The 10Gbit/s Ethernet Passive Optical Network standard, better known as 10G-EPON allows computer network connections over telecommunication provider infrastructure. The standard supports two configurations: symmetric, operating at 10Gbit/s data rate in both directions, and asymmetric, operating at 10Gbit/s in the downstream (provider to customer) direction and 1Gbit/s in the upstream direction. It was ratified as IEEE 802.3av standard in 2009. EPON is a type of passive optical network, with Time-division multiple access which is a point-to-multipoint network using passive fiber-optic splitters rather than powered devices for fan-out from hub to customers.
By September 2006, IEEE 802.3 formed the 802.3av 10G-EPON Task Force[3] to produce a draft standard. In September 2009, the IEEE 802 Plenary ratified an amendment to 802.3 to publish 802.3av amendment as the standard IEEE Std 802.3av-2009.[4]
Draft D2.0 produced. Working Group balloting began.
November 2008
Cut-off date for last technical change
January 2009
Draft D3.0 produced. Sponsor balloting began.
September 2009
Standard approved.
The work on the 10G-EPON was continued by the IEEE P802.3bk Extended EPON Task Force,[5] formed in March 2012. The major goals for this Task Force included adding support for PX30, PX40, PRX40, and PR40 power budget classes to both 1G-EPON and 10G-EPON. The 802.3bk amendment was approved by the IEEE-SA SB in August 2013 and published soon thereafter as the standard IEEE Std 802.3bk-2013.[6] On 4 June 2020, the IEEE approved IEEE 802.3ca, which allows for symmetric or asymmetric operation with downstream speeds of 25Gbit/s or 50Gbit/s, and upstream speeds of 10Gbit/s, 25Gbit/s, or 50Gbit/s over the same power-distance-splitter budgets.[7][8]
Architecture
Symmetric (10/10G-EPON)
Symmetric-rate 10/10G-EPON supports both transmit and receive data paths operating at 10Gbit/s. The main driver for 10/10G-EPON was to provide adequate downstream and upstream bandwidth to support multi-family residential building (known in the standard as Multi Dwelling Unit or MDU) customers. When deployed in the MDU configuration, one EPON Optical Network Unit (ONU) 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 optical fiber types of 10 Gigabit Ethernet links.
Asymmetric (10/1G-EPON)
The asymmetric 10/1G-EPON appear less challenging than the symmetric option, as this specification relies on fairly mature technologies. The upstream transmission is identical to that of the 1G-EPON (as specified in IEEE standard 802.3ah), using deployed burst-mode optical transceivers. The downstream transmission, which uses continuous-mode optics, will rely on the maturity of 10Gbit/s point-to-point Ethernet devices.
Efficiency
Like all EPON networks, 10G-EPON transmits data in variable-length packets up to 1518 bytes, as specified in the IEEE 802.3 standard. These variable-length packets are better suited to IP traffic than the GEM frames used by other Passive Optical Networks, such as GPON which is designed for multiple traffic types including ATM, Ethernet, T1 and POTS. This can significantly reduce 10G-EPON's overhead in comparison to other systems. Typical 10G-EPON overhead is approximately 7.42%. Typical GPON overhead is 13.22%. This high data-to-overhead ratio also enables high utilization with low-cost optical components.[9]
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 10Gbit/s downstream and 1Gbit/s upstream. PR power budget describes symmetric–rate PHY for PON operating at 10Gbit/s downstream and 10Gbit/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:
Power budget
Downstream line rate (Gbit/s)
Upstream line rate (Gbit/s)
Channel insertion loss (dB)
Notes
PRX10
10.3125
1.25
20
compatible with PX10 power budget defined for 1G-EPON by 802.3ah
PRX20
10.3125
1.25
24
compatible with PX20 power budget defined for 1G-EPON by 802.3ah
PRX30
10.3125
1.25
29
compatible with PX30 power budget defined for 1G-EPON by 802.3bk
PR10
10.3125
10.3125
20
compatible with PX10 power budget defined for 1G-EPON by 802.3ah
PR20
10.3125
10.3125
24
compatible with PX20 power budget defined for 1G-EPON by 802.3ah
PR30
10.3125
10.3125
29
compatible with PX30 power budget defined for 1G-EPON by 802.3bk
The 802.3bk added support for a new 10/10G-EPON and 10/1G-EPON power class for PR or PRX PMDs, respectively, as shown below:
Power budget
Downstream line rate (Gbit/s)
Upstream line rate (Gbit/s)
Channel insertion loss (dB)
Notes
PRX40
10.3125
1.25
33
compatible with PX40 power budget defined for 1G-EPON by 802.3bk
PR40
10.3125
10.3125
33
compatible with PX40 power budget defined for 1G-EPON by 802.3bk
Forward error correction
The 10G-EPON employs a stream-basedforward error correction (FEC) mechanism based on Reed-Solomon(255, 223). The FEC is mandatory for all channels operating at 10Gbit/s rate, i.e., both downstream and upstream channels in symmetric 10Gbit/s EPON and the downstream channel in the 10/1Gbit/s asymmetric EPON. Upstream channel in the asymmetric EPON is the same as in 1Gbit/s EPON, an optional frame-based FEC using Reed-Solomon(255, 239).
Usable bandwidth
10G-EPON uses 64B/66B line coding, thus encoding overhead is just 3.125% compared to 25% encoding overhead that 1G-EPON has due to its use of 8b/10b encoding.
The usable bandwidth in 10G-EPON is 10Gbit/s out of a raw bandwidth of 10.3125Gbit/s.
Backward compatibility
The 10G-EPON standard defines 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 standard places significant emphasis on enabling simultaneous operation of 1Gbit/s and 10Gbit/s EPON systems on the same outside plant. In the downstream direction, the 1Gbit/s and 10Gbit/s channels are separated in the wavelength domain, with 1Gbit/s transmission limited to 1480–1500nm band and 10Gbit/s transmission using 1575–1580nm band.
In the upstream direction, the 1Gbit/s and 10Gbit/s bands overlap. 1Gbit/s band spreads from 1260 to 1360nm; 10Gbit/s band uses 1260 to 1280nm band. This allows both upstream channels to share spectrum region characterized by low chromatic dispersion, but requires the 1Gbit/s and 10Gbit/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 1Gbit/s and 10Gbit/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:
OLT Implementation
Supported ONU types
Downstream: two wavelengths Upstream: single rate
(1) 1G-EPON ONU (2) 10/1G-EPON ONU
Downstream: single wavelength Upstream: dual rate
(1) 10/10G-EPON ONU (2) 10/1G-EPON ONU
Downstream: two wavelengths Upstream: dual rate
(1) 1G-EPON ONU (2) 10/1G-EPON ONU (3) 10/10G-EPON ONU
