Analysis of PON Technology and FTTH

I. Introduction <?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />

Although ADSL has become the current mainstream broadband access technology, it is incapable of providing high-definition or interactive video services. The bandwidth potential of fiber access is unmatched by other access methods. In the access network environment, replacing copper cables with optical fiber brings a series of benefits: eliminating bottlenecks in the telecommunications network, reducing maintenance costs, facilitating service convergence and the introduction of new services, improving information transmission quality and communication reliability, facilitating future system expansion, and saving construction investment, etc. Major operators attach great importance to the construction of fiber access networks. For example, as early as the late 1990s, Beijing Telecom built 100 new user optical cable rings in the Beijing area, covering most of the Beijing region and basically achieving Fiber-to-the-Building/Curb (FTTB/FTTC) in the Beijing area. Although Fiber-to-the-Home (FTTH) is the fundamental solution for broadband access, large-scale FTTH deployment is not yet economical at the current stage. The current focus is mainly on implementing FTTB/FTTC, with active fiber access (including PDH, ATM, SDH, GE/FE, etc.) as the primary transmission technology, while Passive Optical Network (PON) has begun to be applied. For FTTH, PON will be the most economical and effective technical means.

II. Passive Optical Network (PON)

Compared with active optical access technologies, PON eliminates active equipment between the central office and the user end, resulting in simple maintenance, high reliability, low cost, and savings in fiber resources. It is the main solution for future FTTH. With the gradual reduction in PON costs, PON has not only gained a certain application market in FTTB/FTTC scenarios, but has also made significant progress in developed countries such as Japan in using PON to implement FTTH. Currently, PON technologies mainly include APON, EPON, and GPON, with the primary difference lying in the Layer 2 technology adopted.

APON is a PON technology standardized by ITU and the Full Service Access Network (FSAN) forum in the mid-1990s. At the end of 2001, FSAN renamed APON to BPON. APON has a maximum rate of 622Mbps and uses ATM encapsulation and transmission technology at Layer 2. As a result, it suffers from insufficient bandwidth, technical complexity, high cost, and low efficiency in carrying IP services, and has not achieved market success.

To better adapt to IP services, the Ethernet in the First Mile Alliance (EFMA) proposed EPON technology in early 2001, which replaces ATM with Ethernet at Layer 2. The IEEE 802.3ah working group standardized it. EPON supports symmetric rates of 1.25Gbps, with future upgrades to 10Gbps. EPON products have achieved greater commercial deployment. Due to its perfect combination of Ethernet technology and PON technology, it has become a broadband access technology highly suitable for IP services. EPON systems at Gbit/s rates are also commonly referred to as GE-PON.

While EFMA proposed the EPON concept, FSAN also proposed GPON, which has been standardized by FSAN and ITU. Its technical feature is the use of ITU-T-defined GFP (Generic Framing Procedure) at Layer 2 to encapsulate and map multiple services such as Ethernet, TDM, and ATM. It provides downlink rates of 1.25 and 2.5Gb/s and all standard uplink rates, with powerful OAM capabilities. In terms of high rates and multi-service support, GPON has obvious advantages, but its cost is currently higher than EPON, and product maturity is also inferior to EPON.

III. Development Prospects of FTTH in China

According to forecasts from relevant consulting firms, the global number of FTTH users will reach 8 million in 2005 and 34 million in 2008. According to IDC data, the global FTTH fiber access network market will grow from USD 503 million in 2003 to USD 2.4 billion in 2008, with an average annual growth rate of 37%.

China has begun to promote FTTH/FTTP applications in certain areas, mainly in the following models: First, emerging operators use FTTP to rapidly deploy services in areas with tight duct/fiber resources, such as the Internet cafe streets of Chongqing CNC and Changsha CNC, and the PON community access of Great Wall Broadband; Second, some residential network operators use FTTP to capture the access and user residential network market, and then provide a public access platform for basic service operators; Third, commercial trials driven by the government or equipment manufacturers, such as the FTTH pilot in Wuhan Changfei Apartment, which achieved "Triple Play" for 158 households, of which 110 households used PON access and 48 households used point-to-point MC access, with plans to further expand the trial scale; Fourth, FTTH trials and partial commercial deployment by major operators, such as the EPON testing and FTTH demonstration community construction carried out by Beijing Telecom, and the EPON broadband access trials by Guangzhou Telecom.

Achieving all-fiber FTTH is the development direction of broadband access. However, mainly due to economic reasons, full-scale FTTH deployment is not yet possible. The success of FTTH depends on multiple factors, such as continued declines in equipment prices and deployment costs, more broadband applications driving users to generate higher bandwidth demand, FTTH demonstrating sufficient advantages in competition with other broadband access technologies (such as ADSL2, VDSL, BWA, etc.), and further opening of the telecommunications market as well as strong government policy and economic support, which are also crucial to promoting FTTH development. Over time, the cost of optical fiber cables and optical components has been steadily declining, and advances in various optoelectronic technologies have created conditions for FTTH implementation; demand for new broadband services such as IP TV will further stimulate FTTH development; the increasing burden of maintaining existing copper cable networks is also prompting operators to favor fiber networks; and competitive pressure from emerging operators and other rivals may force traditional telecom operators to implement FTTH ahead of schedule to secure their competitive advantage in the broadband field. Therefore, there is reason to believe that FTTH has broad development prospects.

Since PON is still in the market launch and promotion stage, for FTTC/FTTB, active access remains the primary means of fiber access at the current stage. In commercial buildings, due to the wide variety of service types, integrated fiber access equipment that provides multiple service interfaces is recommended. Typical equipment mainly includes SDH-based Multi-Service Transport Platform (MSTP), and Ethernet or ATM-based multi-service access platforms. MSTP has been favored in recent years due to its good compatibility with traditional operators' SDH networks and has been widely applied.

The 2008 Beijing Olympic Games will be the first truly broadband Olympic Games in history, and broadband access is the foundation for realizing the Broadband Olympics. By the 2008 Olympic Games, fiber will be deployed to all Olympic venues. It is expected that in the Beijing area by then, in addition to Fiber-to-the-Building/Community, fiber will also be extended to some customers' offices and even some homes. Fiber access technologies such as SDH (MSTP), Ethernet, ATM, and PON may all be applied. In particular, with the development of optoelectronic devices and continuously declining prices, the advantages of PON technology will gradually emerge and play an increasingly important role. Although Olympic communications will mainly rely on mature technologies and networks currently deployed on a large scale, and new technologies will not account for a large market share, the business demand of the 2008 Olympic communications itself will have limited pull on the FTTH market. However, since a large number of new technologies will inevitably be adopted during the Olympic Games to showcase the latest achievements in communications development, the 2008 Olympic Games will certainly have a significant incentive and demonstration effect on the application of new broadband technologies such as FTTH in China.