User:Gkr wiki/10G-EPON

The term 10G-EPON refers to 10Gb/s Ethernet Passive Optical Network architecture standardized by the IEEE P802.3av task force (http://www.ieee802.org/3/av/). The task force is working on two configurations: symmetric, operating at 10 Gb/s data rate in both upstream and downstream directions, and asymmetric, operating at 10 Gb/s in the downstream direction and 1 Gb/s in the upstream direction.

Standartization Timeline
In March 2006, IEEE 802.3 working group held call for interest (CFI) for 10Gb/s EPON study group. According to the CFI materials, representatives from the following companies supported the formation of the study group : Advance/Newhouse Communications, Aeluros, Agilent, Allied Telesyn, Alloptic, Ample Communications, Astar-ODSM, Broadcom, Centillium Communications, China Netcom, China Telecom, Chunghwa Telecom, Cisco Systems, ClariPhy Communications, Conexant Systems, Corecess, Corning, Delta Electronics, ETRI, Fiberxon, FOTEK Optoelectronics, ImmenStar, Infinera, ITRI, KDDI R&D Labs., K-Opticom, Korea Telecom, NEC, OpNext, Picolight, Quake Technologies, Salira Systems, Samsung Electronics, Softbank BB, Teknovus, Teranetics, Texas Instruments, Telecom Malaysia, TranSwitch, UNH IOL, UTStarcom, Vitesse.

By September 2006, the study group has completed its charter and IEEE 802.3 formed the 802.3av task force to produce the draft standard for 10 Gb/s EPON.

The following are the major milestones in 10Gb/s EPON study group:

Symmetric 10 Gb/s EPON (10/10G-EPON)
Symmetric-rate 10/10G-EPON supports transmit and receive data paths operating at 10 Gb/s. The main driver for 10/10G-EPON is the necessity to provide adequate downstream and upstream bandwidth to support MDU environment. When deployed in MDU configuration, one EPON may be connected to up to a thousand subscribers.

The 10/10G-EPON employs a number of functions that are common to other point-to-point Ethernet standards. For example, such functions as 64B/66B line coding, self-synchronizing scrambler, or gearbox are also used in 10GBASE-SR, 10GBASE-LR, 10GBASE-ER, 10GBASE-LRM, and 10GBASE-KR types of Ethernet links.

Asymmetric 10 Gb/s EPON (10/1G-EPON)
The asymmetric 10/1G-EPON appear less challenging then the symmetric option, as this specification relies on fairly mature technologies. The upstream transmission is identical to that of the existing 1G-EPON (as specified in IEEE Std. 802.3ah), and will rely on field-proven and mass deployed burst-mode optical transceivers. The downstream transmission, which uses continuous-mode optics, will rely on the maturity of 10 Gb/s point-to-point Ethernet devices.

Power budgets
The 802.3av defines several power budgets, denoted either PR or PRX. PRX power budget describes asymmetric–rate PHY for PON operating at 10 Gb/s downstream and 1 Gb/s upstream. PR power budget describes symmetric–rate PHY for PON operating at 10 Gb/s downstream and 10 Gb/s upstream. Each power budget is further identified with a numeric representation of its class, where value of 10 represents low power budget, value of 20 represents medium power budget, and value of 30 represents high power budget. The 802.3av draft standard defines the following power budgets:

Forward Error Correction
The 10G-EPON employs stream-based forward error correction (FEC) mechanism based on Reed Solomon(255, 223). The FEC is mandatory for all channels operating at 10 Gb/s rate, i.e., both downstream and upstream channels in symmetric 10Gb/s EPON and the downstream channel in the 10/1 Gb/s asymmetric EPON. (Upstream channel in the assymetric EPON is the same as in 1 Gb/s EPON, i.e., optional frame-based FEC using RS(255, 239).)

Backward Compatibility
The 10G-EPON task force focuses on defining a new physical layer, keeping the MAC, MAC Control and all the layers above unchanged to the greatest extent possible. This means that users of 10G-EPON can expect backward compatibility of network management system (NMS), PON-layer operations, administrations, and maintenance (OAM) system, DBA and scheduling, and so on.

Coexistence with 1G-EPON
The 802.3av task force places significant emphasis on enabling simultaneous operation of 1 Gb/s and 10 Gb/s EPON systems on the same outside plant. In the downstream direction, the 1 Gb/s and 10 Gb/s channels are separated in the wavelength domain, with 1 Gb/s transmission limited to 1480-1500 nm band and 10Gb/s transmission using 1575-1580 nm band.

In the upstream direction, the 1 Gb/s and 10 Gb/s bands overlap. 1 Gb/s band spreads from 1260 to 1360 nm; 10 Gb/s band uses 1260 to 1280 nm band. This allows both upstream channels to share spectrum region characterized by low chromatic disperson, but requires the 1 Gb/s and 10 Gb/s channels to be separated in time domain. Since burst transmissions from different ONUs now may have different line rates, this method is termed dual-rate TDMA.

Various OLT implementations may support 1 Gb/s and 10 Gb/s transmissions only downstream direction, only upstream direction, or in both downstream and upstream directions. The following table illustrates which ONU types are simultaneously supported by various OLT implementations: