GPON Optical Levels

Baldur Norddahl baldur.norddahl at
Mon Oct 12 20:46:59 UTC 2015

On 12 October 2015 at 18:25, Jameson, Daniel <Daniel.Jameson at>

> There should never be a need to attenuate a PON port unless you're working
> directly on the OLT (You should work through a splitter even directly in
> the CO/HE)

Here is a small secret: If you attenuate the PON port so the signal level
at the OLT is as low as possible, your network will be more robust against
people connecting P2P fiber media converters to your network. This is
because these devices typically have TX power that is significantly less
than your ONUs. By attenuate the signal you can bring the rogue signal
below the detection threshold of the OLT.

In my experience one way to do this is to always use 1:128 splits. Even if
you are only going to connect less than 32 ONUs, you will find that 1:128
can be more robust. In fact I discovered this little trick after we started
using 1:128 splits (for flexibility, not because we actually connect that
many clients). Because the fiber plant is shared with other service
providers, we used to have OLT crashes due to people connecting a media
converter they got from another service provider. I found that we had zero
of these issues where we had 1:128 splits.

Btw we use class C+ optics. This might work out differently if you have
class B optics.



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