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Reported signal on ONU vs OLT

Is the signal reported in the OLT and in UNMS the signal received at the OLT from the ONU, or is it the signal received on the ONU and reported back to the OLT?

 

Thanks,

Joe

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Re: Reported signal on ONU vs OLT

It is sent from the ONU to the OLT (as part of G.984/DBRU).  It's the OLT that reports this data to UNMS.

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Re: Reported signal on ONU vs OLT

Okay, so the only signal that is ever reported anywhere (on the ONU, in the OLT, and in UNMS) is all the same signal, which is the signal received at the ONU, correct?
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Re: Reported signal on ONU vs OLT

Correct.  When talking about GPON it's common only to mention the 1310nm upstream signal strength.

It's the signal coming out of the OLT and it's the one you might measure with your OPM.

 

The 1490nm downstream signal is the one coming out of your ONU.  It's much harder to measure with your OPM as most ONU's don't spit out signal unless they also receive.  In normal daily operatrions nobody checks the downstream signal strength.

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Re: Reported signal on ONU vs OLT

That's what I needed to know! Thanks for explaining it!
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Re: Reported signal on ONU vs OLT

This seems opposite to me after running other PON's, and Docsis.  Downstream is from the Central system, Upstream is to the central system.  Aka Central system equals OLT, CMTS etc.

 

The spec sheet is messed up to.  GPON says 2.488 Gpbs Upstream (TX) and 1.244 Gbps Downstream (RX)...  Upstream and Downstream are backwards on this document.  1490 (upstream) Transmit which is actually down to the ONU and 1310  (downstream?) is actually upstream RX to the OLT.  

 

I will verify with a light meter, but I believe the correct is this.  

 

GPON is 2.488Gbps Downstream at 1490nm and 1.244 Gbps Upstream at 1310 at the OLT.  


Downstream = Receive on the ONU, Upstream is Transmit.  

 

 

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Re: Reported signal on ONU vs OLT


windwaterwaves wrote:

This seems opposite to me after running other PON's, and Docsis.  Downstream is from the Central system, Upstream is to the central system.  Aka Central system equals OLT, CMTS etc.

 

The spec sheet is messed up to.  GPON says 2.488 Gpbs Upstream (TX) and 1.244 Gbps Downstream (RX)...  Upstream and Downstream are backwards on this document.  1490 (upstream) Transmit which is actually down to the ONU and 1310  (downstream?) is actually upstream RX to the OLT.  

 

I will verify with a light meter, but I believe the correct is this.  

 

GPON is 2.488Gbps Downstream at 1490nm and 1.244 Gbps Upstream at 1310 at the OLT.  


Downstream = Receive on the ONU, Upstream is Transmit.  

 

 


You use your OPM (light meter) to measure signal coming from the OLT, to the ONU, at 1310nm.

Whether you want to call it downstream or upstream, the OLT spits out 1310nm.

Specs always (should) mention 1310nm as upstream (OLT->ONU), 1490nm as downstream (ONU->OLT)

If somewhere it's called the opposite, it's wrong.

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Re: Reported signal on ONU vs OLT

EPDR you are 100% incorrect on this topic.

 

ITU-T G.984.x specifies the following

OLT - Optical Line Termination

ONT - Optical Network Termination/Optical Network Unit

 

The OLT transmits DOWNSTREAM at 1490nm to the ONU at 2.5gbps

The ONU transmits UPSTREAM at 1310nm to the OLT at 1.25gbps

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