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?
Here is the link to the attachment as it looks like the list does not allow uploading attachment: https://drive.google.com/file/d/0B7sFULLCnLvFdllHQUl6dnJfZ00/view?usp=sharin... On Mon, Oct 12, 2015 at 10:47 AM, Colton Conor <colton.conor@gmail.com> wrote:
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?
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@nanog.org] On Behalf Of Colton Conor Sent: Monday, October 12, 2015 10:58 AM To: NANOG Subject: Re: GPON Optical Levels Here is the link to the attachment as it looks like the list does not allow uploading attachment: https://drive.google.com/file/d/0B7sFULLCnLvFdllHQUl6dnJfZ00/view?usp=sharin... On Mon, Oct 12, 2015 at 10:47 AM, Colton Conor <colton.conor@gmail.com> wrote:
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?
On 12 October 2015 at 18:25, Jameson, Daniel <Daniel.Jameson@tdstelecom.com> wrote:
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. Regards, Baldur
On Mon, Oct 12, 2015 at 10:46:59PM +0200, Baldur Norddahl wrote:
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
Wouldnt a 1:32 splitter + a 9dB attenuation be the same? From the price/performance the 1:128 splitter should be much more expensive. We have seen happening the same converting a former p2p footprint to GPON and somebody got a left over p2p device connected. But this was a single incident so far. Flo -- Florian Lohoff f@zz.de We need to self-defend - GnuPG/PGP enable your email today!
participants (4)
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Baldur Norddahl -
Colton Conor -
Florian Lohoff -
Jameson, Daniel