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  • NTT Readies Optical Fiber Network for Connection to Homes
  • July 27, 1998 (TOKYO) -- Nippon Telegraph and Telephone Corp. (NTT) outlined its implementation schedule of fiber-to-the-home (FTTH), which will start between 2001 and 2002, at the earliest.
    NTT is responding to demands of residential users for earlier and more inexpensive optical networks. Their needs for telecommunications services, such as the Internet, are growing.

    The pi System Will Promote FTTH

    NTT started implementation of optical fiber links from telephone stations to poles near each house in Kobe City, Nagoya City and Aomori City in March 1998. This is called the pi System, and it is the initial step toward full realization of FTTH.

    The pi System is not sufficient to realize full FTTH, because it uses conventional copper wire telephone lines from poles to residences (See chart). However, players in the telecommunications industry hope the pi System will help make FTTH a reality.

    Currently, there has been little progress in introducing FTTH due to expensive equipment and components of optical fiber systems. In return, that means there has been no cost reduction of hardware due to delay in introducing FTTH.

    Therefore, the market needs a system for laying and extending optical fiber cables to points near homes before FTTH can come into high demand. The pi System was devised for this purpose.

    There is an underlying reason for this trend. "A key factor is that costs for installing optical fiber cables became almost equal to those for laying copper wires in late-1997," said Akira Hirooka, Optical Access Network Project Manager of NTT Access Network Systems Laboratories.

    He means NTT can also save costs by installing optical fiber cables that have longer life and are less costly compared with copper wires, which might be replaced after 11 years.

    The pi System has a system configuration that enables the sharing of telecommunications equipment among more than one subscriber, which turns out to be a major reason for cost reduction in installation. The system configuration is called passive double star (PDS). It allows 128 subscribers to share one system.

    According to some industry estimates, NTT will have installed pi Systems equivalent to 4-5 million circuits by fiscal 2000. NTT has not revealed specific figures.

    In this deployment, almost 3 million circuits will be constructed every year after fiscal 2000. The massive implementation is expected then to gradually bring about a downward trend in prices of telecommunications equipment and components for optical fiber transmission.

    Authentic FTTH Under Development by Manufacturers

    If a home user requests an extension of an optical fiber cable to his or her residential premise, it can be fulfilled as long as the pi System reaches a pole near that home. But only 10 percent of users now connected to all the circuits can enjoy FTTH services based on the pi System.

    Therefore, so-called "authentic" FTTH is being addressed by manufacturers of telecommunications equipment and optical fibers, meaning that all the households will have a direct optical fiber connection.

    For example, installation costs of FTTH will be reduced to the level of copper wire installation costs in two to three years, according to a researcher at Fujitsu Laboratories Ltd.

    The costs of FTTH can be brought down to match those of copper wire within 1998 or they can be less expensive in the near future, according to a researcher at Matsushita Communication Industrial Co., Ltd. The costs can be reduced along with competition among manufacturers, which would work favorably for NTT's implementation of FTTH between 2001 to 2002.

    There is a consensus among telecommunication equipment manufacturers on the best system configuration for realizing an authentic FTTH: asynchronous transfer mode-passive double star (ATM-PDS). ATM-PDS can provide services for all users in a service area with a transmission rate of a maximum of 156Mbps. This system can meet the needs required for multimedia services.

    However, there are some issues yet to be solved. For instance, current ATM-related equipment is very expensive, since its sales target is telecommunications providers and enterprises with a backbone network system. Some speculate that ATM facilities would cost 1,000 times more than synchronous transfer mode (STM) telecommunications facilities, which have been introduced by NTT.

    In summary, the market still observes unsettled competition between the ATM-PDS technology and the synchronous transfer mode-passive double star (STM-PDS) technology as to which should become the standard system configuration of FTTH.

    Opposition from Domestic Observers to NTT's Policy

    NTT and other manufacturers have not yet obtained full support from those who doubt the success of the scenario for introducing FTTH. It is mainly because prices are too high to practically use FTTH, and the implementation schedule is too slow.

    It is easy to understand why the prices cannot be lowered. The market-oriented principle of competition doesn't exist. Moreover, there is no checking system for NTT's strategy, even if it misses a point.

    "The Telecommunications Business Law should be revised so that carriers other than NTT can provide high-speed services," said Toru Takahashi, chairman of the Internet Association of Japan.

    Another criticism was issued by Takashi Tsutsui of Teikyo University, who said, "The Japanese government should establish a new law with the same legal force as U.S. Telecommunication Act of 1996."

    NTT plans to complete the full deployment of optical communication systems by 2005. That will provide a high-speed service with a maximum performance of 10Mbps based on the pi System. However, there are strong arguments about whether users can really wait for the service until 2005.

    "Asymmetric digital subscriber line (ADSL) technology should be adopted, as it has been already available for commercial use in the United States," said Masataka Ohta of the Computer Center of Tokyo Institute of Technology.

    NTT also has been conducting technical validation tests of ADSL, wireless local loop (WLL) and Multimedia Mobile Access Communication System (MMAC) for application to telecommunications services for home users.

    However, they are still positioned as complements to FTTH.

    The only way to respond to naysayers is for NTT to provide inexpensive high-speed services using FTTH based on ATM-PDS technology.

    Hirooka of NTT commented, "FTTH is the best state-of-the-art technology. No engineers in this field doubt that FTTH can become an ultimate technology in telecommunications engineering."

    Chart: Three Methods to Realize Full Optical Fiber Communication Systems


    NTT's expression, "the realization of optical fiber communication systems in access networks,"
    doesn't simply mean realization of FTTH.
    NTT also includes both the central terminal and remote terminal (CT/RT) method
    as well as the pi System to the category of the realization of optical fiber communication systems.

    (return to news)

    Related story: Electronics Makers Propose Version of ADSL to ITU-Telecom

    (Nikkei Electronics)


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    Updated: Sun Jul 26 18:05:21 1998