FTTH experiences in Japan [Invited]

Transcription

1 Vol. 6, No. 6 / June 2007 / JOURNAL OF OPTICAL NETWORKING 616 FTTH experiences in Japan [Invited] Hiromichi Shinohara NTT Access Network Service Systems Laboratories, NTT Corporation, Hanabatake, Tsukuba, Ibaraki, Japan shino@ansl.ntt.co.jp Received January 17, 2007; revised March 30, 2007; accepted April 1, 2007; published May 8, 2007 Doc. ID Fiber-to-the-home (FTTH) development in Japan is described. Although the title says Japan, the descriptions are primarily from the standpoint of NTT with overviews of the latest Japanese FTTH market trends and discussion of the driving force behind FTTH growth. Also introduced are technologies used to realize the massive FTTH rollout such as FTTH system architecture and easy construction schemes for prompt and massive FTTH service offerings Optical Society of America OCIS codes: , Introduction In Japan, the number of fiber-to-the-home (FTTH) users exceeded in December 2006 [1]. Since 2005, the monthly increase in FTTH user numbers has exceeded that of the asymmetric digital subscriber line (ADSL) user numbers. Many ADSL users are switching from ADSL to FTTH. Recently, the total number of FTTH users outstripped that of ADSL in NTT East. This trend is expected to occur in the whole Japanese market within a couple of years. The Japanese broadband market is entering the full-scale FTTH era. At the initial stage of Japanese FTTH service, FTTH was used only for data service, namely, Internet access. Data speed and price were the competitive issues. Most FTTH providers now use a 1 Gbit/ s Ethernet passive optical network (EPON) system to provide a 100 Mbit/ s interface. It appears that competition based on speed and price has peaked, and the competition is now focusing on services. Currently, high-quality and low-priced IP telephone service on FTTH is spreading rapidly, and triple-play service including broadcast is becoming popular. This paper begins with an overview of the Japanese FTTH market. Second, the FTTH services offered by NTT and typical applications on FTTH services will be addressed. Third, the FTTH systems used to provide these services will be described. Finally, I will introduce lessons learned from actual FTTH rollout and the key technologies used to achieve massive FTTH deployment. 2. Overview of the Japanese FTTH Market The FTTH market in Japan continues to grow rapidly. Figure 1 shows the quarterly net increase in new broadband users in the whole Japanese market [1]. The net increase in new FTTH users outstripped that in ADSL in the first quarter of Since then, the FTTH market has been growing very rapidly, while the ADSL market has been stagnating. Recently, more than 800,000 new users subscribed to FTTH service in each quarter. As a result, the number of FTTH users exceeded in December It should be noted that the number of ADSL users started to decrease in the second quarter of This means that ADSL users started to transfer to FTTH, and their number has decreased to The Japanese broadband access market is indisputably shifting from ADSL to FTTH. The transition from ADSL to FTTH is remarkable in NTT [2]. The monthly net increase in new FTTH users outstripped that in ADSL in November 2004 in NTT East and in June 2005 in NTT West. The number of FTTH users in NTT surpassed in November The number of FTTH users in NTT East overtook that of ADSL in December It is expected that the number of FTTH users in both NTT East and NTT West will outstrip that of ADSL by the end of March The next question is what kinds of users are opting for FTTH. In the Japanese FTTH market, both small and medium enterprise (SME) and residential users sub /07/ /$ Optical Society of America

2 Vol. 6, No. 6 / June 2007 / JOURNAL OF OPTICAL NETWORKING 617 Fig. 1. Quarterly net growth in new broadband users. Fig. 2. Breakdown of FTTH users. scribe to FTTH services. More than 80% of FTTH users are residential users, and the ratio of residential users in FTTH is higher than that in ADSL. This demonstrates that FTTH is accepted not as a luxury service for high-end users but as a service within reach of the general consumer. Figure 2 shows the breakdown of FTTH users. The ratio of multidwelling unit (MDU) users [which includes both (FTTA) fiber-to-theapartment and (FTTB) fiber-to-the-basement installation] in the complete Japanese FTTH market was 60% as of December 2005; the ratio of MDU users in NTT is 40%. The ratio of residents in MDUs is 55% in urban areas, and the average ratio throughout Japan is 40%. This means that FTTH services have been spreading widely to users both in MDUs and in detached houses. In addition to NTT, many players from various industries such as a cable music broadcasting companies, electronic power companies and their subsidiaries, and real estate companies have entered this market. Figure 3 shows the market share of FTTH service as of December Currently, NTT has the largest market share in Japan. It has 67% of the FTTH market and a 76% share of detached houses. As FTTH service becomes more popular, competition between these players will only increase. Fig. 3. Market share of FTTH service.

3 Vol. 6, No. 6 / June 2007 / JOURNAL OF OPTICAL NETWORKING 618 In November 2004, NTT announced its medium-term management strategy. In the announcement, NTT set a target of moving customers to optical access by The question is how to achieve this target. NTT obtained of new FTTH users in the fiscal year (FY) 2005, and it obtained in FY NTT will add new FTTH users each year thereafter, so NTT s total number of FTTH users will reach in Although the target is tough to reach, NTT will achieve these goals by creating attractive applications that are available only on FTTH. 3. Driving Force Behind FTTH Growth The Japanese broadband access market started with ADSL, and ADSL services have been offered extensively since mid ADSL service initially grew at an incredible speed. The number of ADSL users exceeded in December The original peak speed of ADSL was 1.5 Mbit/ s, but ADSL service providers started offering higher-speed ADSL service, such as 12, 24, and 40 Mbit/s, in the past few years. So far, there is no killer application for the higher-speed ADSL service. Strong competition generated by the new players is taken to be the main factor driving the higherspeed service. The new players adopted the strategy of offering higher-speed service in order to dominate the competition. The severe competition caused service speed to become a central issue. Competition for speed in the ADSL market was carried over into the FTTH market. Users seem to select FTTH services because of their desire to use higher-speed and higher-quality Internet access. Higher-speed and higher-quality Internet access has been the key driving force behind the initial growth of FTTH. NTT has been offering four types of FTTH service under the brand name of B-FLET [3]. These are Business service, Basic service for SME and heavy users, Family service for mass users, and Condominium service for MDUs. NTT East and West launched Hyperfamily service and Premium-family service as successors to the Family service in December 2004 and April 2005, respectively. Family service is offered on a broadband passive optical network (BPON) system, while Hyperfamily and Premium are provided by gigabit EPON. The main reason for NTT East and West launching the new services is to meet customer demand for higher-speed service. Currently, Hyperfamily and/or Premium-family and Condominium services are the main FTTH services in NTT. Table 1 shows typical B-FLET applications. NTT is now offering the content service named FLET s square, POD casting, and location free video as well as Web access. FLET s square offers a variety of content such as the Disney channel, on-line games, music clips, sports videos, and cartoons. IP telephone service offered by Internet service providers (ISPs) is also very popular in Japan. This IP telephone service has a specific telephone number of 050-xx...xx, which is different from that of plain-ordinary-telephone service (POTS). NTT East and West started to provide high-quality IP telephone service named Hikari denwa (it means optical telephone) in the spring of NTT is offering Hikari denwa only via FTTH. The main features of Hikari denwa are: Table 1. Typical Applications on B-FLET Transaction Communication Broadcast Internet access a Shopping Trading etc. VOD (IP video) a Flet s square a (content service) Podcasting a Location free video a a Offered by NTT. VoIP b (with a specific telephone number ) Hikari denwa b (High-quality IP phone with ordinary telephone number) Video telephony b rf format c IP broadcast c will be launched in 2008 b Offered by NTT in conjunction with ISP or satellite television provider. c Offered by ISP.

4 Vol. 6, No. 6 / June 2007 / JOURNAL OF OPTICAL NETWORKING 619 Fig. 4. Comparison of fixed monthly charges. (a) The monthly charge of Hikari denwa is cheap. Figure 4 compares the monthly charge of ADSL and FTTH for high-speed Internet access and POTS or Hikari denwa. The FTTH charge differs a little from the ADSL charge. Also, the dialing charge of Hikari denwa is cheap at 8 JPY/3 min. to any fixed telephone in Japan. (b) Hikari denwa has a geographically assigned telephone number. The customer does not have to change his telephone number when transferring from POTS to Hikari denwa. (c) Existing telephone terminals can be used. (d) Voice quality of Hikari denwa is equivalent to that of POTS. (e) Emergency calls such as fire and police can be made with Hikari denwa. Hikari denwa is a very attractive application of B-FLET. The number of Hikaridenwa users is increasing very rapidly. Most newly subscribing users of B-FLET also subscribe to Hikari denwa. Undoubtedly, the driving force behind recent growth of FTTH is Hikari denwa as well as high-speed Internet access. As for video services, video on demand (VOD) is becoming popular in Japan. In April 2006, NTT started to offer a broadcast service on FTTH in conjunction with a satellite television provider. This involves rf overlay. Approximately 300 channels including terrestrial broadcast programs and satellite broadcast programs are being offered. In Japan, analog terrestrial broadcasts will be terminated in There will be areas that will experience poor reception of digital terrestrial broadcasts, namely, the broadcast divide situation. The broadcast service offered by FTTH will eliminate the broadcast divide. Triple-play service including broadcast will be a force driving the full-scale FTTH era. 4. System Architecture Figure 5 illustrates the system configuration for triple-play service in detached houses. The EPON system is being used to offer Hyperfamily and Premium-family services. NTT started offering B-FLET s Family service by using the BPON system and is now introducing EPON on a large scale. Two kinds of gigabit PON systems have been standardized: GPON by ITU-T (G ) and EPON by IEEE (IEEE Fig. 5. System configuration for triple play in a detached house.

5 Vol. 6, No. 6 / June 2007 / JOURNAL OF OPTICAL NETWORKING ah-2004). NTT adopted EPON for gigabit access. The main reasons for this selection are that NTT has a full IP backbone network for B-FLET s services, and now NTT is constructing the next-generation network (NGN). Switches and routers in these networks employ Ethernet interfaces. Namely, network-node interface (NNI) is Ethernet based. As for services, in Japan, high-quality IP telephone and IP data are important basic FTTH services. Business users are also shifting from legacy-leased line service to Ethernet-leased line service. The user-network interfaces (UNI) of these services are also Ethernet based, so there is no need to employ the asynchronous transfer mode (ATM) format. It is clear that EPON well suits the IP network and IP services. In addition, the number of legacy-leased line service users declined to 750,000 in Japan at the end of 2005, and the decline is ongoing. They will account for less than 2% of the FTTH users in Time-division-multiplexing (TDM) emulation technology on Ethernet is also evolving. It is expected that dedicated TDM line service can be offered by EPON. Considering these aspects, we concluded that EPON is the optimal FTTH system for the future. The remaining question was whether EPON could realize sufficient service quality and carrier grade reliability or not. The IEEE standard specifies only media access control and physical layers. To introduce the EPON into the access network, the carrier grade functions such as dynamic bandwidth allocation for fine-grain quality-ofservice control, authentication, and encryption must be implemented. We have realized a carrier-grade EPON system [4,5] that offers sufficient quality and reliability. NTT introduced EPON as a successor to BPON in December We have also achieved interoperability between different vendors optical line terminals (OLTs) and optical network units (ONUs). The transmission wavelengths of EPON are 1.31 m for upstream and 1.49 m for downstream. A 1.55 m cut filter is installed in the ONU in advance for easy and economical video upgrade. The current UNI is 100Base-T, but it can be upgraded to 1000Base-T remotely. Total cost per user strongly depends on the passive optical network (PON) utilization rate. NTT is employing cascade splitting; specifically, NTT installs a 1 4 splitter inside the central office and 1 8 splitters near the customers. This is because singlestage splitting lowers the PON utilization rate given the initial user density, which results in higher costs. Video PON [6] has been used to offer broadcast service. This is a one-way system; the transmission wavelength is 1.55 m as shown in Fig. 6. This system transmits 110 carriers with a bandwidth of 6 MHz. Each carrier can accommodate four to five MPEG-2 standard TV (SDTV) signals or one high-definition TV (HDTV) signal. Therefore, this system can transmit 500 SDTV video signals or 100 HDTV video signals. By employing a three-stage erbium-doped fiber amplifier, one optical modulator can accommodate up to 16,000 ONUs. To improve the transmission quality, we applied an FM-converted scheme [7,8]. The merits of this approach are i. The FM system is robust against reflection, so we can apply super physical contact (SPC) connectors or mechanical splices. There is no need to use angled PC connectors. ii. The FM system has a better loss budget, so the splitting number can be increased, which leads to cost reduction. Fig. 6. System configuration of video PON.

6 Vol. 6, No. 6 / June 2007 / JOURNAL OF OPTICAL NETWORKING 621 Fig. 7. System configuration of B-FLETs in the MDU. iii. The FM system is robust against nonlinear effects and undesired signals. Video overlay can be easily achieved without any video signal deterioration. Also, low isolation WDM filters can be applied, which also leads to cost reduction. ONUs are installed inside houses (Fig. 5). Video ONUs include a WDM filter for video overlay. The TV set is linked to a video ONU with an already installed coaxial cable. The basic video service consisting of terrestrial broadcast channels and satellite broadcast channels can be viewed without a set-top-box (STB). The EPON ONU is connected to the video ONU by a fiber. The EPON ONU is connected to the router by a local area network cable. Wireless telephones are often used as a second telephone and beyond. When the user does not subscribe to broadcast service, the optical fiber coming from the central office is connected to the EPON ONU. Figure 7 illustrates the B-FLET s system configuration in MDUs. NTT has been offering two types of condominium service; one uses category 5 cable and the other uses a very high-speed digital subscriber line (vdsl). In offering these services, the Ethernet point-to-point system, media converter is installed in the basement, namely, FTTB or FTTA. NTT recently started to provide a new type of condominium service, FTTH (Type III in Fig. 7). To provide this service, the EPON ONU is installed in each house, and a 1 32 optical splitter is installed in the basement. FTTH will be the main condominium service because it can offer higher speed and higher quality of service. 5. Easy Construction Technologies FTTH is growing very rapidly in Japan. Creating easy construction technologies and reducing product price are the keys to a successful FTTH rollout. Easy construction technologies enable massive and prompt service offerings as well as low initial costs. NTT East and West are now offering FTTH service to more than 200,000 new users every month. Easy construction technologies are indispensable to offering FTTH service to a great many users. In this section, obstacles to the prompt and massive FTTH service offering and solutions to the obstacles are described. At the early stage of FTTH deployment, obstacles to prompt and massive FTTH service offering are i. It took from a few days to several weeks to fix the service start-up date in reply to the customer s request. This was because network element allocation and manpower allocation adjustment were carried out manually and separately in several divisions. ii. Only fusion splicing was used to connect distribution cable. Fusion splice machines are so expensive that not every working party for service provisioning could have one. As a result, workers often had to wait until one was available. iii. Connecting drop cable to distribution cable and to indoor cable required removal of the cable sheath. It was necessary to set aside a sufficient length of optical fiber for maintenance and reconnection work. The optical fibers had exceeded the

7 Vol. 6, No. 6 / June 2007 / JOURNAL OF OPTICAL NETWORKING 622 length needed for the first connection. The extra bare fiber had to be stored in a cabinet or closure carefully. Excess bare fiber storage work was time consuming and required skills and careful handling. iv. In aerial closures, excess fiber had to be carefully stored in a tray. Because each closure carried a number of fibers, cable connection work was very complicated and time consuming. Moreover, switching work took time. v. In-house optical wiring took time. This is because the optical cord had to be handled with more care than the metallic cord. The minimum allowable bending radius of the optical cord for in-house wiring was 30 mm. It was very difficult to wire the optical cord neatly. Its appearance is unattractive, and there is a possibility of snagging it. To overcome these obstacles, we have developed several solutions: i. NTT has developed an operation support system (OSS) for service offerings that can fix the service start-up date immediately upon the user s request. By inputting customer address and service type, all necessary network elements can be allocated within a minute. Required construction work is also decided. By referring to a manpower database, the start-up date can be determined in a short time. This OSS drastically reduced the time required to fix the service start-up date. The OSS for the service offering is indispensable for a prompt service offering. ii. NTT started to introduce mechanical splicing in addition to fusion splicing for an aerial cable connection. A mechanical splice does not require a power supply, and the assembly tool is cheaper than a fusion splicing machine. Mechanical splicing assembly tools can be distributed to most working parties. As a result, workers do not have to wait for a fusion machine to become available. This makes it possible to deploy FTTH service widely. iii. To eliminate excess bare fiber storage in a cabinet or in an outlet, we have developed a new field assembly connector [9]. This is the cable sheath connector that we call the FA (field-assembly) connector. The connector is so structured that it directly grips the sheath of an indoor or a drop fiber cable. Mechanical splicing technology is applied to allow the simple and reliable assembly of the connector. It can be connected directly with a standard single fiber coupling (SC) connector plug. This connector does not need a special tool, and assembly work is easy. The splicing characteristics are not changed. This connector makes storage much easier, troubleshooting quicker, and cabinets smaller. This connector is being used in cabinets and outlets. iv. To improve the construction efficiency of aerial network connections, we developed a new aerial connector and a new aerial closure: field assembly small-sized (FAS) connector [10] and prefab closure [11]. The FAS connector is almost the same as the FA connector mentioned above. The FAS connector is designed to be smaller than the FA connector so that many FAS connectors can put in the small spaces available in aerial closures. The FAS connector is not compatible with the SC connector. In prefab closures, we employ a preconnected splitter module, patch cord, and FAS connector. All connections are made by connectors, and there is no need to store excess bare fiber. The cable connection work using the FAS connector and prefab closure is very simple and easy. By introducing the FAS connector and prefab closure, construction time can be reduced by 60%. Also, these new technologies make switching work much easier. v. We have realized a freely bendable optical cord. This optical cord shows a negligible loss increase and ensures sufficient reliability, even when the cord is bent at right angles, clinched, bundled, and knotted. This cord is realized by employing a hole-assisted fiber [12]. This optical cord can be wired as easily as metallic wire, and cabling also looks neat. It makes in-house optical cord wiring much easier. A major cause of service failure is the loss increase caused by unusual bending of the optical cord. It is expected that this new optical cord will prevent service outage due to Fig. 8. SC connector with a shutter.

8 Vol. 6, No. 6 / June 2007 / JOURNAL OF OPTICAL NETWORKING 623 unusual fiber bending. To enable the optical cord to be handled by the customer safely and easily, we have also developed an easy-to-handle optical connector. This SC-compatible connector with a shutter mechanism is shown in Fig. 8. When the fiber cord is not in use, the shutter closes to protect the ferrule surface from dust and also to shut off light. When the cord is inserted into a connector, the shutter holder moves back, and the shutter is withdrawn automatically to expose the contact surface. This connector enables do-it-yourself installation. NTT has just started to introduce this optical cord for in-house wiring. These easy construction technologies enable us to offer FTTH service promptly and massively. 6. Summary This paper has offered an overview of the Japanese FTTH market. In Japan, the FTTH market is rapidly growing, while the ADSL market has started to shrink. The Japanese FTTH market was initially focused on high-speed data service, but recently the triple-play service has become the key point of FTTH. Easy construction technologies as well as installed-first-cost reduction technologies are indispensable for offering FTTH service promptly and massively. Accordingly, recent R&D has focused on the establishment of easy construction technologies for massive cost-effective FTTH rollout. To achieve FTTH users by 2010, we have to make further efforts to establish technologies that offer simple and easy use, even though some compromise on performance may be needed. In the full-scale FTTH era, a huge number of FTTH users must be supported efficiently. Therefore, future R&D must focus on operation and maintenance technologies such as remote testing technologies, easy repair technologies, correction technologies, and so on. References 1. (in Japanese) H. Shinohara, Broadband access in Japan: rapidly growing FTTH market, IEEE Commun. Mag. 43, (2005). 4. O. Yoshihara, N. Oota, and N. Miki, Dynamic bandwidth allocation algorithm for GE- PON, in Proceedings of International Conference on Optical Internet (COIN, 2002), pp , paper COIN.MoA1. 5. T. Tatsuta, N. Oota, N. Miki, and K. Kumosaki, Design philosophy and performance of a GE-PON system, J. Opt. Netw. (to be published). 6. S. Ikeda, H. Yoshinaga, and T. Sugawa, Recent FTTH deployment focused on video service of NTT, in Proceedings of the European Conference on Optical Communication (2006), Mo K. Kikushima, C. Kishimoto, S. Ikeda, N. Sakurai, K. Kumozaki, N. Shibata, and T. Sugie, Multicannel analog(am)/digital(64-qam) video transmission equipment employing super wideband FM converter for FTTH, in Proceedings of the European Conference on Optical Communication (1997), pp K. Kikushima, H. Yoshinaga, H. Nakamoto, C. Kishimoto, M. Kawabe, K. Suto, K. Kumozaki, and N. Shibata, A super wideband optical FM modulation scheme for video transmission systems, IEEE J. Sel. Areas Commun. 14, (1996). 9. H. Aoyama, H. Tanaka, Y. Hoshino, and Y. Oda, Optical wiring technology for a serviceready and low cost FTTH service, NTT Tech. Rev. 3, (2005). 10. T. Nakajima, T. Terakawa, M. Toyonaga, and M. Kama, Development of optical connector to achieve large-scale optical network construction, Presented at the 55th International Wire and Cable Symposium, Inc./Focus (IWCS, 2006), pp M. Toyonaga, M. Awamori, H. Tanase, and M. Kama, New aerial optical closure technologies, Presented at the 55th International Wire and Cable Symposium, Inc./Focus (IWCS, 2006), pp K. Nakajima, K. Hogari, J. Zhou, K. Tajima, and I. Sankawa, Hole-assisted fiber design for small bending and splice losses, IEEE Photon. Technol. Lett. 15, (2003).