The next generation of passive optical networks is moving ahead with ITU-T approval of the ITU-T G.989 series of standards for 40 Gbps PON and first-stage approval (“consent”) of ITU-T G.989.2 Amendment 1. The standards, also known as NG-PON2, represent a major milestone, as the previous maximum PON speed was 10 Gbps.
Amendment 1 provides a further update to the NG-PON2 physical layer specification, ITU-T explains in a press release.
40 Gbps PON
NG-PON2 relies substantially on multi wavelength time and wavelength division multiplexed (TWDM) PON and a point-to-point systems architecture to boost fiber network access beyond 10 Gbps.
Typically, a TWDM-PON network consists of four to eight wavelengths in both directions, with each able to transport data at a maximum rate of up to 10 Gbps, for a total of 80 Gbps bi-directionally. The upstream/downstream wavelength can also operate at a lower 2.5 Gbps rate.
The typical distance between NG-PON2 optical network terminals (ONT) and optical networking units (ONU) is around 40 kms with one OLT able to support as many as 256 ONUs.
Significantly, carriers can reuse existing fiber optic distribution networks when upgrading to NG-PON2, according to ITU-T.
NG-PON2 advances the capabilities of previous 1 Gbps ITU-T G.984 and 10 Gbps XG-PON1 (ITU-T G.987) series of standards. It consists of three standards:
- ITU-T G.989.1 describes the general requirements of NG-PON2 systems.
- ITU-T G.989.2 specifies characteristics of the NG-PON2 physical media dependent (PMD) layer.
- ITU-T G.989.3 specifies the NG-PON2 frame formats, messages, and protocols for data transmission.