Fiber connection between two buildings
Solvedbrupala Posted messages 111943 Registration date Status Membre Last intervention -
Hello,
I'm starting the installation of fiber optics to connect two buildings 200m apart. I struggled to find precise and accessible information for beginners. I'm here to share my findings. Surely, some pros will chime in to complement or correct me.
The first difficulty, compared to copper networks, is the variety of modes and connectors.
There are two modes: single-mode and multi-mode. As for connectors, it seems there are two that interest us, amateurs: LC and SC. The connectors suit both modes, but not the fibers.
In addition to a cable and connectors, you need either a transceiver that plugs directly into the switch or a media converter (fiber <==> copper).
A. The modes
You need to start by choosing a mode:
- Single-mode: carries further, costs more. Also called OS (S for simplex). Several protocols: OS/1, OS/2, etc.
- Multi-mode: it's the opposite (OM, M for multi). To connect two buildings less than 300m apart, it seems like the right choice. OM/3 allows for a speed of 10Gbs.
The mode affects the entire chain: transceivers, fibers, and connectors.
B. The transceivers and media converters
- If you have a switch capable of optical communication, you need the right transceiver: it's a small box that fits into the switch and connects to the fiber on the other end. The lamp that emits light is located inside this transceiver.
It needs to be the right brand and mode. I don't think there are any other constraints as long as the same two are on each side. - If you don't have such a switch, you can buy a media converter: you plug in the fiber on one side and an RJ45 cable on the other. You need the right mode.
C. The connectors
- SC is larger, cheaper.
- LC is smaller, more expensive.
I chose SC for the linking cable (cheaper) but LC for the transceiver (somewhat by default). I took SC to put on both ends of the cable, SC-SC wall penetrations, and SC-LC patch cords.
Caution: all this equipment must be of the correct mode.
D. The fiber itself
Besides the two modes, you need to choose the right protocol: OM/3 or OM/4, etc.
There's also the diameter. This is especially relevant for connectors. I took 900 microns.
You can find fibers for indoor or outdoor use, aerial or underground.
When assembling, be careful with the bend radius: a copper cable tolerates rather tight bends, pretty much as long as you don't break the copper.
While each fiber has a specific bend radius it can tolerate. For example, for the one I'm targeting, it's 5 centimeters. This needs to be considered when purchasing conduits.
E. The assembly
I haven't started. This is where I expect the second difficulty. I will update my message after I gain some experience. Here's the state of my thoughts:
- The crimping assembly is reserved for pros due to the cost of the machine and the demands of the techniques. Same for soldering.
- You can find pre-assembled options, but they are inevitably difficult to fit into conduits.
- Finally, there are quick connectors or job site connectors. This time, there are tutorials available online.
Your advice is welcome!
2 réponses
Hello,
great summary, a few clarifications:
In the past, multimode fiber was cheaper than single-mode fiber, but that’s not really the case anymore; with the widespread FTTH, prices for single-mode have dropped significantly and often costs less than multimode.
Single-mode fiber is more practical and doesn’t require an attenuator for short distances, and it generally tolerates bends better.
What you call a transceiver or box is called SFP for 1 Gbit/s, SFP+ for 10G, QSFP+, QSFP28 for beyond....
You therefore need a switch that has the appropriate SFP ports. On the switch side, the connectors will be LC for both transmitting and receiving (2 fibers) or a bidirectional SFP+, two SC connectors won't fit on an SFP port. There are also FTTH bidi types, but they are more reserved for operators.
There are two types of SC connectors: SC/APC (angled polish) or SC/UPC (flat polish); most of the time, we use SC/APC (green), while SC/UPC are blue (hello Freebox).
"The lamp that emits the light is located inside.
It must be from the right brand and the right mode."
The lamp in question is a laser and the light is invisible (infrared); bidi SFPs have two wavelengths, one for each direction, and they need to be complementary (one's transmission = the other's reception) facing each other.
I recommend using factory-terminated patch cords or pre-connectorized cables (see my link at the beginning) if you don’t have the tools to splice in the field.
As with copper, we do not connect two ports directly; we go through a patch panel with jumpers and finish with a small patch cord to the port to be connected.
And there you go, voilà ....
But goodness, how annoying these line breaks are!!
It works!
Construction update:
I failed to install optical sockets.
I fell back on pre-assembled custom cables from fs.com. Excellent company, the price-to-quality ratio is outstanding. And it turned out to be twice as cheap as my previous project.
I stuck with single mode, but with LC connectors so it would fit in my conduits. And with 3mm protection to withstand the treatment: 100m in plastic conduit that has seen mud, with junctions every 25m, but also 100m in a concrete pipe.
I stepped on it, I bent it once between my knee and the gravel, a loop got stuck... Well, it still works.
So it's been a very good experience.
One silly precision: the setup is in parallel, so the number of intermediate connections doesn’t matter. In my case, there are 5.
Thank you very much for your advice, Brupala.
Single-mode or multi-mode???
Thank you very much Brupala: your answer allows me to confirm, or not, my assumptions.
But it calls into question my fundamental choice of multi-mode. It's true that single-mode is a bit cheaper. For the bends, I feel like it's more a question of model: Brico-Réseau sells Socamont that supports the same radii in single or multi.
Will I be more "standard" if I go with single-mode?
I have HPE switches, a J9565A and a J9981A, marked SFP. Can I put SFP+ in them, do you think?
PS: What is APC, the green connectors?
My single-mode cart, then...
For the transceivers, I would take 10G base LR; 1310nm, 10km. I'm hesitating between QSFPTEK and 10GTek.
If your switches have gigabit ports, they are SFP, not SFP+
Some SFP+ can operate at 1 Gbit/s in an SFP cage (although that's not common), it's usually the other way around, an SFP in an SFP+ cage that can operate.
Yes, you'd be more standard in OS2, but forget about SFP+
for APC/UPC
or even: https://www.ingenova.com/quelle-est-la-difference-entre-les-connecteurs-optiques-upc-et-apc/
Thank you! Without you, I would have made several mistakes...
Your last link is very good. If I had found it earlier, I would have saved a lot of research time.
I love adventure and discovery, but I find fiber much more difficult than copper. I'm diving in and I will come back for feedback.
Fiber is easier than copper in practice, simpler; you put a photometer at the end and see the signal level in the band, which is impossible with copper. However, there are some basics to have in order to build a fiber network, not really a lot of additional things to learn, but a different technology to master, especially since it is evolving more currently. For example, today I am discovering the 1300/1300 SFP+ bidi while I had previously stuck to 1300/1500 (I am referring to the nm of the wavelengths).
It’s true that when a copper connection doesn’t work, 8 wires are involved in 2 sockets...
But the connectors are simpler, I think: you choose a category of cable and use RJ45s.
Bidi, does that mean bidirectional? 1300/1500, does that mean the wavelength is not the same in both directions?
Is Mini-Gbic the same as SFP?
I’m struggling to find HPE SFP single-mode transceivers. I think I’ll go for that.
Thanks for your help, I feel much more at ease.