Yes, there is an end-to-end budget for attenuation. Usually not an issue.

In our case (our local FTTP network which has <32 homes) Openreach came and replaced the main 32 way optical splitter as it was apparently 2dB out of specification and causing issues with signal headroom on new downstream installations (making the splice joint quality too critical).

Poor chap sat there for a good chunk of time redoing each of the 32 down-stream fibres to the new splitter but was happy to chat about it (i'd wandered out as our internet was down, and the main chamber with splitter is just around the corner from our house, in the expectation of someone working there).

Edited by deleted (Sat 08-Dec-18 19:16:28)

Thanks to everyone for your replies they have been very helpful and are much appreciated.

Why was he redoing those 32 splices, if the whole splitter is high, then it�s the splices before the splitter that are the issue, not those after.

In reply to a post by Zarjaz:

Why was he redoing those 32 splices, if the whole splitter is high, then it�s the splices before the splitter that are the issue, not those after.

He was replacing the splitter itself. Didn't look like a job for the feint hearted!

In reply to a post by kitcat:

The loss in the fibre is affected by the SFP used ( the bit that goes on the ends) these are rated for different distances. eg short medium long, SX,MX,LX (say up to 100meters,80m-10k , 8k to 100k etc.) and the quality of fibre. Look online if you want more technical detail on what is available now as my knowledge is slightly out of date in a fast moving field

Using a higher spec one at a shorter distance will blow the distant end and they should match both ends

No the SFP used does not effect the attenuation. The longer reaching and invariable more expensive SFP's use more powerful lasers, which is why they are more expensive. IT should be noted that the longer reaching SFP's present a laser safety risk and you should never look into the SFP and/or cable. Especially as they all oporate in the infre-red region and you can't see jack anyway, Use the camera from a mobile phone to see if you have light.

Also modern SFP's will reduce the laser power do you don't burn out the photodiode at the receiving end. Older GBIC's didn't do that so you often had to but in attenuators for testing purposes or if the link was not long enough etc.

So the component itself was faulty ? Interesting, you�d hope these items were tested before being sent out from the manufacturer wouldn�t you ?

Use the camera from a mobile phone to see if you have light.

...... or better still, put your light meter on it ??

True, but that requires going and digging the light meter out from wherever it is currently hiding, finding the right patch lead and possibly coupler and hoping the battery has not run out. Alternatively I can just whip my mobile out and test to see if I have light, and reserve the light meter for when I have light but I am still not getting link.

You mean you are installing some part of our FTTP circuits and not doing a proper light test? Do you work for Openreach, or one of the shoddy sub-contractors who are the cause of a high proportion of faults?

Such as perhaps the 32-connection splitter cockup here?

Edited by RobertoS (Mon 10-Dec-18 10:02:50)

[what Bob said]