FTTH technology comparison and application strategies of optical fiber access technology

The existing FTTH technology mainly includes the passive optical Network PassiveOpticalNetwork -- PON) Access Technology and the active Switched Optical Network ActiveOptical Network -- AON) access technology. They have their own advantages and are suitable for different application environments. Based on the characteristics of residential districts in China, this paper compares the advantages and disadvantages of the above two FTTH technologies in residential districts in China, and clarifies several outstanding problems of FTTH Access Technology in residential districts in China, talking about the Application strategies of FTTH application technology in China.

1. features of China's FTTH target market

At present, the main target market of FTTH in China is undoubtedly the residents of residential areas in large and small cities. Urban residential areas are generally garden-type residential areas, which are characterized by high household density, A single Garden Residential Area generally has-households, and some even tens of thousands of households. residential areas, including commercial buildings, are generally equipped with communication equipment rooms for installing communication access equipment and line handover for the entire residential area, this configuration is required for telecom operators to compete with each other and comprehensive access to a variety of telecommunication services. The distance between data centers and users is generally less than 1 km; major telecom operators and cable TV operators have already laid 4 to 12 cores in general.) optical cables are routed to data centers in residential areas or commercial buildings; residential communication and CATV access cable Resources in the residential area belong to all operators. Another feature of China's FTTH target market is the existence of industry barriers in the telecom business: telecom operators are not allowed to operate CATV services, and this situation cannot be changed for quite some time in the future.

2. Selection of FTTH Access Technology in China

1) Passive Optical Network PON) problems in FTTH Application in China

Ideal Passive Optical Network-PON) Network structure and distribution, its main characteristics are: Optical Line Terminal-OLT) placed in the telecom operator center machine room, no source Optical Splitter placed Splitter) optical Network Unit-ONU), the Optical Network Unit of the user end ). The distance between the OLT and The ONU is equal to the distance from the telecom operator's central data center to the user. The distance between the OLT and The ONU is similar to the distance from the current fixed telephone access, generally several kilometers, splitter is usually several dozen to several hundred meters away from ONU. The structure and layout of PON highlight the advantages of PON: the entire network from the central data center to the user is a passive network, which greatly saves the optical cable resources from the central data center to the user; this is because the number and size of devices in the central data center are reduced to reduce the number of wiring in the central data center.

Passive Optical Network PON) ideal layout in residential areas: OLT is placed in the center Data Center of telecom operators. Splitter is placed in floor distribution boxes according to the principle that Splitter is as close as possible to users. Obviously, this ideal layout highlights the inherent advantages of PON, but it will inevitably lead to the following problems: first, high-core optical cables are required from the central data center to the residential area, such as 3000 residential areas, in-16-core computing, nearly 200-core optical fiber cables are required. At present, only 4-12 cores are required. It is very difficult to add fiber cables. Second, users are not free to choose carriers, only services provided by a single telecom operator can be selected. It is inevitable that a single operator monopolizes services, which is not conducive to competition among multiple operators and the interests of users cannot be effectively guaranteed. Third, the placement of a non-source optical splitter in a floor distribution box will make the distribution nodes very scattered, making it difficult or even impossible to place the number, maintain, and manage. Fourth, the utilization of network devices and their access ports cannot be improved, because within the coverage of a single PON, the user access rate is hard to reach 100%.

The actual layout of Passive Optical Network PON in residential quarters: OLT and Splitter are both placed in residential data centers. The advantage of this practical layout is that the central data center only needs low-core data cable to the residential area, and the existing optical cable resources can meet the needs. The access lines of the entire residential area are distributed in the residential data center, users are allowed to freely select different telecom carriers. For telecom operators, the network is very easy to place numbers, maintain and manage. Because the access devices and distribution frames are in the same room of the residential area, the Port Utilization of the equipment is undoubtedly significantly improved, the access device can be scaled up gradually based on the number of connected users. However, such a realistic layout also has its obvious disadvantages: first, discarding the PON network structure is the biggest advantage of a passive network, and the network from the central data center to the user network is still an active network. Second, it does not save optical fiber resources because of PON. In addition, PON equipment costs are high and the network structure is complex.

To sum up, there are two conflicting sides in the FTTH application of PON in residential communities: the ideal network structure and layout of PON can certainly exert its original advantages: the entire network from the central data center to the user is a passive network, which greatly saves the cable resources from the central data center to the user, streamlining the number and scale of equipment in the Central Data Center. At the same time, it also brings about almost unacceptable disadvantages: A large number of cable laying lines need to be added; distribution of distribution nodes makes it difficult to place numbers, maintain and manage cables; users cannot freely select operators, which is not conducive to competition among multiple operators and the interests of users cannot be effectively guaranteed; low utilization of network devices and their access ports. However, if PON is used in a residential area, the existing optical fiber resources can meet the needs. The data centers in the residential area are uniformly distributed, which is very easy to place, maintain, and manage, users can freely select carriers to significantly improve the utilization of device ports, but also discard the advantages of PON as a passive network and saving Optical Cable resources, at present, the cost of PON equipment is high, and the network structure is complex.

2) FTTH Access Technology Selection for residential areas in China-point-to-point P2P Access Technology for active Switched Optical Networks in residential areas ActiveOpticalNetwork-AON)

Obviously, the advantages of PON are no longer available in high-density residential areas. Currently, PON technology is not very mature and the device price remains high. We believe that FTTH access is more scientific and feasible because:

Data Centers are generally set up in the residential area;

AON's P2P technology is mature and cost-effective. It can easily provide m or 1g of bandwidth and can be seamlessly connected to existing computer networks;

No need to add optical cables from the central data center to the residential area;

Simple network structure, low construction and operation and maintenance costs;

It is centrally deployed in the residential data center for easy numbering, maintenance, and management;

Allowing users to freely select carriers is conducive to multi-Operator Competition and can be effectively protected by competing user interests;

The port usage of the device is very high, and can be expanded gradually based on the increase in the number of connected users.

The AON-based FTTH Network structure follows the existing low-core optical fiber cables from the telecom operator's central data center to the residential data center. The exchange system is placed in the residential data center, and point-to-point P2P is used from the residential data center to the user end) networking: the access devices and distribution frames are centrally placed in the residential data center. The entire network adopts a mature and low-cost Ethernet protocol. The point-to-point FTTH Network of AON is a widely used FTTH Access Technology in Japan and the United States. More than 5 million of FTTH users on the global 95% line currently use P2P technology with active exchange. Its outstanding advantages include:

High bandwidth: Easy and stable two-way MB broadband access;

It supports Internet broadband access, CATV access, and telephone access to achieve triple play in the access network;

Support for foreseeable new businesses in the future: videophone, VOD, digital cinema, remote office, Online exhibition, TV education, telemedicine, data storage and backup, etc;

The network structure is simple, the technology is mature, and the access cost is low;

Only the residential data center is an active node, and the data center is centrally distributed to reduce maintenance costs and improve the port utilization of equipment;

Allowing users to freely select carriers is conducive to the competition between telecom operators;

This effectively saves Optical Cable resources from the central data center to the residential area, and eliminates the need to add optical cables from the central data center to the residential area.

We believe that the choice of AON Technology for FTTH access is more scientific and feasible, and there is also uncertainty in the Development of PON Standards and Technology:

The standard has just emerged, and multiple versions (EPON & GPON), the standard competition has uncertainty for future promotion.

It takes 3-5 years to standardize and mature related devices. In the next 3-5 years, it is difficult to compete with the current Ethernet P2P devices in terms of cost and popularity.

The cost of PON optoelectronic devices is high: high power, high-speed, and sudden sending and receiving. Currently, the photoelectric devices are far from meeting the requirements of low-cost PON systems.

Currently, the average price of overseas EPON devices is USD.

3. Pay attention to FTTH technical risks and avoid blindly requiring full-service access

Many users require FTTH to support all their businesses and broadband Internet access, cable TV CATV access, and traditional fixed telephone access. This means the three-in-one access, and they hope to implement FTTH access technology in one step. We believe that it is ideal to support broadband Internet access, limited TV CATV access, and ordinary fixed telephone access, but this actually has a huge technical risk.

At present, more than 5 million of FTTH users on the global 97% line only provide Internet broadband access services, because the cost of traditional fixed telephones provided by FTTH is much higher than the technical cost of existing fixed telephones, in addition, there is still a telephone Power Supply Problem in traditional fixed telephones using optical fiber transmission. Although AON, EPON, and GPON all support three-in-one access. However, the EPON and GPON standards have just been promulgated, and it will take a few days for the technology to mature. The two standards of EPON and GPON compete with each other and there will be uncertainty in future promotion, however, the point-to-point passive network structure is not suitable for high-density residential area applications in China. Moreover, EPON and GPON related devices require at least five years of standardization and maturity, in the next five years, it will be difficult to compete with the current cost and popularity of Ethernet P2P devices. At present, optoelectronic devices are far from meeting the requirements of low-cost PON systems. It can be seen that blind pursuit of full-service access using EPON or GPON will inevitably bring huge technical risks.

In the access network, replacement of optical fiber cables with copper cables is an inevitable trend. However, overnight replacement of optical fiber cables with copper cables is impossible for all businesses to access through optical fiber cables. The progress and application of any technology are gradual, and FTTH is no exception. Therefore, in the early stages of FTTH development and promotion, the coexistence of optical fiber and copper cable is inevitable. The coexistence of optical fiber and copper cable can effectively avoid the technical risks of FTTH between users and telecom operators. First, the AON access technology can be used to achieve FTTH broadband access at a low cost in the initial stage, while CATV and traditional fixed telephones still use the same axis and twisted pair wires for access, for villas, CATV access can also be achieved through optical fiber at a low cost without laying the same axis. Second, China's telecom business currently provides industry barriers, and telecom operators are not allowed to operate CATV businesses, on the contrary, CATV operators are not allowed to operate traditional telecom services such as telephones, and the current situation cannot be changed for some time in the future. Therefore, a single carrier cannot provide the three-in-one service on the FTTH access network. Again, because the optical cable can be used for 40 years, and the copper cable is generally used for 10 years, when the communication quality of the copper cable is reduced due to its service life, no additional cables need to be laid. You only need to upgrade the optical fiber equipment, the services provided by the original copper cables can be provided. In fact, as long as the technology is mature and the cost is acceptable, the optical fiber equipment can be upgraded at any time, and the convenience and high bandwidth brought by the new FTTH technology can be enjoyed in a timely manner.

To sum up, optical fiber cables and copper cables are selected to coexist. The FTTH of AON fiber P2P is used to achieve broadband Internet access. CATV and traditional fixed telephones are still connected through the same axis and twisted pair wires, it can effectively avoid FTTH technical risks and enjoy the convenience and high bandwidth brought about by the new FTTH access technology as soon as possible. When the technology is mature, the cost is acceptable, and the industry barriers are eliminated, you can upgrade your optical fiber devices at any time to enable full-service FTTH access.

4. high investment in FTTH Network Construction from a developmental perspective

When we mention optical fiber communication, we often think of its high cost. The subconscious thinks that FTTH Network Construction must be a high investment, but it lacks a rational and developmental perspective to analyze the FTTH investment benefits. This kind of optical fiber network must be a subconscious of high investment mainly manifested in the following: the mistake is that the price of optical fiber cables is high, the construction of optical fiber cables is difficult and the cost is high, and the management and maintenance costs of optical fiber networks will be high in the future, the initial investment in optical fiber networks is high.

Just three years ago, the price of optical fiber cables was indeed more expensive than that of copper cables. But today, with the maturity and popularization of optical fiber production technology, the market price of optical fiber cables per core is only a few cents per meter) the price of copper cables is lower than that of copper cables, and because the materials used to produce optical fiber cables are inexhaustible silica used in nature, their prices will continue to decline over time, copper cables, on the contrary, will rise over time as copper materials are consumed. The times when the price of optical cables is higher than that of copper cables are gone forever.

Undoubtedly, cable laying is more difficult than copper cable construction and the cost is also higher than copper cable, but this is mainly the construction cost. We know that cable laying and erection are labor-intensive work, in the case that China's labor price is very cheap, it is undoubtedly not a prominent problem. Besides, because the cable life can reach 40 years, and the copper cable is generally 10 years, the cable does not need to be replaced or re-laid on a regular basis. From the perspective of development, the cost of laying a single optical cable is undoubtedly far lower than the cost of laying multiple copper cables.

The future maintenance cost of the communication network depends on the reliability and manageability of the network. Because optical fiber communication has a bandwidth that is not subject to electromagnetic interference, the communication content is absolutely confidential, and there is almost no limit, in particular, the reliability of the optical fiber connection head is far higher than that of the copper fiber connection head such as RJ45. These advantages ensure that the FTTH optical fiber network is much more reliable than the network composed of copper cables, while the optical fiber transmission distance is far, with the same physical requirements and network functions, the FTTH optical fiber network connected by broadband must be simpler than the copper network in terms of structure, and the network is undoubtedly easier to manage and maintain. Obviously, in terms of future maintenance and management expenditure, the optical fiber network should be generally lower than the copper network.

As far as the current equipment price is concerned, compared with traditional broadband access technology, the investment in FTTH access network construction is indeed slightly higher at the initial stage, but if the optical cable is depreciated for 40 years when analyzing the investment benefits, FTTH optical fiber networks have lower maintenance and management costs in the future, while FTTH optical fiber networks have higher reliability than copper networks, resulting in higher user access rates, we will find that optical fiber networks have higher investment benefits than copper networks.

It can be seen that it is very important to analyze the FTTH investment benefits from a developmental perspective and scientifically and rationally.

5. Conclusion

So far, FTTH has been widely used in Japan and the United States. There are about 5 million users in the world. China is a developing country, and the consumption level of telecom products is generally low. Currently, very few commercial FTTH users are almost zero.) FTTH is still in its infancy. Therefore, FTTH technology that suits China's national conditions is selected, attaching Importance to the technical risks of FTTH and analyzing FTTH investment benefits from a developmental perspective is crucial to promoting the popularization of FTTH in China.

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