Hello, everyone!
Today I'm going to share with you the development of 10G EPON.
Abstract
IEEE and ITU-T initiated research on the next-generation PON standard in 2004 and 2005, respectively. Up to now, the main standards of 10G EPON and 10G GPON have either been officially released or basically finalized, which will certainly speed up the process of device vendors and equipment vendors launching commercial products. This article introduces the main content and latest developments of 10G EPON and 10G GPON standardization.
Introduction
In recent years, with the rapid development of the global broadband access market and the development of full-service operations, the existing PON technical standards have faced challenges in terms of bandwidth requirements, business support capabilities, and performance improvements of access node equipment and supporting equipment. New upgrade requirements. IEEE and ITU-T initiated research on the next-generation PON standard in 2004 and 2005, respectively. Up to now, the main standards of 10G EPON and 10G GPON have either been officially released or basically finalized, which will certainly speed up the process of device vendors and equipment vendors launching commercial products. This article will introduce in detail the main content and latest development of the existing standards of 10G EPON.
10G EPON standardization progress and main content
(1) Introduction to 10G EPON standard
Beginning in 2005, IEEE began to conduct research and standardization of 10G EPON technology, and made breakthrough progress; in September 2009, the standard was officially released (standard number is IEEE 802.3av). IEEE 802.3av specifies two rate modes: 10Gbit/s downlink and 1Gbit/s uplink asymmetric mode (10/1G BASE-PRX) and 10Gbit/s uplink/downlink symmetric mode (10G BASE-PR).
In order to achieve the compatibility of 10G EPON and 1G EPON and the smooth evolution of the network, the IEEE 802.3av standard has special considerations in wavelength allocation and multipoint control mechanisms to ensure the coexistence of 10G EPON and 1G EPON systems under the same ODN. 10G EPON has followed the 1G EPON MAC and MPCP protocols as much as possible, made a few modifications to the MPCP protocol, and defined a new PHY layer.
(2) Main changes in the PHY layer
Optical power budget
The 10G EPON standard specifies a higher link optical power budget (Power Budget). In addition to defining the same 20dB and 24dB as EPON, it also defines an optical channel insertion loss of 29dB according to actual networking requirements. The 10G EPON standard defines three types of power budgets for asymmetric and symmetric transmission rates:
——Asymmetric (10G/1G): PRX10, PRX20, PRX30.
——Symmetry (10G/10G): PR10, PR20, PR30.
Wavelength division
In terms of wavelength planning, in order to achieve compatibility with 1G EPON, 10G EPON does not use the 1490nm downstream wavelength used by the 1G EPON system and considers avoiding analog video wavelengths (1550nm) and OTDR test wavelengths (1600~1650nm), IEEE 802.3 The av standard selects 1577nm as the wavelength of the 10Gbit/s downstream signal (wavelength range 1574~1580nm). Therefore, in the downstream direction, 10Gbit/s signals and 1Gbit/s signals are WDM methods. In the upstream direction, the wavelength of the 1Gbit/s signal is 1310nm (1260~1360nm), and the IEEE 802.3av standard stipulates that the upstream wavelength of the 10Gbit/s signal is 1270nm (1260~1280nm). The two overlap, so WDM cannot be used. The dual-rate TDMA method can be used. The 10G EPON OLT can simultaneously discover 10G/10G ONUs, and the three types of ONUs, 10G/1G ONU and 1G/1G ONU, can coexist.
New PCS layer
10G EPON uses 64B/66B encoding, and the efficiency is 97%, which is significantly improved compared with 1G EPON's 8B/10B (efficiency 80%). The FEC function of 10G EPON uses RS (255, 223) coding, which can increase the optical power budget by 5 to 6 dB. Compared with the RS (255, 239) coding of 1G EPON, the FEC capability is stronger.
(3) Major changes in MPCP layer
The 10G EPON system needs to support asymmetric and symmetrical transmission rates and be compatible with the existing EPON technology. It needs to extend the MPCP protocol (IEEE 802.3) of EPON and add a 10Gbit/s capability notification and negotiation mechanism. This can make full use of the existing EPON implementation scheme, greatly reducing the cost of chips and equipment.
Add Discovery Information bytes in the discovery GATE frame to inform the ONU OLT's capabilities, and extend the downstream GATE message to support the OLT to open different discovery windows for ONUs with different upstream rates.
Add Discovery Information bytes to the Register Request frame to inform the OLT ONU capabilities.
(4) Churning function
In the EPON system, the triple churning method is used to encrypt the OLT downstream data to improve the security of the downstream data. However, the application of the existing triple agitation scheme in the 10G EPON system has the problems of complex circuit implementation and low encryption security. To solve the above problems, IEEE 802.3av defines a Churning scheme suitable for 10G EPON systems, which improves the security of 10G EPON downstream data.
The stirring of the 10G EPON system uses 3 cascaded stirrers, each of which performs a prescribed single stirring operation, and the stirring key used for each stirring is completely different. The 24-bit key used by the first-level agitator is (X1～X8, P1～P16)1; the 24-bit key used by the second-level agitator is (X1～X8, P1～P16)2; The 24bit key used by the agitator is (X1～X8, P1～P16)3. The churn key is the exclusive OR (XOR) result of the three 3-byte data extracted by the ONU from the upstream user data and the three 3-byte random numbers respectively.
See Figure 1 for details.
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