TECHNICAL
Figure 1
the same fibre with more connected customers, or even by sharing networks with multiple operators. The new NG- PON2 standard, using transmission wavelengths in the 1535nm region for upstream transmission and in the 1600nm region for downstream transmission, employs more of the same fibre deployed and allows seamless overlays of new services to existing GPONs. New Challenges No matter where you are in the ODN, connector cleanliness and condition is critical. Fibre is often installed in harsh environments (e.g. dirty cellars) and damaged or dirty connectors can severely degrade service performance. Despite this, service providers or their contractors might opt not to test completely. One of the rationales is time—time per job, per inspection, and per number of connectors. Without testing, the risk is poor-quality installations and therefore poor service. Simply put, the impact of faulty installations will be customer churn.
Today’s GPON systems use 1490nm as a downstream channel and 1310nm as the upstream. XGS-PON uses 1578nm downstream and 1270nm upstream, which means you can overlay the XGS- PON service on the same plant as the GPON service. NG-PON2 uses the G.989 standard, which is a multi-wavelength access standard that supports TWDM technologies (see Figure 1). To physically implement the migration or activation of newer PON services requires network changes, especially in the central office. For leveraging existing ODNs, a coexistence element is needed. This can have different configurations depending on the technologies that the service provider wants to deliver. Essentially, it’s a passive optical coupler to combine GPON, XGS-PON, and NG-PON2 services up and downstream. The new NG-PON2 transmissions enable service providers to increase the FTTH networks’ bandwidth capacities and reduce deployment costs by sharing
Figure 2
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Volume 46 No.4 DECEMBER 2024
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