Interleaving

[#1]

Can it be switched off on fibre ?

[#2]

Not as far as we're aware I'm afraid.

[#3]

I believe interleaving is turned off by default on fibre but is enabled by the DLM (as with ADSL) if there are excessive errors on the line - I don't think ISPs have any direct control over it or the line profile though.
During a fault on my line a while back it was enabled (normal ping on the line to a local server was 10ms and with interleaving on another 20ms or so was added to that when it was on) - this was confirmed by the profile shown from the diagnostic tests.
From the 'bad' line:
Profile Name 20M-40M Downstream, Interleaving Low - 5M-10M Upstream, Interleaving On
and once the fault was resolved:
Profile Name 20M-40M Downstream, Interleaving Off - 5M-10M Upstream, Interleaving Off
Not sure if the DLM turned interleaving back off again or if it was as a result of something the openreach engineer did after fixing the fault.

[#4]

Mine has flipped from off to on to off to back on again whilst on the 80/20 trial.

[#5]

Quote from: flaminmoses

Can it be switched off on fibre ?

Not directly, I think, although my interpretation of this <a href="http://www.openreach.co.uk/orpg/home/products/super-fastfibreaccess/fibretothecabinet/fttc/downloads/GEA_FTTC_2%2063350%20111108.pdf>BT briefing document</a> is that ISPs can specify one of three DLM profiles for each customer's account, and the main effect of this change is to determine the interleaving settings applied.  There are three options: standard, where interleaving is applied automatically up to the level required to achieve stability on the line; speed, where interleaving is off; and stable, where interleaving is on.
The problem is that this is quite a new briefing from BT, so ISPs seem a bit unsure about the feature and how it works (there are posts about it over on the forums at www.thinkbroadband.com which indicate ISPs' uncertainty).  Adam & Alex at Plusnet are currently investigating this for me, because I've asked if I can go on the "Speed" profile to ensure interleaving is off.  I'll post back when I have an answer.

[#6]

Quote from: KevinG

Mine has flipped from off to on to off to back on again whilst on the 80/20 trial.

Have you unlocked the modem to find this out?

[#7]

While it's possible to unlock the modem* to find out a lot more information, I'm sure that none of us would deliberately breaks the rules, honest 
Just because it is relatively simple, generally safe and fully reversible doesn't mean we are allowed to do this to what appears to remain the property of Openreach 
Monitoring your ping times to a reliable stie (such as bbc.co.uk) from a command prompt will normally make it fairly obvious if somthing has been applied that increases latency.
Thinkbroadband Qualtiy Monitor is an excellent tool for monitoring latency.
* for technical reference only (HG612): http://huaweihg612hacking.files.wordpress.com/2011/11/hg612_unlock_instructions_v1-3.pdf

[#8]

Quote from: garywood84

Quote from: KevinG Mine has flipped from off to on to off to back on again whilst on the 80/20 trial. Have you unlocked the modem to find this out?

In short, yes.

[#9]

Quote from: walker23

* for technical reference only (HG612): http://huaweihg612hacking.files.wordpress.com/2011/11/hg612_unlock_instructions_v1-3.pdf

Also for technical reference only Huawei HG612 Graphing Scripts (for Windows users).