Spectral and Temporal Analysis of the NGPON2 Short-Term Wavelength Drift for 10Gbit/s Bursts

Focus on Time-Dependent Wavelength Drift of DMLs Under Burst-Mode Operation for NG-PON2

“…The heterodyne detection method allows a wide observation range (O and C bands) with a high accuracy. Time resolution can be lower than the bit duration at 10Gb/s [10], [11]). However, its main drawback is the relatively complex offline processing.…”

“…We propose here a synthesis of our previous works on the time-dependent wavelength drift of DMLs under burst-mode operation for TWDM [10], [11] with a complementary description of drift measurements methods and new results. The ITU-T recommendations are recalled in Section II and compared to the spectral measurements done on a precommercial TWDM NG-PON2 system.…”

Hitless wavelength assignment in filterless optical access networks

“…When a laser is turned on, it is subject to strong frequency drifts before it reaches a steady-state emission at a fixed wavelength. Such frequency drifts might be extremely large, up to tens of GHz has been recently measured [8]. This is clearly an issue, especially when UDWM operations on 6.25 or 3.125 GHz grids are targeted [5,6]: in this case a "turning-on" laser might be wandering over tens of running channels, clearly creating service interruptions.…”

“…As an example, an 8×1.25 Gb/s on a 6.25 GHz grid fits nicely an AWG with a 100 GHz period and 50 GHz channel bandwidth: in this case, the wake-up zones are naturally interleaved to the transmission bands (with 100 GHz spacing and 50 GHz bandwidth). We note that the wake-up zones must be wide enough to fully contain any laser's wavelength drift associated to the activation: in the proposed example, a bandwidth of 50 GHz is more than enough to fully contain all laser's drift [8]. Once that the laser has been activated in a Wake-up Zone, the negotiation can begin and the ONU sends a request to the OLT asking for a free wavelength slot: we note that a conflict might occur at this stage, in the event that more than one ONU activate simultaneously within the same Wake-up zone during the negotiation stage; however, this cannot introduce any service disruption on already active channels, while it might cause a delay on the overall activation time.…”