GPON 30000 foot level from someone who has been apart of large
enterprise GPON installation for ~ 15 years.
GPON is transport, not ethernet, think SONET or DWDM or any other
myriad transport layers.
GPON OLT ( Optical Line Terminal ) looks like a switch but it isn't,
in the Telco world it is called "shelf"
OLT is connected upstream to ethernet backbone; ex: direct ethernet or
via DWDM. Today this upstream is probably 100G, in the past it was
10G or 1G.
OLT has PON ports, our legacy install has 4 PON ports per blade and 8
blades per shelf.
PON has single fiber ( with different Tx and Rx lambda ) which
connects to a splitter ( anywhere from 16:1 to 64:1 )
The output of the splitter goes to an ONT ( Optical Network Terminal
), depending on the ONT it can have 1 to n ethernet ports,
100Mb/1Gb/10Gb.
The downstream (Tx) is sent to everyone, hopefully it is encrypted,
however that is an OLT configuration. Encryption did not used to be
enabled by default, we learned that in our initial installation when
the evil twin in our enterprise said they could see everything
transmitted to the ONT.
The upstream (Rx) is read via a timeslot ( think TDM ) allocated to each ONT.
So if you have managed to keep reading up to this point you will see
there is over subscription all through this system. From the upstream
connection, you have some number of PON ports/blade, then some number
of blades/OLT, add in the passive splitters and then the number of
ethernet ports on the ONT.
So, just because your system ( router/computer ) connects at some
speed you will never sustain anywhere near what your local connection
speed.
I hope I haven't bored to many people.
diana
KI5PGJ
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