Introduction to 10G PON Technology

Although 10G EPON and 10G GPON standards and industrial chain have yet to mature, and large-scale commercial deployment is some way off, both technologies have attracted great interest from operators building next generation broadband networks. This paper discusses 10G EPON and 10G EPON from a technical point of view, analyzing the progress of their standardization, related technical parameters development of optical fiber and phase-out of copper, and industrial chain process.

Advances in 10G PON Standardization

Standard maturity is a prerequisite for judging whether a technology commercialization. At this stage, many international standardization organizations including IEEE, ITU-T, FSAN, etc, have been working on the standardization of 10G EPON and 10G GPON technology. Because 10G EPON technology start earlier than 10G GPON, the current standardization process of 10G EPON is slightly faster than 10G GPON.

10G EPON standards are mainly defined by the IEEE just as 1G EPON standard. IEEE organization ratified 802.3av—the international 10G EPON standards on September 12, 2009. This standard focuses on researching the physical layer of 10G EPON technology and follows the MPCP protocol of traditional 1G EPON standard. IEEE 802.3av standard increases the upstream and downstream bandwidth. And in order to ensure operators free from damage and successful migration from 1G EPON to 10G EPON, it also defines the 10G EPON ONU standard parameters, which will make it coexisted with 1G EPON ONU in the same ODN network.

Furthermore, IEEE 802.3av standard supports two physical layer parameters. One is asymmetric mode meaning 10G in the downstream direction and 1G in the upstream direction. The other is symmetrical mode, namely operating at 10G data rate in both direction. Asymmetric mode is considered as a transitional form of symmetrical pattern. In the early stage, Asymmetric mode was utilized in circumstance that people have less demand for upstream bandwidth and limited cost. With the development of business and technology progress, it will gradually be developed into a symmetrical mode.

According to ITU-T study plans, NGPON will experience two standard phases. The first phase is XG-PON which coexists with GPON and reuses GPON ODN. This phrases contains two models: asymmetric uplink and downlink XG-PON1 and symmetric XG-PON2. Second stage is NGA2 which completely builds new ODN. The highly concerned Wavelength Division Multiplexing - Passive Optical Network (WDM-PON) technology belongs to the second stage. It achieves the expansion of access network by using multiple wavelengths in a fiber. But brakthrough can’t be made in some difficult technologies, such as in the burst mode CWDM, colorless ONU transceivers, and tunable WDM devices. WDM-PON is still at the proof stage.

In the ITU-T SG 15 plenary session held in the end September, 2009, Q2 Working Group officially launched the first stage text of NG-PON standard namely overall demand (G.987.1) and Physical Layer Specifications (G.987.2) for next-generation PON systems, and also made a program to publish relevant standards about transmission convergence layer (G.987.3) and management control interface (G.988) in mid-2010.

Technical Parameters of 10G PON

Both IEEE 802.3av and ITU-T G.987 protocol suite have made a detailed definition for relevant technical parameters of 10G PON, physical layer index and optical power budget. However, due to different starting points of the two major standards organizations, the technical indicators also exist some differences.

There are four key points of 10G EPON technology:

1.10G EPON defines six optical power budget, in view of the asymmetric mode PRX10, PRX20 and PRX30 as well as for symmetric mode PR10, PR20 and PR30. These six modes of optical power budget model can basically meet the needs of the operators’ network construction.

2.While achieving the forward compatibility with the conventional 1G EPON at multi-point control protocol layer (MPCP), 10G EPON technology also extends the original message type for reporting the switch time of optical terminal equipment (OLT) and ONU to meet the requirements of 10G EPON system.

3.10G EPON uses (255, 223) Forward Error Correction (FEC) encoding method. This code encodes with FEC coding deployed in 1G EPON, but its strong encoding gain can support the lower sensitivity of the optical receiver.

4.10G EPON has re-planned uplink and downlink wavelength. Downlink uses 1268-1280nm wavelength, while uplink then reuses the original wavelength of 1G EPON—1575-1580nm wavelength. In order to avoid wavelength conflicts, 10G EPON uplink can only use time division multiple access (TDMA) manner.

The released G.987.1 standard defined 10G GPON system's overall technical requirements and system architecture, and this standard clearly put forward that the 10G GPON system should fully support the traditional telecom services and all emerging businesses while ensuring good QoS. At the same time, the standard stated that related content , such as dynamic Bandwidth Allocation (DBA) algorithm, energy saving, authentication and encryption, should inherit the original 1G GPON technology. In contrast, the G.987.2 focused on standardizing 10G GPON physical layer parameters, including downlink rate, ODN power budget, splitting ratio, uplink and downlink wavelength range and line coding, etc.. Although uplink and downlink wavelength range of 10G GPON is the same with that of 10G EPON, the uplink and downlink wavelength is not in conflict with 1G GPON. Therefore, 10G GPON uplink and downlink all used wavelength division multiple access (WDMA) manner.

Development of 10G PON Industrial Chain

Usually, a complete PON industrial chain includes three links: chip, optical modules and equipment. If we want to analysis PON industrial chain, we should analysis the developing state and tendency of these three links respectively. At present, 10G EPON and 10G GPON still can't reach the requirements of large-scale commercial applications. Although some equipment manufacturers have recently introduced 10G EPON or 10G GPON products, they are still in testing stage, which isn't reliable enough to use in commercial field.

Conclusion

10G PON technology meets the needs of high-capacity access network as it can increase data rate, support larger split ratio and cover more subscribers. Thus, 10G PON is surely to become the hot technology for telecoms operators to achieve sustainable development of network constructions which boast of high bandwidth and deploy optical optical fibers to replace copper in the future. Under this circumstance, this thesis mainly analyses three expects of 10G PON technology including the standardization of 10G EPON and 10G GPON (two mainstreams of 10G PON), related technical parameters and the development of 10G PON industrial chain.

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