ntt brings fiber-to-the-curb via passive optical networking

ntt brings fiber-to-the-curb via passive optical networking

By ROBERT PEASE

Creating new excitement for proponents of fiber-to-the-curb (fttc) technology, Nippon Telegraph & Telephone Corp. (ntt--Tokyo) is working to connect customers to multiple services through an all-fiber passive optical network (pon) system. ntt`s network, known as the Pi-pon system, is a new optical access system aimed at providing fttc and fiber-to-the-home (ftth) services while efficiently using the wide-bandwidth and cost-performance characteristics of optical fibers.

In 1994, ntt announced a commitment to further development of its end-to-end multimedia optical network by 2010, when it plans to have all 60 million Japanese subscribers covered by the pon system. ntt`s new infrastructure will allow the network to offer customers video applications, Internet access, and other high-bandwidth capabilities.

pon technology is called "passive" because it eliminates the requirement for active electrical devices or power supplies. For example, ntt`s Pi-pon system uses a passive double star topography, in which a passive optical splitter accepts a light signal from an optical line terminal located in a central office, splits the signal into multiple beams, and distributes those beams to optical network units located near subscribers (in an fttc application) or within the subscriber`s premises (for ftth). This contrasts with active double star networks, which typically must use equipment to convert the optical signal to an electrical signal for transmission via copper or coaxial cable to the home or neighborhood distribution unit.

Lucent Technologies (Murray Hill, NJ) will provide pon technology for the ntt access network throughout Japan. As one of several vendors on the project, Lucent will deploy optical networking units and optical line terminals. Lucent, which already has nearly 7000 employees across the Asia/Pacific region, recently expanded its Bell Laboratories presence in Japan to support this and other projects in the Japanese market. The new Bell Labs research and development organization, which will focus on developing prototypes for pon systems, will be located in Makuhari, near Tokyo.

Moving to the home

ntt also is focusing its efforts to bring fiber directly into the business and residential sectors of Japan through evolving ftth technology. According to Eiichi Shimizu, Lucent`s president of global service-provider business in Japan, ntt is leading the way in the deployment and commercialization of pon-based ftth technology. He says ntt customers will soon lead the world in sophisticated communications capabilities in their businesses and homes.

High costs have been a drawback to optical access networks in the past, but it makes sense for ntt to pursue the technology for several reasons. Japan`s dense population makes ftth much more practical, since customers are in close proximity rather than spread over large geographical areas. Contributing to lower costs is that in Japan, distribution cables are strung from poles in the air, enabling easy replacement of metallic cables without the major construction costs associated with digging up underground cables. Lastly, the cost of fiber is on a downward trend. ntt believes the cost of optical access networking materials and equipment will make ftth the most cost-efficient option by the year 2001.

As part of its pursuit of ftth, ntt has teamed with BellSouth (Atlanta, GA) to pool information, industry expertise, and research data to advance the availability and affordability of ftth technology. The two companies will collaborate on a joint research and development project to create common technical specifications for high-speed optical networking systems (see figure.)

As part of the mutual agreement, ntt and BellSouth will contribute their findings to the Full Service Access Network (fsan) initiative, a group of 14 international telecommunications companies working to develop common broadband access system specifications. Any common technical specifications developed through this agreement between ntt and BellSouth will be disseminated through fsan for possible submission to the International Telecommunications Union (itu) as a future standard. fsan members include Bell Canada, BellSouth, BT, Deutsche Telecom, Dutch ptt, France Telecom, gte, Korea Telecom, ntt, sbc, Swisscom, Telefonica, Telstra, and Telecom Italia.

The primary goal of ntt and BellSouth is to create specifications for technology that would allow optical fiber to be installed from the curb into the home to provide high-speed access to communications networks. Recent technological advances and cost reductions have spurred particular interest in Asynchronous Transfer Mode (atm)-pon, which will be a point of emphasis in the ntt/BellSouth collaboration.

BellSouth`s vision for ftth is for customers to be able to purchase communications appliances locally to be used for voice, video, data, or imaging applications. When plugged into the customer`s home telecommunications network, the needed telecommunications would be provisioned automatically and immediately.

The companies will deploy their experimental technology on a limited basis in the course of their research and development. ntt has already deployed narrowband and video distribution ftth and broadband atm-pon systems, and it plans to introduce a fully fsan-compliant atm-pon system in 1999. BellSouth plans to install a "first office application" ftth system using fsan-compliant atm-pon technology next year.

Besides sharing information on access systems, ntt and BellSouth expect to deepen their joint involvement in the development of access system and optical-fiber distribution technology. q