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Initial PON (1990s) were based on ATM framing (APON, BPON), ATM-based BPON were inefficient, majority of traffic through the access network was IP traffic, Ethernet based PON (EPON), QOS-aware Gigabit Ethernet (GbE) (VLANs, prioritization, OAM) and integration with other Ethernet equipment, Gigabit-capable Passive Optical Network (GPON) proposed by FSAN members (Quantum Bridge et. al) – dual Gigabit speed ATM/Ethernet PON to IEEE 802.3ah – had to continue this work within the ITU. EPON and GPON both draw on G.983, the BPON standard, (PON operation, ODN framework, wavelength plan, and application), designed to better accommodate variable length IP frames at Gigabit line rates.

GPON GEPON Comprehensive Comparison Table

ComparisonGPONGEPON
GPON GEPON Basics
  • ITU Standard G.984
  • ITU Standard G.987 for 10Gbits
  • Downstream 10Gbits/s, Upstream 2.488/10Gbits/s
  • Uses GPON Encapsulation Method (GEM), fragmented packets or ATM (most implementations use GEM as ATM is expensive)
  • Sometimes called GEPON (Gigabit Ethernet Passive Optical Network)
  • IEEE 802.3 standard, ratified as 802.3ah-2004 for 1Gbits/s
  • IEEE 802.3av standard for 10Gbits/s
  • Uses standard 802.3 Ethernet data frames
GPON GEPON Link Speed
  • GPON 2.448 Gbpsin the downstream direction and 1.24416 Gbpsin the upstream direction,
  • GPON in GEM mode can achieve ~ 95% efficiency of its usable bandwidth
  • GPON G.987 and EPON 802.3av are the same link speed EPON can scale via 802.3 standards 1Gbits/s, 10Gbits/s, etc.
  • GPON OLTs connect to the provider network using ATM switches or convert to Ethernet
  • whereas EPON is symmetrical 1.25 Gbps(1.0 Gbpsprior to 8B/10B coding)
  • EPON efficiency reaches 97.13% to 98.92% of the efficiency of a point-to-point 1GbE link. While
  • EPON can be operated in what is typically termed ‘turbo mode’ – downstream EPON data rate is doubled to 2.5Gbps, thus enabling bandwidth throughput comparable to GPON. EPON OLTs connect to the provider network using cost-efficient devices, such as Ethernet switches and routers.
  • Ethernet switches and routers use 802.3 as their standard as does EPON
GPON GEPON Splitting Ratios
  • GPON defines an upper limit
  • Promises to support 128 (with FEC)
  • Typical split ratio is 64
  • Standard supports a minimum of 32 but no upper limit
  • Split ratio defined by the services and bandwidth the provider wants to support
  • Typical split ratio is 32 and 64 with FEC
  • EPON can deploy cheaper optics at the ONU as it does not need to reach a split ratio of 128
GPON GEPON Similarities
  • Both have an Optical Line Terminal (OLT) at the headend
  • Both use passive optical splitters in the Optical Distribution Network (ODN)
  • Both have multiple Optical Network Units (ONUs) or Optical Network Terminals (ONTs) at the subscriber
  • Both utilize WDM: 802.3ah/ITU G.984 Downstream 1490nm, Upstream 1310nm, 802.3av/ITU G.987 Downstream 1260-1280nm, Upstream 1575-1580nm
  • Standards define different loss budgets but typically use 28dB which corresponds to 32 split at 20km
  • Forward Error Correction (FEC) is used to gain more loss budget
  • Both provide support for Voice, Video and Data
GPON GEPON Differences
  • GPON Provides native support for different services. As this is an ITU standard it is aimed at Telcos
  • Provides ATM for Voice
  • Ethernet for Data
  • Proprietary Encapsulation for other voice services
  • GPON equipment requires multiple protocol conversions, segmentation and reassembly (SAR), virtual channel (VC) termination and Both utilize a common optical infrastructure, but very different in execution. EPON extended point-to-point protocol (PPP)
  • EPON assumes that data today starts and ends as Ethernet and therefore 802.3 frame format is appropriate. Used widely in the Enterprise and Asian ISP markets.
  • IP data services
  • VoIP
  • IPTV – Supports multicast so uses less bandwidth
GPON GEPON LayeringGPON on the other hand is fundamentally a transport protocol, wherein Ethernet services are adapted at the OLT and ONTEPON is based upon IEEE 802.3 modified to support Point-toMultipoint (P2MP) connectivity. Ethernet traffic is transported natively and all Ethernet Features are fully supported.
GPON GEPON Framing

GPON-GEPON-comparison---GPON-Frame

GPON-&-GEPON-comparison—GPON-Frame

GPON-GEPON-comparison---GePON-Frame

GPON-&-GEPON-comparison—GePON-Frame

GPON GEPON Costs
  • xDSLstill widely deployed but moving to PON
  • ATM devices supporting DSL and GPON expensive and being replaced with Ethernet devices
  • North American Telcos have historically used GPON
  • No native support for Multicast so uses proprietary solution or more bandwidth
  • Timing constraints tighter with GPON so optics more expensive GPON adds a layer of complexity to data networks (including VoIP), as traffic must be converted to IP
  • Approximately 60% of PON subscribers worldwide Scale reducing cost and driving investment
  • North American Cable Operators also moving to EPON
  • Ethernet devices approximately 1/10 the cost of ATM devices Optics less expensive than GPON
GPON GEPON Summary
  • Both EPON and GPON recognized the need to evolve PON to being a Gigabit capable solution for transporting Ethernet IP traffic.
  • native Ethernet to support the PON P2MP architecture, while GPON wished to extend the life of GFP framed SONET/SDH GPON link rates match ITU standards like OC3, OC12, etc
  • North American Telcos SONET/GPON Equipment based on ITU/SONET typically more expensive/complicated
  • Both utilize a common optical infrastructure, but very different in execution. EPON extended
  • EPON link rates match IEEE standards like 1Gbs, 10Gbs, etc
  • North American Cable Operators adopting EPON
  • EPON is widely deployed world-wide
  • Ethernet and IP scale reducing costs and driving investment in EPON systems
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