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OR GPON headend sites

Is there anyway to see which exchanges Openreach are using for GPON OLT headends?

Just curious as to how many exchanges they will be left with once the move to FTTP is complete and the non GPON sites shutdown and sold off. Ive also seen conflicting info as to how long a GPON line can be some sources say 20km some 40km
 

Dassa

Casual Member
I'm not sure on the first question. I don't think that Openreach has published a list of the ~4600 exchanges they plan to close, only a list of the first 100 or planned by 2030.

For what its worth, I think that the timing of (and to some extent selection of exchanges in) the exchange closure programme will end up being very opportunistic and depend heavily on several factors:
1. FTTP / FTTC penetration in the exchange area.
2. PSTN withdrawal in the exchange area.
3. The number of non-consumer services provided from an exchange (e.g. Ethernet).
4. The extent to which the exchange is used to support diversely provided services in other exchange areas. (This will probably be one of the biggest challenges in rationalising exchanges in urban areas with commercial premises, you will always need two "nearby" exchanges, even when one will do from a capacity perspective).
5. The value of the land the exchange sits on.

I can see some exchanges closing quicker than 2030 if FTTP installation and PSTN withdrawal goes well.

With respect to PON range, for GPON there are three figures:
a. Maximum theoretical range (based on timings, etc.) is specified as 60km.
b. Maximum achievable range with latest optics is around 58km (I think with a 4:1 split).
c. Maximum (fibre) distance between closest and furthest node on the PON is 20km.

Having said the above, I assume that Openreach will be designing to accommodate future technologies and the only figure above which I know to be the same for XGSPON is (c), I can't find figures for (a) and (b).
 

Dassa

Casual Member
No, in the general GPON case, a customer could be 58km from the headend, but if they are then the nearest customer on the same PON can't be closer than 38km.

If you don't have a split in the PON (i.e. its not really a PON) then 60km is probably the answer (there are lots of other fibre standards which will do point to point over much longer distances, but these won't be used for domestic customers).

In the BT Openreach case, the answer is "I don't know". If BT are designing according to GPON capability then 58km is the correct answer (although as I note above, that is with a small split). If they are designing more conservatively (because they think future technologies might have more restrictive requirements) then a shorter distance might be correct.

As I note above, I can't find a maximum range in the XGSPON specification whilst it is clearly detailed for GPON. The only number I can find for XGSPON is the distance between the closest and furthest remote node (20km, same as GPON).

It is fair to say that the maximum distance will be between 20km and 60km (but I know that doesn't answer your question).
 

Dassa

Casual Member
Just to follow up, if you Google for XGSPON range then you get a lot of results which say the maximum range is 100km. I can't find anywhere reliable (e.g. a standard) that says that though. If you were to believe that random internet wisdom then you might assume that BT would design to the full 58km GPON range.
 
No, in the general GPON case, a customer could be 58km from the headend, but if they are then the nearest customer on the same PON can't be closer than 38km.

If you don't have a split in the PON (i.e. its not really a PON) then 60km is probably the answer (there are lots of other fibre standards which will do point to point over much longer distances, but these won't be used for domestic customers).

In the BT Openreach case, the answer is "I don't know". If BT are designing according to GPON capability then 58km is the correct answer (although as I note above, that is with a small split). If they are designing more conservatively (because they think future technologies might have more restrictive requirements) then a shorter distance might be correct.

As I note above, I can't find a maximum range in the XGSPON specification whilst it is clearly detailed for GPON. The only number I can find for XGSPON is the distance between the closest and furthest remote node (20km, same as GPON).

It is fair to say that the maximum distance will be between 20km and 60km (but I know that doesn't answer your question).
Fantastic makes sense now thanks
 

RobWiFiScotland

Casual Member
@bluedalmatian You won't find a publicly available list of these exchanges. The lists do exist, but they are only available to Openreach Communication Providers.

As Dassa has said, whether the exchange is a GPON primary will not be the only factor in whether it is scheduled to be closed, and as they are intending to bring the exchange estate down ultimately from 4600 to roughly 1000 there is a good chance that existing primary exchanges may still close.
 
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