GPON Optical Levels

Jameson, Daniel Daniel.Jameson at
Mon Oct 12 16:25:38 UTC 2015

A good general rule of thumb for optics is +-4.  Try to stay 4 db off the bottom,  and 4db off the top.   The sweet-spot RSL is  between 1/2 and 2/3 of the optical budget.  For PON,  typical OLT/ONT optics run Receive Max of -8,  and Min of -27 with an optical de-assert at -31.  The sweet-spot is between -17 and -20,  with a min/max of -12 to -23.

A typical PON system will have a TX power between +3 and +5,  with a 32 way split, add 15dB of insertion loss.  You should see -12 on the output of the first splitter (less the optical loss of the fiber between the OLT and the Splitter est .3/km)

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)

-----Original Message-----
From: NANOG [mailto:nanog-bounces at] On Behalf Of Colton Conor
Sent: Monday, October 12, 2015 10:58 AM
Subject: Re: GPON Optical Levels

Here is the link to the attachment as it looks like the list does not allow uploading attachment:

On Mon, Oct 12, 2015 at 10:47 AM, Colton Conor <colton.conor at>

> We are deploying our first GPON network, and are trying to get a sense 
> of what is a good optical level per ONT. The equipment install guide 
> says the
> following:
> Measure the levels of the 1550 dBm and 1490 dBm receive optical inputs 
> using
> an optical power meter. The input range should be between -27.0 dBm to 
> -8
> dBm.
> Attached are the measurements I can see and graph from the ONT side.
> Trying to get a sense of what range we would graph as good
> (green) measured within the clear, what we could consider yellow as 
> working but out of optimal range, and what we could consider poor (red) range.
> What about the Laser Bias Current, Optics Module Voltage, and Optics 
> Module temperature?

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