Section 3 Characteristics of Fiber-Optic Networks This section summarizes the needs and technological trends in info-communications and the future role of info-communications media. The section has been prepared in consideration of new technologies, and discusses the characteristics of the fiber-optic network; the core of future network infrastructure. 1. Overall Trends in Info-Communications 1) Needs a. Required Conditions The demands for more diverse applications and strengthened networks will grow significantly in the society of the early 21st century. Required for the info-communications system are set out below. The way in which info-communications is used will also evolve. Greater reality Many forms of expression combining images and audio will be devised to communicate information with a reality which cannot be conveyed by text alone. Demand for simulated experiences through virtual reality will also increase. Interactivity With a growing information trend towards user preference, systems will need to support free selection from a broader range of options. This will promote a shift from hitherto one-way information distribution media to two-way media. The needs of individuals transmitting information will also increase. More innovative communications Important will become: functions permitting decisions to be made based on recognition of natural language and vaguely uttered key words; functions for assisting people in their information-based activities such as helping them make decisions; and functions which enable action to be taken on the user's behalf. Functions which meet particular individual needs will also become essential. Temporal and geographic expansion Thanks to mobile communications systems, individuals need never be cut off from access to information in any aspect of their lives. The need for a global communications capacity, regardless of time or place, will inevitably arise. Sharing information Functions which allow people to access information on ideas, knowledge and social events whenever they want will assume greater salience. This will require creation of a database of past and present events, and people will have to have free access to that database in terms of time and place. Individuals will be able to exchange information readily. This will promote the creation of "information-oriented communities," which will gradually replace traditional communities. b. Needs and Transmission Capacity Responding to advanced needs in info-communications will require the subscriber system to boost a greater transmission capacity. Business premises Teleconferencing and business LANs will be well established in the business community by about the year 2000. This will necessitate a transmission capacity of some 150 Mbps in general (and 600 Mbps in some business premises). By around 2010, image and data transmission requirements for businesses will expand, and transmission capacity requirements will have increased approximately to about 600 Mbps. Businesses, including research organizations involved in advanced information provision activities, are likely to need a transmission capacity on the level of Giga bps. Households The household interactive transmission capacity is expected to reach about 1.5 Mbps by around the year 2000 as a result of telephone use and the spread of facsimile communications, data communications and multimedia applications. As for video distribution, HDTV and digital TV will have been introduced in addition to conventional TV, creating a demand for high-speed broadband capacity. It is expected that 6 MHz or 27 MHz will be necessary for one analog channel, while 10 to 60 Mbps will be required for one digital channel. By around 2010, Japan will enter the age of interactive image communications in the home, with applications including telecommuting, telemedicine and remote education. This will necessitate broadband transmissions of 10 to 30 Mbps. HDTV will have developed mature applications in terms of video distribution. Wider use of ultra-high-definition and three-dimensional TV is also expected. A 10- to 120-Mbps capacity per channel is expected to be essential for digital systems. Outlook for Applications and Transmission Capacity 2) Technological Development We have witnessed a number of significant developments recently in the technologies fundamental to high-performance info-communications systems, among them basic and application technologies that will contribute to advancing info-communications. This work will eventually result in meeting the needs discussed above. a. Transmission Technologies Wire systems Transit System technologies Transit system technologies currently use an optical transmission of 2.4 Gbps. Commercial testing of optical transmission at 10 Gbps is under way. Research and development of optical soliton transmission and O-FDM (optical frequency division multiplexing) transmission, under which optical signals at different wave lengths are transmitted simultaneously, will enable greater capacity and transmission over longer distances in the future. By the 21st century, optical transmission of Tera bps (about 16 million circuits at 64 kbps) should be possible. Asynchronous transfer mode (ATM) technologies are moving from the test production stage to application. Technologies concerning network management, call control and greater capacity will become available in the future. From around 1995, the service will develop in the sequence of ATM leased line service, ATM switching service and broadband public network using ATM. Subscriber system technologies Among technologies designed for the subscriber system, optical fiber cables comprising 1,000 cores are already in use. Currently under development are 4,000 core cables as well as cables equipped with connectors designed to make connection easier. Technologies of optical amplifiers operating at the 1.55-µm wavelength are nearing completion which amplify optical signals as they attenuate through the optical fiber. Research and development of a 1.3-µm version is under way. A hybrid integrated circuit built by connecting an optical transmitter, optical receiver and electronic circuit is presently in use for electrical-optical converters (E/O) and optical-electrical converters (O/E). However, to achieve dramatic cost as well as size reductions and reliability improvement, a monolithic optical integrated circuit, which can accommodate all of the components on one semiconductor substrate, is being researched. For the CATV network, development of technologies which enable broadband communications having a 5-Gbps capacity (about 1,000 channels on digital compressed images) is nearing completion, thanks to the development of multidigital transmission technologies, including the establishment of broadband communications at about 1 GHz, based on a coaxial system (about 150 channels in analog transmission) and quadrature amplitude modulation (QAM) founded on an optical system. ISDN/C (integrated service digital network for CATV) technologies have already been developed as a way of setting up two-way transmission lines using a CATV network (coaxial). Some of the trunk lines on the CATV network now use fiber optics, and so the requisite technologies are already available. Facilitating the move to multi channel and higher quality communications will require development of a system that includes installation of fiber optics to the subscriber ends, development of digital technologies and the release of more compact and less expensive equipment. Optical subscriber lines should be in widespread use by the year 2000, owing to performance improvement and cost reduction of optical-related equipment, such as subscriber line terminal equipment (SLT), optical network unit (ONU) and O/E, as well as the development of installation and maintenance technologies. Wireless systems Satellite communications and broadcasting technologies Studies on the large-capacity satellite communications, multichannel satellite television broadcasting, broadband satellite HDTV broadcasting and mobile satellite communications using portable terminals and mobile satellite audio broadcasting are in progress. These studies are based on such technological advances as the adoption of broader band, larger capacity and higher power transponders, larger satellite antennae, multibeam, satellite-on-board switching systems and very-small earth stations. Concerning large-capacity satellite communications, broadband technologies have been experimented on using the 900 MHz bandwidth transponders carried on the U.S. R&D satellite ACTS. As for multichannel satellite television broadcasting, a system enabling 150 channels of television broadcasting by two satellites has been developed in the U.S.. Broadband satellite HDTV broadcasting transponders in the 120-MHz bandwidth (about 4.4 times greater than the bandwidth of existing broadcasting satellites) are being developed in Japan. This is to be loaded onto the R&D satellite COMETS, scheduled for launch during fiscal 1996. In the field of mobile satellite communications and broadcasting, researching and developing large antennae, high-power transponders and satellite-on-board switching systems for the next generation's communications and broadcasting needs is being researched and developed in Japan. Furthermore, Japan is examining the functions of mobile communication satellite systems and mobile satellite digital audio broadcasting systems, both of which enable the use of portable terminals. Global mobile satellite communications systems are planned, using many non-geostationary satellites to support portable terminals. The plan includes multi-satellite control technologies and intersatellite communications technologies. Terrestrial broadcasting technologies ISDB (integrated services digital broadcasting) focuses on digital technologies, and has been developed to facilitate simultaneous broadcasting of data, facsimile, video and audio. To help establish ISDB will require further research and development into terrestrial digital transmission system technologies such as orthogonal frequency division multiplexing (OFDM) as well as conditional access technologies for paid broadcasting. Mobile communications technologies Technologies are being developed to establish personal, multimedia and global communications. The goal of creating personal communications has prompted development of technologies to enable the effective use of radio frequencies, including those which permit the use of microcells (with a cell radius of several tens of meters to one hundred meters) and technologies which enable a shift to picocells (with a cell radius of several meters to several tens of meters). Interface technologies operating between wireless and wire systems are also being developed. To promote multimedia, medium- and high-speed (~about 2 Mbps) data communications systems are being developed along with standard protocol to transmit data and video information. The trend toward globalization is encouraging evolution of technologies to achieve international standardization. With an eye toward the year 2000, the goal is to establish a Future Public Land Mobile Telecommunications System (FPLMTS). b. Application and Terminal Technologies New technologies are expected to be in use within a few years in some fields, among them digital compression technology, which aims at improving the video quality to the level of broadcasting standards. Other fields, on the other hand, will require considerably longer before any applications become available. Examples include human-machine interface technologies, such as methods for recognizing handwritten characters and voice recognition systems. An expanded range of technological developments will clearly be necessary in the future. Digital image coding technology The Moving Picture Experts Group (MPEG) 1, based on 1.5-Mbps image coding, as well as H.261, based on such coding systems as video telephone, have already been developed. Standardization of MPEG 2, which is designed to establish a high quality equivalent to that of broadcasting images, including high-definition images, is slated for introduction in late 1994 at the earliest. Development of MPEG 2 equipment should also be completed by end-1994 or shortly thereafter. Concerning these image coding technologies, video-on-demand should find practical application, and multiple access technologies for image databases are expected to be developed. In the future, research and development of high-efficiency coding for creating ultra-high-definition images and high-performance dedicated chips will be necessary. Information storage, retrieval and synthesis technologies Technologies permitting the storage of data on optical disks, magnetic disks and CD-ROMs have already been developed. Overwriting optical disks are effective memory devices that can store large amounts of text and images. Memory devices with a 1-Terabyte (equivalent to 5 million newspaper pages, or 200 movies) capacity have previously been developed. The maximum surface recording density of magnetic disks is expected to exceed 1 Gbit/square inch by around 2000, up from 150 Mbit/square inch at present. Retrieval technologies have benefited from the application of key words. However, to improve the ease of operations, retrieval technologies using figures and images and retrieval based on ambiguous information are being researched. Multi-access and transmission technologies, which are required to ensure that video-on-demand can meet individual demand arising at different times, will be available soon. Multimedia database retrieval (electronic newspapers and electronic libraries) is also likely to be available in a few years, thanks to the development of technologies that enable building of large-memory capacity and retrieval technologies. We will need to research and develop efficient image synthesis technologies including advanced computer graphics technologies. Interface technologies Voice recognition technologies can now permit successful recognition of about 1,000 words when the speaker is identified and about 100 words when the speaker has yet to be identified. Research is being carried out to increase recognizable vocabulary and improve the rate of recognition of unidentified speakers. Handwriting character input technologies are available as of now. Technologies now being developed will reduce restrictions on the number of ways the characters can be written. Image input technologies should advance with research into super-high-resolution charge-coupled device (CCD) image pickup elements. The future will bring demands for development of display technologies to provide larger and more functional displays. Multimedia terminal technologies Personal computers and other equipment have already begun to incorporate multimedia capacity. A multimedia operating system (OS) has recently made its appearance on the market. Development of OS technologies and application programs is needed to facilitate the use of multimedia terminals. More specifically, developing OS, applications and an interface between OS and applications will be required to allow high-speed processing and display of large amounts of information as well as simultaneous display of image, voice and data. Technological Trends for Fiber-Optic Networks and Expected Service Period 3) Info-Communications Media Development a. Characteristics of Info-Communications Media The following summarizes the prominent media characteristics. Characteristics of Info-Communications Media b. The Future of Info-Communications Media Each info-communications medium will be improved and developed in the future in a manner that takes full advantage of its distinguishing characteristics. In the medium to long term, however, it will be necessary to assess the changes in the role of each, taking progress in technological developments and trends in needs into account. Wire systems A wire system has conventionally comprised the core of the analog system telephone network. It has also played the role of the most basic info-communications network. Yet, it has had serious limitations in terms of transmission capacity. The development of optical transmission technologies has enabled a shift to broadband and higher-speed transmission through the wire system. In the intellectually creative society of the future, the fiber-optic network will play a central role as the basic info-communications network. Wireless systems Terrestrial systems Mobile communications are a vital means of responding to the need to communicate at any time from any location. Radio serves as the core of mobile communications. Today, the use of cellular systems is expanding rapidly worldwide. The introduction of the Personal Handy-phone System (PHS) and the integrated worldwide Future Public Land Mobile Telecommunication System (FPLMTS) which is intended to cover data and image transmission will enable mobile communications using radio systems to play a key role as a means for every individual to access information in the 21st century. It is likely that FPLMTS will find greater applications in conjunction with other systems in new fields, such as wireless LAN, contactless IC card systems and vehicle information and communication systems. Fixed radio communications will contribute to improving the reliability of the overall info-communications network, including wire systems, exploiting such advantages as inexpensive construction costs and a strong resistance to breakdowns resulting from damage. They will prove an effective means of installing economical circuits, including subscriber circuits located in sparsely populated areas where demand density is low. Terrestrial broadcasting is playing an important role as a basic medium media. Compared to the cable system, it offers better economy, simultaneous reception capability, and disaster-resistance characteristics. Radio is vital for broadcasting to mobile equipment. Development taking advantage of these features is anticipated in the future. Satellite systems Fixed satellite communications will find applications in counter-disaster wireless communications, where the disaster-resistance capability will be most prominently featured. Also, taking advantage of the features of simultaneous transmission and the flexibility of the circuit set-up, fixed satellite communications will provide large-capacity data and video transmissions that can be conducted from anywhere. They will also be applied to simultaneous, economical communications nationwide. Fixed satellite communications will continue to be utilized as supplementary means of communication, particularly in areas, such as remote islands or mountainous regions, where it is difficult to install wire systems, and they will also offer better reliability to fiber-optic networks. The mobile satellite communications systems capable of using the portable terminals will enable wide-area mobile communications, particularly suitable for mountainous areas or at sea. These mobile satellite communications systems will also support data communications at broader frequency bands than terrestrial radio communications systems. Satellite broadcasting should benefit from the widespread adoption of TV broadcasting by broadcasting satellite and High-Definition Television (HDTV) which achieves higher quality by employing broadband characteristics, as well as the establishment of ISDB and mobile satellite digital audio broadcasting. Regional broadcasting using multiple beams is also expected in the future. Moreover, development of international TV broadcasting, data communications and image distribution using satellites targeting the Asia-Pacific region is expected. 2. Characteristics of Fiber-Optic Networks 1) Broadband, Interactive and Multimedia Capabilities a. Need for Network Enhancement Info-communications networks to support a wide array of activities in the intellectually creative society of the 21st century will need to have broadband, interactive and multimedia communications function so that they can more readily contribute to free information-use activities. The networks will also need to support interactive image transmission and high-speed, large-capacity data communications, and be able to offer multichannel in addition to selective image use and a range of databases. b. Need for Fiber-Optic Networks Image transmission using the asymmetric digital subscriber line (ADSL) system employs conventional telephone lines and permits downstream transmission of about 1.5 Mbps, while the wireless CATV system uses radio to cover areas having a radius of about 10 km. Cost factors make it effective to use these media to provide info-communications in areas where demand is low. However, these functions will be largely fulfilled in the 21st century by digitized fiber-optic networks which provide broadband, interactive communications. Developing diverse applications and terminals to complement the improvements to the fiber-optic networks will also be necessary to achieve this shift. Promoting these concurrently will advance and diversify info-communications media in general because doing so will encourage the advancement of other media, including wireless systems. Compatible policies for wireless system infrastructure improvement will be examined as the fiber-optic networks are improved. 2) Structure of Fiber-optic Networks a. Transit Systems The communications networks have been progressing in a direction exemplified by reduced switching stages, based on improvements in the capacity of switching systems as a result of recent technological innovations and reductions in the per-channel costs of transmission lines. The number of switching stages, which in the case of the analog telephone network was four, has been reduced to two with the digital network. This trend is also expected to continue with the development of the fiber-optic networks. In the transit system, a shift to digitization and the use of fiber optics is currently under way. This trend will accelerate even further in the future. An ATM system which incorporates subscriber switching will be gradually introduced to supplement the current synchronous transfer mode (STM) system. b. Subscriber Systems Even when fiber optics are introduced to the transit system, this alone does not advance user needs. The shift to a fiber-optic subscriber system is vital if users are to be provided with broader-band, interactive and multimedia info-communication functions. Methods of establishing fiber-optic subscriber systems include fiber to the home (FTTH) and fiber to the office (FTTO), where the fiber optics are led directly to each household or company. They also include fiber to the zone (FTTZ), where the fiber optics are used in the vicinity of households (from several tens to several hundred meters away) and metallic or coaxial cables are used to connect optical cables to each household. The subscriber system network structure involves a one-to-one configuration in which accommodating stations and individual subscribers are connected. The current telephone network mainly uses single star (SS) system, in which each subscriber is connected to the respective telephone office point-to-point, while the current CATV system tends to comprise branched or tree systems. Other systems are also available, including passive double star (PDS), where subscriber circuits partially share passive elements, and active double Star (ADS), where subscriber circuits are share active elements in part. These systems are characterized in the following. Characteristics of SS, PDS and ADS Systems 3) Cost Estimates for Building a Fiber-optic Network System The cost of building a fiber-optic network system differs depending on the network structure. Our estimates are based on the following assumptions. a. Assumptions Linkage concept By the year 2010, all business premises and all households will be linked up through a nationwide fiber-optic subscriber system permitting broadband digital communications and multi-channel video transmission. Number of business premises and households The number of business premises in the year 2010 is assumed to be seven million and the number of households 54 million. Number of subscribers in 2010 There will be three subscriptions per business premises and one subscription per household, giving a total of 75 million subscriptions. Unit price for cost estimates The unit price of the equipment will fall because of mass-production economies of scale. We have taken the estimated unit price in the year 2005, which is anticipated to be the average unit price. Network structure The network structure will include the SS system, the PDS system and the ADS system. The video distribution system will include an all-channel transmission system and a selected-channel transmission system. We present two alternative network systems: Case A: Business premises use the SS system and households use the PDS system. Half of all households share an ONU, with one ONU allocated to every two households. The other half of the households use an ONU dedicated to household use. The SS system shall use selective-channel transmission for video while the PDS system shall comprise all-channel transmission. Case B: Business premises and households both use the SS system. Video is transmitted through the selective channel. Overview of the SS and PDS Systems Assumed Transmission Capacity of SS and PDS Systems Used b. Results The following table summarizes the cost results of our estimation: Estimated Cost of Building a Fiber-optic Network to the Year 2010 Estimated Cost of Installing a Subscriber Network Underground Note: On the assumption that existing ones would be used, the above estimate does not include the cost of installing new conduits for feeder lines.