On Tue Feb 07, 2023 at 10:45:48AM +0000, Paul Brennan wrote:
> When considering both planning and operation, how much db is
> required to operate a steady and reliable service once you
> take the light budget and measured loss into consideration.
That's down to your system design.
> PON SFPs Optics rated for ? 31db (power budget) - What is the
> maximum tolerated loss and still have a working service
That is one element
So worse case you have 31dB to play with, thoguh check the
limits once installed in your kit, you'll see something like
(this is not a gpon)
Current Alarms Warnings
Measurement High Low High Low
Tx Power -7.42 dBm -1.00 dBm -10.00 dBm -1.99 dBm -9.03 dBm
Rx Power -7.54 dBm -1.99 dBm -23.01 dBm -3.00 dBm -22.21 dBm
You'll have alarms if you go too close to the limits. There is
hysteresis too so it'll want a bit more level to come up vs what
it takes to go down.
So while it'll work at 31 it won't be a happy place.
Against that you have losses - splitters, fibre, splices,
patches and have a varying quantity of, each with losses and
tolerances you have to work with. You may decide to use only good
parts and remake every splice that isn't perfect, track every little
bend loss. Or you may decide you need to be doing new installs
and allow your staff a little slack. So what's your longest
path, with worse case components (some statistics needed as
not all will be worse case at the same time, except when they are
and you have make it work anyway).
That's all fine you think, I'll allow a little wiggle room say
10%.
Then reality bites, you nailed this to some sticks in the wind,
some walls and burried some where animals(children,others) and
weather can get at it.
How often do you want to get called when it drops out and you've
no idea where that occured? Like with those wifi calls you have
no way to resolve. You like my wifi drops out calls?
Then you may wonder if 3dB margin was enough, maybe you want
6dB, or more.
The gap between your designed system loss and reality is for
you and your finanace people to argue over. Don't let them
win, you will be the one blamed.
brandon
