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Hi Glen: The cost of tunable optics quite depends on the tuning scheme, tuning range .
The cost of tuning parts are generally independent with the bit rate, especially for the tunable receiver, it’s always tunable filter + wide band
receiver, so usually, the higher cost of the fixed transceiver is , the less ratio will be the cost of tuning parts accounts. _____________________________________________________________________________________________________________________________ According to my latest market data, the cost of tunable ONU optics today is ~9x that of 10G/10G-EPON ONU optics. Projections out to 2020 show it
to drop to 3.5x the cost of 10/10 ONU optics, which is still very high. Is this not why after completing NG-PON2 standard, SG15 shifted focus to XGS-PON that uses a fixed single wavelength 10/10 optics? If the same cost ratio between tunable and fixed optics remains for the 25G tunable and 25G fixed, From: Glen Kramer [mailto:glen.kramer@xxxxxxxxxxxx]
Somehow, just because the end target is 100G-EPON, people think that we need to utilize the 100G EPON capacity from day one. And if we don’t have
100G ONUs at day one, then we have to fill this capacity with 25G ONUs. This is not what we set to do. The generation 1 is a
single-lane EPON. Yes, starting with tunable optics and utilizing 4 lanes will provide 4x of sustained throughput per ONU. But that would be at more than 4x the cost. According to my latest market data, the cost of tunable ONU optics today is ~9x that of 10G/10G-EPON ONU optics. Projections out to 2020 show it
to drop to 3.5x the cost of 10/10 ONU optics, which is still very high. Is this not why after completing NG-PON2 standard, SG15 shifted focus to XGS-PON that uses a fixed single wavelength 10/10 optics? If the same cost ratio between tunable and fixed optics remains for the 25G tunable and 25G fixed, then the cost of 50G ONUs will likely be lower
than tunable 25G ONUs. A 50G ONU obviously can burst at 50Gb/s peak rate, but additionally can operate as a 25G ONU on either of the channels, or even can operate as two independent 25G ONUs. So, we may spend time and efforts developing the first generation
based on tunable optics, but then why wouldn’t operators just skip gen 1 and go directly to 50G ONUs with 2 fixed channels? Glen From: Francois Menard [mailto:fmenard@xxxxxxxxxxx]
Marek, Here is what I understand so far: Per what Glen has presented: The OLT starts with a Gen 1 transceiver, which is stuck at 25 Gbps until it is replaced with a Gen 2 at 50 Gbps.
Only the OLT transceiver is replaced with a Gen 3 transceiver, would it then become possible to add 100 Gbps ONUs on the PON. With a Gen 1 OLT transceiver on the PON, 100 Gbps ONUs would be limited to 25 Gbps. However, in NG-PON2, the use of an external WM allows for different OLT ports (or different OLT’s) to be the source of the additional instances of
10 Gbps channel (up to 8 from 8 different line cards or OLT shelves is allowed). Therefore this allows pay as you grow, in service, with no downtime without requirement of retiring out OLT transceivers. Is this a benefit or a pain in the rear end for operators
? Benefits allow for greater reliability, pay as you grow from cheaper 10 Gbps fixed XFPs/SFP+ with burst mode receivers. Pain in the butt means dealing with the WM and increased footprint. With regards to the benefits of being able to get a 25 Gbps Tunable Tx / Tunable Rx ONU to roam across channels, here are the benefits:
-=Francois=- -- Francois Menard AEPONYX inc. Cell: +1 (819) 609-1394 |