Overview of PON Network

PON has now became a popular network technology all over the globe. It first came in to being in 1995. The International Telecommunication Union (ITU) standardized two initial generations of PON – APON and BPON. And the advancement of PON network has never stopped. Until now, the recent PON standard of NG-PON2 has been put forward in 2015. With the maturity of PON, people are more easily accessible to networks today. But what does PON exactly mean? What’s the composition of PON network? The following part will give you the answer.

PON, also known as passive optical network, is a technology in telecommunication that implements a point-to-multipoint (P2MP) architecture. Unpowered fiber optic splitters are used to enable a single optical fiber to serve multiple end-points such as customers instead of providing individual fibers between the central office (hub) and customer. According to different terminations of PON, the network system can be divided into fiber-to-the-home (FTTH), fiber-to-the-curb (FTTC), fiber-to-the-curb (FTTB), etc. To be specific, a PON is made up of an optical line terminal (OLT) at the service provider’s hub and a number of optical network units (ONUs) or optical network terminals (ONTs) near end users. And “passive” is just used to describe that no power requirement or active electronic component is included for transmitting signals in the system.

PON

Here are some types of PON that have been used throughout the years:

1) APON

Its full name is asynchronous transfer mode (ATM) passive optical network. As the original PON system, APON uses ATM technology to transfer data in packets or cells of a fixed size. In APON, downstream transmission is a continuous ATM stream at a bit rate of 155 Mbps or 622 Mbps. Upstream transmission is in the form of bursts of ATM cells at 155 Mbps.

2) BPON

BPON, also known as broadband PON, is the improved version of APON. It adopts wavelength division multiplexing (WDM) for downstream transmission with the transmission rate up to 622 Mbps. It also provides multiple broadband services such as ATM, Ethernet access and video distribution. Today, BPON is more popular than APON.

3) EPON

EPON or Ethernet PON uses the Ethernet packets instead of ATM cells. Upstream and downstream rates of EPON are able to achieve up to 10 Gbps. It is now widely applied to FTTP or FTTH architecture to serve multiple users. With the advantages of scalability, simplicity, multicast convenience and capability of providing full service access, many Asian areas adopt EPON for their networks.

4) GPON

Gigabit PON is the development of BPON. It supports various transmission rates with the same protocol. The maximum data rate of downstream is 2.5 Gbps and upstream is 1.25 Gbps. It is also widely used for FTTH networks. But compared with EPON, its burst sizes and physical layer overhead are smaller.

Advantages of PON
  • Low cost, simple maintenance, flexible extensibility and easy to upgrade. And no need for power during transmission saves a lot for long-term management.
  • Using pure media network avoids the interference of lightning and electromagnetism. Thus PON network is suitable for areas under harsh conditions.
  • Low occupancy of central office resources, low initial investment and high rate of return.
  • As the P2MP network, PON is able to provide a large range of service to plenty of users.
Conclusion

PON network is for sure an effective solution for multiple network users. EPON and GPON are the most commonly deployed PON systems at present. Since people have been seeking for higher bandwidth provisioning, the capability of transmission will be greatly improved in the near future.

Comparison Between EPON and GPON

PON is the abbreviation of passive optical network, which only uses fiber and passive components like splitters and combiners. EPON (Ethernet PON) and GPON (Gigabit PON) are the most important versions of passive optical networks, widely used for Internet access, voice over Internet protocol (VoIP), and digital TV delivery in metropolitan areas. Today we are going to talk about the differences between them.

PON network

Technology Comparison

EPON is based on the Ethernet standard 802.3 that can support the speed of 1.25 Gbit/s in both the downstream and upstream directions. It is well-known as the solution for the “first mile” optical access network. While GPON, based on Gigabit technology, is designated as ITU-T G.983 which can provide for 622 Mbit/s downstream and 155 Mbit/s upstream. GPON is an important approach to enable full service access network. Its requirements were set force by the Full Service Access Network (FASN) group, which was later adopted by ITU-T as the G.984.x standards–an addition to ITU-T recommendation, G.983, which details broadband PON (BPON).

As the parts of PON, they have something in common. For example, they both can be accepted as international standards, cover the same network topology methods and FTTx applications, and use WDM (wavelength-division multiplexing) with the same optical frequencies as each other with a third party wavelength; and provide triple-play, Internet Protocol TV (IPTV) and cable TV (CATV) video services.

Costs Comparison

No matter in a GPON or in an EPON, the optical line terminal (OLT), optical network unit (ONU) and optical distribution network (ODN) are the indispensable parts, which are the decisive factor of the costs of GPON and EPON deployments.

The cost of OLT and ONT is influenced by the ASIC (application specific integrated circuit) and optic module. Recently, the chipsets of GPON are mostly based on FPGA (field-programmable gate array), which is more expensive than the EPON MAC layer ASIC. On the other hand, the optic module’s price of GPON is also higher than EPON’s. When GPON reaches deployment stage, the estimated cost of a GPON OLT is 1.5 to 2 times higher than an EPON OLT, and the estimated cost of a GPON ONT will be 1.2 to 1.5 times higher than an EPON ONT.

We all know that the ODN is made up of fiber cable, cabinet, optical splitter, connector, and etc. In the case of transmitting signals to the same number of users, the cost of EPON and GPON would be the same.

Summary

Nowadays, since many experts have different opinions on GPON and EPON. Thus, there is no absolute answer to determine which is better. But one thing is clear: PON, which possesses the low cost of passive components, has made great strides driven by the growing demand for faster Internet service and more video. Also, fiber deployments will continue expanding at the expense of copper, as consumer demands for “triple-play” (video, voice and data) grow.

Originally published at http://www.chinacablesbuy.com/comparison-between-epon-and-gpon.html

EPON VS GPON

A passive optical network (PON) is a fiber network that only uses fiber and passive components like splitters and combiners. It starts from the optical line terminal (OLT) in the central office and ends at the optical network unit (ONU) at the customer’s home (as shown in the following figure).

PON

Ethernet passive optical network (EPON) and gigabit passive optical network (GPON) are two popular versions of PONs. The most dramatic distinction between EPON and GPON is a marked difference in architectural approach. EPON employs a single Layer 2 network that uses Internet Protocol (IP) to carry data, voice, and video. While GPON provides three Layer 2 networks: ATM for voice, Ethernet for data and proprietary encapsulation for voice. Moreover, they also vary from each other in terms of bandwidth, per-subscriber cost, efficiency, management system and encryption.

  • Usable Bandwidth

EPON generally delivers 1 Gbit/s symmetrical bandwidth. And its Gigabit Ethernet service actually constitutes 1 Gbit/s of bandwidth for data and 250 Mbit/s of bandwidth for encoding. GPON, however, promises 1.25 Gbit/s or 2.5 Gbit/s downstream and upstream bandwidths scalable from 155 Mbit/s to 2.5 Gbit/s.

  • Per-subscriber Costs

EPON lowers the costs of subscribers by allowing carriers to simplify their networks and to eliminate complex and expensive asynchronous transfer mode (ATM). While the costs of EPON equipment are approximately 10 percent of the costs of GPON equipment.

  • Efficiency

According to the IEEE 802.3 protocol for Ethernet, data transmission occurs in variable-length packets of up to 1518 bytes in EPON. The use of variable-length packets makes Ethernet to carry IP traffic, which significantly reduces the overhead relative to ATM.

In GPON, data transmission occurs in fixed-length 53 byte cells as specified by the ATM protocol. This format makes it inefficient for GPON to carry traffic formatted according to IP, which calls for data to be segmented into variable-length packets of up to 65,535 bytes. This process is time-consuming and complicated.

  • Management systems

EPON requires one single management system, which means EPON results in a significantly lower total cost of ownership. In addition, it does not require multi-protocol conversions, and the result is a lower cost of silicon. In GPON, there are three management systems for the three Layer protocols. Thus it is more expensive. Furthermore, GPON does not support multi-cast services. This makes support for IP video more bandwidth-consuming.

  • Encryption

EPON uses an advanced encryption standard (AES) based mechanism, which is supported by multiple silicon vendors and deployed in the field. Furthermore, EPON encryption is both downstream and upstream. While the encryption in the GPON is part of the International Telecommunication Union (ITU) standard and GPON encryption is downstream only.

All in all, both EPON and GPON have their advantages and disadvantages. It is hard to say which one will be prevailing. But one thing is clear: PON deployment will continue expanding. Fiberstore launches a series of integrated, high reliability and affordable EPON/GPON system solutions for its customers to meet the fast growing demand of PON deployment.

The Application of TDM-PON And WDM-PON

1. Instruction
The bandwidth requirements of the telecommunication network users increased rapidly during the recent years. The emerging optical access network must provide the bandwidth demand for each user as well as support high data rate, broadband multiple services and flexible communications for various end-users. Being considered as a promising access network solution due to the high bandwidth provision and the low operation and maintenance cost, passive optical networks (PONs) represent one of the most attractive access network solutions. TDM and WDM techniques are employed in the PON for higher resource efficiency and capacity, which results in TDM-PON and WDM-PON respectively. TDM-PON provides much higher bandwidth for data application but it has limited availability to end-users. WDM PON can solve the problems encountered in TDM-PON by allocating a specified wavelength to each subscriber. This provides a separate, secure P2P, and high data-rate channel between each subscriber and the CO. This article is mainly written to give you a overview of the application of TDM-PON and WDM-PON as well as the joint application—TWDM PON.

2. Application of TDM-PON
TDM-PON types include ATM PON (APON), Broadband PON (BPON), Ethernet PON (EPON), Gigabit PON (GPON). Now EPON and GPON are extensively used in the telecommunication networks.

2.1 Application of EPON
Ethernet PON (EPON) is a PON-based network that carries data traffic encapsulated in Ethernet frames (defined in the IEEE 802.3 standard). A typical EPON system consists of three components: optical line terminal (OLT), optical network unit (ONU), and optical distribution network (ODN). Utilizing PON topological structure to achieve the access of Ethernet, EPON is equipped with the dual advantages of PON and Ethernet including low cost, high bandwidth, strong scalability, excellent compatibility with Ethernet to facilitate network management, etc. Based on where ONUs are deployed, EPON application mode can be fiber to the curb (FTTC), fiber to the building (FTTB), and fiber to the home (FTTH), as shown in Figure 1.

Application of EPON in FTTB, FTTC and FTTH

Figure 1: The application of EPON in FTTB, FTTC and FTTH

In a FTTC system, ONUs are deployed at roadside or beside the junction boxes of telegraph poles. Usually, twisted-pair copper wires are used to connect the ONUs to each user, and coaxial cables are used to transmit broadband graphic services. Currently, the FTTC technology is the most practical and economical Optical Access Network (OAN) solution for providing narrow-band services below 2 Mbps. For services integrating narrowband and broadband services, however, FTTC is not the ideal solution.

In a FTTB system, ONUs are deployed within buildings, with the optical fibers led into user homes through ADSL lines, cables, or LANs. Compared with FTTC, FTTB has a higher usage of optical fiber and therefore is more suitable for user communities that need narrowband/broadband integrated services.

In a FTTH system, ONUs are deployed in user offices or homes to implement a fully transparent optical network, with the ONUs independent of the transmission mode, bandwidth, wavelength, and transmission technology. Therefore, FTTH is ideal for the long term development of optical access networks.

2.2 Application of GPON
Gigabit PON (GPON) is the far-most advanced PON solution used by European and US providers. It is somehow based on the former ATM access networks (APON, BPON), but GPON’s data encapsulation (GEM) is more generic, and accepts different network protocols, such as ATM, Ethernet and IP. A traditional GPON system is made up of three parts: optical line terminal (OLT), optical network terminal (ONT) or ONU, and optical distribution network (ODU) composed of SM fiber and splitter. GPON possess the advantages of high bandwidth, high efficiency, large coverage, abundant user interfaces, etc. In the access network, GPON can be used to fiber to the building (FTTB), fiber to the curb (FTTC), and fiber to the home (FTTH), as shown in Figure 2.

GPON-application

Figure 2: The application of GPON in FTTB, FTTC and FTTH

In a FTTB system, ONTs are deployed within buildings. GPON can be used to serve for the users of multi-dwelling units (MDU) as well as business users. When serving for MDU users, the services supported by GPON contains asymmetric broadband services (digital broadcast, VOD, IP TV) and symmetric broadband services (content broadcast, e-mail, remote diagnose). When serving for business users, the services supported by GPON are symmetric services (group software, content broadcast, e-mail). Facing diverse services, GPON must flexibly provide private line service at different rate.

In a FTTC system, ONTs are deployed at roadside or beside the junction boxes of telegraph poles. The services supported by GPON consists of asymmetric services ( digital broadcast, VOD, IP TV, files downloading, online games) and symmetric services (content broadcast, e-mail, files interaction, remote education). In addition, GPON supported the expansion of the dedicated line POTS and ISDN.

In a FTTH system, ONTs are deployed in user offices or homes. GPON supports the asymmetric services and symmetric services. The asymmetric services include data broadcast, VOD, IP TV, files downloading, etc. The symmetric services include content broadcast, e-mail, files interaction, remote education, remote diagnose, online games, etc. What’s more, GPON supported the expansion of the dedicated line POTS and ISDN.

3. Application of WDM-PON
As the new-generation access network, WDM-PON makes it possible to transmit multiple wavelengths instead of one wavelength in the PON over the same fiber, thus greatly meet the bandwidth requirements of users. In addition to its efficient use of wavelengths, the WDM-PON also has advantages in its use of optical-transmission power. The network management is much simpler than a TDM-PON, and all future services can be delivered over a single network platform.

WDM-PON can be directly used to achieve FTTC, FTTB and FTTH (see Figure 3) and provide services for business subscribers, the single-family subscribers, the multi-family subscribers and other types subscribers at the same time. WDM-PON offer abundant bandwidth to better meet the bandwidth requirements of the back transmission of 3G and LTE base station, thus becoming the optimal technology for the back transmission of mobile station. WDM-PON also can be used to support reach extension and the transition of existing EPON networks to improve the scalability as well as protect the existing network investment. What’s more WDM-PON can also be adpoted to build the hybrid WDM-TDM PON which combines the dual advantages of TDM-PON and WDM-PON with TDM-PON to be better applied in the optical communication network and provide better services for subscribers. WDM-PON is very suitable for the application environment of telecommunication.

WDM-PON application

Figure 3: The application of WDM-PON in FTTC, FTTB and FTTH

4.Joint Application of TDM-PON and WDM-PON
The combination of TDM and WDM in a PON network could be the most cost effective way of introducing TDM/WDM PON into the access network, which brings TWDM-PON into being. Figure 4 shows the architecture of TWDM-PON . Four XG-PONs are stacked by using four pairs of wavelengths {(λ1, λ5), (λ2, λ6), (λ3, λ7), (λ4, λ8)}. For simple network deployment and inventory management purposes, the ONUs use colorless tunable transmitters and receivers. The transmitter is tunable to any of the upstream wavelengths, while the receiver can tune to any of the downstream ones. To achieve a power budget higher than that of XG-PON1, optical amplifiers are employed at the OLT side to boost the downstream signals as well as to pre-amplify the upstream signals. ODN remains passive since both the optical amplifier and WDM Mux/DeMux are placed at the OLT side. Taking the advantages of TDM-PON and WDM-PON and overcoming their shortcomings, TWDM-OPN can provide higher rates and bandwidth to better serve users.

TWDM-PON architecture

Figure 4: The network architecture of TWDM-PON

TWDM-PONcould be applied in the following ways. The first one to consider is used for pay-as-you-grow provisioning. The TWDM-PON system could be deployed by starting with a single wavelength pair. It could be upgraded by adding new wavelength pairs to increase the system capacity. In this way, the operators can address the bandwidth growth demand by investing what is needed and expanding the future demand. Another application of TWDM-PON is for local loop unbundling (LLU). A TWDM-PON with multiple OLT arrangement is shown in Figure 5 for LLU. Each operator would have their own OLT, each of which would contain some set of wavelength channels. A wavelength-selective device would be used to multiplex the OLT ports onto a single fiber. The wavelength-selective device could be as simple as a filter-based demultiplexer, or it could be an arrayed waveguide router type of device. This scheme unbundles the shared infrastructure for multiple operators. It also offers the possibility of every operator’s OLT being the same (containing all the wavelengths), and a single operator could add OLT resources as they want. What’s more, TWDM-PON can applied in the above-mentioned ways of TDM-PON and WDM-PON being applied.

TWDM-PON application for LLU

Figure 5: The application of TWDM-PON for LLU

5.Conclusion
TDM-PON and WDM-PON, as the popular optical access network , are extensively used in the communication networks. WDM-PON solves the problems of limited bandwidth to each subscriber, high transmission power and poor network security exsiting in TDM-PON, becoming the new-generation access network. However, the cost WDM-PON components are relatively high, which lessen its population. Nowadays the high-speed broadband penetration and ongoing growth of the Internet traffic among customers have been placing a huge bandwidth demand on the telecommunication network. TWDM-PON, combining the advantages of TDM-PON and WDM-PON, comes into being to become the far-most advanced PON. Being able to provide higher bandwidth, higher rates in downstream and upstream and competitive cost, TWDM-PON will plays a key role in the optical communication networks.