" We ended having to build a tool to do the calculations for the techs:"
That's a great idea. On Tue, Aug 19, 2025 at 5:54 PM Mark Radabaugh <[email protected]> wrote: > There are two limitations - max distance due to both timing and light that > are currently 60km but I think it’s theoretically limited at 100km. > There is also a max difference between the closest and farthest ONT on any > given port - and that is typically 20km or 40km, but some platforms will > let you set something in-between 20 and 40km. > > If you are using 20km optics the max split doesn’t matter. > > If you are using 40km optics and you can put at ONT at 1m and one at > 20.001km and it should work, but the ONT at 21km won’t - unless you set the > max differential to 40km. It costs you a bit of bandwidth to do. > > 60km are the same way - 20 or 40km max differential. > > The bigger issue with 40 and 60km optics is return loss. You can keep > picking better optics at the OLT - A, B, C, C+ and increasing the output > power, but the ONT’s are all the same output power, and they transmit back > on the higher loss wavelength. The C and C+ optics have better receive > sensitivity and additional error correction (FEC), but ultimately even > though the ONT can hear the signal fine, it can’t communicate back to the > head end. > > You will likely also find that when running at >30km the difference in ONT > and OLT receive signals confuses the techs. They get very used to seeing > receive light levels that about match - but forget that the 1577nm > (0.2dB/km) downstream wavelength has much lower loss per km than the 1270nm > (0.35dB/km) upstream wavelength. We ended having to build a tool to do > the calculations for the techs: > > Customer:xxxxxxx-ont > RX at the ONT: -14.9 dB > TX from the ONT: 6.5 dB > Expected Loss: 28.5 dB > Actual Loss: 26.2 dB > Difference: -2.3 dB > RX at the OLT: -26.5 dB > Expected Loss: 34.9 dB > Actual Loss: 33 dB > Difference: -1.9 dB > Distance from OLT: 42.68 km > > > > > > > > > > > > > > Without it they tended to freak out - what’s wrong with the fiber - the > ONT is at -14.9dB and the OLT is seeing -26.5dB? Do the math at 42.68km > and they are both about 2dB better than the expected at that distance. > This one is within 3dB of theoretical - and good to go. > > Mark > > On Aug 19, 2025, at 4:55 PM, Chuck <[email protected]> wrote: > > There was in the beginning due to the timing and cuing of ONT upstream. > It was to ensure 32 ONTs could all be transmitting max traffic at the same > time. That is what Calix told me many years ago. > Sent from my iPhone > > On Aug 19, 2025, at 11:50 AM, Josh Luthman <[email protected]> > wrote: > > > From what I've read, the issue was the timing between the farthest & > closest ONT. There was no 20km timing limitation from OLT to anything. > > On Tue, Aug 19, 2025 at 12:39 PM <[email protected]> wrote: > >> Original GPON specs had a timing limitation of 20 km. >> >> >> >> >> >> *From:* AF <[email protected]> *On Behalf Of *Josh Luthman >> *Sent:* Tuesday, August 19, 2025 6:31 AM >> *To:* AnimalFarm Microwave Users Group <[email protected]> >> *Subject:* Re: [AFMUG] how is underground FTTH done? >> >> >> >> Class C optics are rated for 60km or 42mi. That's a hell of a distance >> when you're only doing 1:32. We did 1:2 and 1:32 on the sixteenth PON port >> until we built more to justify another OLT. >> >> >> >> On Mon, Aug 18, 2025 at 6:13 PM Chuck McCown <[email protected]> wrote: >> >> When you work out a 32:1 GPON, the timing distance limitations are >> exhausted before you run out of light. Splits are a 3 dB loss. A good >> splice will be .02dB. So don’t worry about splices. >> >> >> >> *From:* AF [mailto:[email protected]] *On Behalf Of *Dev >> *Sent:* Monday, August 18, 2025 9:56 AM >> *To:* AnimalFarm Microwave Users Group <[email protected]> >> *Subject:* Re: [AFMUG] how is underground FTTH done? >> >> >> >> The thing with PON is that every time the light hits a splitter it loses >> a bit of strength, so you sort of have to plan to use a little hotter SFP >> in your OLT sometimes. Luckily, those are getting way cheaper nowadays, so >> it’s not the end of the world, but you do have to plan for that. >> >> >> >> Plus, each splice you do cuts down the signal a bit more. Fusion splicers >> only lose a tiny bit, but a physical connector can lose a bunch more, like >> the equivalent of a mile or more of distance, and a piece of crud on an >> uncleaned connector can lose 5 miles distance, so make sure you clean them >> with those cheap cleaner tools. >> >> >> >> On Aug 18, 2025, at 8:39 AM, Josh Luthman <[email protected]> >> wrote: >> >> >> >> Splitters are waaay small. Smaller than a standard house key. >> >> >> >> What you are looking at is an MST terminal, looks like 8 ports. There >> can be a splitter inside of that yes. You can have the MST with 8 fibers >> splice to another 8 fibers or you can have what is in your picture have 1 >> fiber in, split 1x8, and then have 8 ports out for the installers to simply >> plug in to. >> >> >> >> If that MST is a 1x8, you can have a 1x4 before it, between the MST and >> OLT. That makes for OLT -> 1x4 splitter -> 1x8 splitter/MST. That is >> still a 1x32 split. >> >> >> >> On Mon, Aug 18, 2025 at 11:34 AM Ken Hohhof <[email protected]> wrote: >> >> I thought PON used like 16:1 or 32:1 splitters, and in this photo, I >> assumed that’s what the black boxes were. >> >> >> >> *From:* AF <[email protected]> *On Behalf Of *Josh Luthman >> *Sent:* Monday, August 18, 2025 10:16 AM >> *To:* AnimalFarm Microwave Users Group <[email protected]> >> *Subject:* Re: [AFMUG] how is underground FTTH done? >> >> >> >> Don't assume that about aerial. That's not how it works. Don't think >> about it in terms of taps. >> >> >> >> Generally speaking, installations are PON. What we do is design the >> fiber so we can hook up 100% of homes. We assign a color to every house. >> >> >> >> The first thing to think about is that you have to access the individual >> strand out of the cable, be it 12/24/48/144/etc. That is done with a >> SpliceCase or you splice on an MST for an ez mode plug. At Imagine we only >> splice - no connectors, no MST, no plugs, etc. >> >> >> Second thing is that when there's a cable up and down the road, you just >> need access to it through the case/MST from the house. This can be from >> the house to the handhole (concrete box in the ground) or you can run it >> from the house to the handhole through some 1.25" duct to the next handhole >> where there is one case. >> >> >> >> I can show you what it looks like if you don't get it yet. >> >> >> >> On Mon, Aug 18, 2025 at 11:11 AM Ken Hohhof <[email protected]> wrote: >> >> The fiber train left without me, so maybe someone here can help me >> understand how the physical installation is typically done. >> >> >> >> I’ve seen aerial fiber and it’s pretty straightforward, I see splitters >> up on poles maybe at each intersection, and to hook up a customer, they run >> a drop wire from the nearest splitter to the house. If take rate is better >> than expected or a new house is built, worst case I assume they just add a >> splitter. >> >> >> >> But I also see FTTH deployments going in where they are boring for duct >> in the ROW and putting a little handhole in front of every house. How does >> this work? Are they using taps instead of splitters? If not, when they >> get a customer install order, do they pull his drop cable through all the >> handholes to a splitter? That doesn’t seem feasible. Are they dedicating >> a strand to each house and pulling the main cable out each time and >> splicing to that strand? And what if they estimate the take rate wrong, or >> a new house is built? >> >> >> >> There’s probably a simple explanation and once someone enlightens me it >> will be a Duh! moment. >> >> -- >> AF mailing list >> [email protected] >> http://af.afmug.com/mailman/listinfo/af_af.afmug.com >> >> -- >> AF mailing list >> [email protected] >> http://af.afmug.com/mailman/listinfo/af_af.afmug.com >> >> -- >> AF mailing list >> [email protected] >> http://af.afmug.com/mailman/listinfo/af_af.afmug.com >> >> >> >> -- >> AF mailing list >> [email protected] >> http://af.afmug.com/mailman/listinfo/af_af.afmug.com >> >> -- >> AF mailing list >> [email protected] >> http://af.afmug.com/mailman/listinfo/af_af.afmug.com >> > -- > AF mailing list > [email protected] > http://af.afmug.com/mailman/listinfo/af_af.afmug.com > > -- > AF mailing list > [email protected] > http://af.afmug.com/mailman/listinfo/af_af.afmug.com > > > -- > AF mailing list > [email protected] > http://af.afmug.com/mailman/listinfo/af_af.afmug.com >
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