The Direct Fibre Debate (GPON vs PtP vs WDM-PON)

Another debate that has been going on is whether the NBN should use a PON or a PtP style deployment. In a recent consultation paper NBNCo outlined their position and rationale for choosing PON over PtP for the majority of customers.

It is NBN Co’s view that adoption of a PON architecture as opposed to a point-to-point architecture should be the primary network architecture for mass market services, because it can be substantially more economical for large radius coverage areas required in the Australian context, with savings in fibre and deployment, fibre management, power consumption and carbon footprint. In addition, an appropriately conceived PON architecture does not preclude the deployment of point to point Ethernet services as required for high end, substantial capacity, and mission critical services.1

The following is a quick overview of each technology.

GPON

  • Tried and tested deployment already in place
  • Generally regarded as cheaper to install
  • ITU-T G.984 standard
  • 2.5Gbps down, 1.25Gbps up
  • 10-20km reach2
  • 95% of connected homes in Australia use GPON
  • Used by Verizon for the largest current FTTH rollout in the US3
  • Potentially reduces the number of exchanges

PtP

  • Fibre runs from the exchange to the home
  • Requires more fibre
  • Uses standard Ethernet technology
  • Cost more to install. Could be anywhere between 1.1x to 4x4
  • Requires larger and more complex exchange
  • Can make aerial deployment difficult because of the number of fibre cables
  • Better for business where 1:1 is required

WDM-PON

  • Still in development
  • Not yet standardised
  • Uses different wavelength per subscriber
  • More expensive than GPON due to complexity of lasers5
  1. http://www.nbnco.com.au/wps/wcm/connect/1c18dc00439fe2a58b63ffc5166da634/NBN001_concept_paper_final.pdf?MOD=AJPERES [↩]
  2. http://docs.google.com/viewer?a=v&q=cache:R5EEeOGEupEJ:www.alliedtelesyneurope.com/media/pdf/active_vs_pon_a_wp.pdf+p2p+vs+pon&hl=en&gl=au&pid=bl&srcid=ADGEESjVOOp-6hHhDmk1-4C6qRleKzDWnbMdWPavAd_NkwEgggvuuINor9k4qPwUE0m-ZVmL_JF7vHG2IxV0htPFlN87g6MOoFIYpKE7UWGZonSEo9_Vst0py2t0AnMs2D6YZ1UmMWs1&sig=AHIEtbT6O5nwFPgaYb0DnZeuH4vxmtotHA [↩]
  3. http://en.wikipedia.org/wiki/Verizon_FiOS [↩]
  4. http://ozftth.blogspot.com/2009/05/nbn-pon-or-ptp-dispelling-myths.html [↩]
  5. http://ozftth.blogspot.com/2009/05/nbn-pon-or-ptp-dispelling-myths.html [↩]