fiber applications closer to homes By ROBERT PEASE

More than two years ago, a group of telecommunications network operators conceived an initiative to create requirements specifications for access systems that would support a full range of narrowband and broadband services (see Lightwave, August 1996, page 54). Since they formed the Full Service Access Network (FSAN) Initiative, these companies have made it their mission to achieve cost-effective deployment of full-access networks.

The FSAN group comprises 14 telecommunications companies, supported by a group of equipment manufacturers (see table). These companies represent a total of more than 310 million operational telephony lines and include most of the world`s early broadband adopters.

"We`re basically a consortium of operators joined together to advance the cause of standards that will eventually lead to fiber-to-the-home," says Ralph Ballart, director of broadcast access for SBC. "The number of operators keeps growing and anyone willing to participate is typically welcomed. We`re not as formal an organization as, say, the ATM Forum, but more of a loose consortium of operators." But telecommunications operators aren`t the only companies involved in FSAN. The expertise and support of the supply side of the market is also critical to the success of the initiative.

"It should be noted that FSAN is not just a lot of operators going off in some crazy direction," says Ballart. "The bulk of the technical contributions are coming from suppliers who are involved in and support the FSAN initiative. That helps enormously to ensure the specifications are effectively implemented."

FSAN proponents also point out that the group is not a standardization activity. Rather, FSAN attempts to incorporate applicable standards where they already exist while simultaneously introducing their specifications into the appropriate standards bodies.

Purpose of FSAN

By researching and introducing the most beneficial requirements specifications, FSAN hopes to significantly advance the cost-effective deployment of full-service access networks. The work of FSAN since 1995 has taken place in three phases.

The first phase was to identify technical and economic barriers to broadband access network introduction and determine the best architectural approach to achieve a network architecture that would best meet the needs of network users. At the Full Service Access Networks Conference in London in June 1996, phase one was completed with an announcement that an Asynchronous Transfer Mode (ATM) Passive Optical Network (APON) was identified as the most promising approach. The APON could support a wide range of fiber-to-the-building, -cabinet, -curb, and -home access network architectures (see Figure).

As fiber moves closer to the home, the overwhelming obstacle continues to be cost. For example, fiber-to-the-home networks require an optical unit at the home. This topology needs to be as inexpensive as possible. The APON system is appealing because it allows the sharing of one central office terminal by a number of homes, thus spreading the cost.

"The specifications aren`t so detailed that you`d get plug-in card capability between different suppliers` equipment," says Ballart. "But once you have a set of common specifications and can allow parts suppliers to make those components in volume, that should drive the cost down in a way that eventually achieves the low-price target for the home optical unit. That`s the basic thought behind what FSAN is doing."

The second phase concentrated on devising a common set of requirements specifications for full-service access networks. Working teams gathered data, and a consensus was achieved and assembled into a set of specifications. These results were presented at the VIII International Workshop on Optical/ Hybrid Access Networks, held in March 1997 in Atlanta, GA. The abstract document that contains the requirements specifications developed by the initiative can be viewed on the FSAN Web site at http://www.labs.bt.com/profsoc/access/.

The third phase of the initiative recognized that further work was required to achieve the necessary level of detail in three areas: optical access network, customer network, and operations, administration, and maintenance. This phase is ongoing as a way to keep the specifications current with new or updated technologies. One example, says Ballart, is in the network-management area. "Network management-related specifications seem to always be done last and, of course, are critical to a successful system," he explains. "I believe FSAN has made significant progress here."

FSAN today

Currently, the focus of FSAN is to accelerate the availability of the equipment it has specified for trials. With this in mind, two chapters were set up to focus on Fiber-to-the-cabinet (FTTCab) and FTTH. The FTTCab chapter concentrates on ways to improve near-term opportunities to use the APON architecture to reach cabinets that serve a few tens or hundreds of customers in conjunction with very-high-speed digital subscriber line transmission over short-haul copper facilities. The FTTH chapter concentrates on extending the APON directly to residential or business customers.

"We expect to start deploying FTTH in new subdivisions, called `greenfield areas,` in the 2001 timeframe, with deployment to business customers starting even sooner," says Dan Spears, director for exploratory development at BellSouth. "The passive nature of the APON brings economic value by enabling us to share the cost of the central office equipment and the optical fiber over multiple customers without requiring active electronics in the outside plant."

The potential for customer self-provision of new services is also expected to be a major advantage. "FTTCab and FTTH are complementary because they both drive up the volume for APONs and drive down the cost," adds Spears, who is also chairman of FSAN`s FTTH chapter. "I believe that this synergy will be key to the successful deployment of APONs in our networks." q