Hello,
Today I'm going to share with you the 10G GPON standardization progress and main content.
(1) Introduction to 10G GPON standard
Since 2004, ITU-T SG15/Q2 began to study and analyze the possibility of evolution from GPON to the next generation PON (collectively referred to as NG PON). In November 2007, Q2 formally confirmed the standardization roadmap of NGPON, and with the goal of "low cost, high capacity, wide coverage, full service, and high interoperability", the research and formulation of the next-generation PON technology standard was rapidly promoted.
NGPON go through two standard stages: one is NG PON1 that coexists with GPON and reuses GPON ODN; the other is NGPON2 that is a completely new ODN. The 10G GPON we usually say belongs to the NG PON1 stage, and the standard number is G.987 series, also known as XG PON. Among them, the asymmetric system (upstream 2.5Gbit/s, downstream 10Gbit/s) is called XG-PON1, and the symmetric system (upstream 10Gbit/s, downstream 10Gbit/s) is called XG-PON2; in addition, ITU-T uses GPON OMCI Based on the expansion, the new standard G.988 (G.OMCI) is formed. The core concept is to integrate all OMCI related documents as the basic standard for terminal management of ITU-T research on optical access systems.
The progress of the G.987 and G.988 series of standards is as follows:
●G.987 Definitions, Abbreviations, and Acronyms.
●G.987.1 General Requirements.
●G.987.2 Physical Media Dependent (PMD) Layer Specification.
●G.987.3 Transmission Convergence (TC) Layer Specification.
●G.988 ONU Management and Control Interface Specification (OMCI).
(2) Main features of XG PON1 PHY layer
Compared with GPON, XG-PON1 has a significant improvement in physical layer requirements.
(3) XG PON1 wavelength planning
The downlink signal band of XG-PON1 is 1575~1580nm (1575~1581nm for outdoor applications), and the uplink signal band is 1260~1280nm. Due to the inevitable coexistence requirements during the evolution of the entire network, XG-PON1 ONUs need to reserve enough bandwidth for existing GPON and CATV signals, and the impact of crosstalk between different signals should be minimized.
The working band of XG-PON1 is called "basic band", and the bandwidth of other system signals is regarded as "enhanced band". For the actual system, the enhanced band includes GPON signals and CATV signals. Among them, the signal wavelength of CATV is consistent with the definition in ITU-T G.983.3. The working band of XG-PON1 is isolated from the enhanced band by a guard band. In order to solve the problem of interference signals, the XGPON1 system uses a wavelength blocking filter (Wavelength Blocking Filter, WBF) on the terminal to obtain better isolation between signals.
(4) Overview of XG PON1 TC layer specification (G.987.3)
G.987.3 has the basic content, mainly including the following aspects:
●The sub-layer structure of the XGTC layer.
●The functions of the service adaptation sublayer include XGEM frame encapsulation, delimitation and data frame segmentation.
●The function of the physical adaptation sublayer, including FEC and line coding.
●The embedded management function of XG PON includes uplink time division multiple access and dynamic bandwidth allocation.
●The physical layer OAM message channel and function of XG PON.
● ONU registration activation process definition.
●XG PON security function mechanism.
● XG PON alarm mechanism and definition.
The XG PON1 TC layer is divided into service adaptation sublayer, framing sublayer and physical layer adaptation sublayer. Refer to Figure below for the layered model.
Conclusion
10G GPON fully consider the compatibility with the original PON system under the same ODN, and have correspondingly enhanced the power budget, wavelength allocation and TC layer functions, and Both asymmetric and symmetric systems are defined.
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