My Internet provider just installed a 2,5/1Gbps Internet connection and I’ve asked the guys to run a couple of their fiber to connect my router (HP Prodesk with OPNsense) to my server. I didn’t know that the fiber is single mode and all the SFP+ sold used now seems to be all for multi mode fiber (www.bargainhardware.co.ukfor example). The cable is about 30m, can I use a 810nm SFP+ or is it definitely better to use a 1310nm?
You got it right! On the cable unfortunately there is no wavelength printed (it’s a cable made for my ISP), but I’ve read on a forum (that talks about this ISP):
I think that I’ll go with 2 SFP+ 10GBASE-LRM 1310nm 2km Module, Cisco that costs 29€
Edit: In the meanwhile, do you have any 2,5Gbe PCI card that you suggest (I need it to connect OPNsense to the ONT via PPPoE)? I’ve found only the QNAP QXG-2G1T-I225 that costs about 75€ or the Edimax EN-9225TX-E for about 41€ (but I haven’t read much about this one).
In my first draft of an answer, I thought about mentioning GPON but then forgot. But now that you mention it, can you describe if the fibres they installed are terminated individually, or are paired up?
GPON uses just a single fibre for an entire neighborhood, whereas connectivity between servers uses two fibres, which are paired together as a single cable. The exception is for “bidirectional” xcvrs, which like GPON use just one fibre, but these are more of a stopgap than something voluntarily chosen.
Fortunately, two separate fibres can be paired together to operate as if they were part of the same cable; this is exactly why the LC and SC connectors come in a duplex (aka side-by-side) format.
But if the ISP does GPON, they may have terminated your internal fibre run using SC, which is very common in that industry. But there’s a thing with GPON specifically, where the industry has moved to polishing the fiber connector ends with an angle, known as Angled Physical Contact (APC) and marked with green connectors, versus the older Ultra Physical Contact (UPC) that has no angle. The benefit of APC is to reduce losses in the ISP’s fibre plant, which helps improve services.
Whereas in data center and networking, I have never seen anything but UPC, and that’s what xcvrs will expect, with tiny exceptions or if they’re GPON xcvrs.
So I need to correct my previous statement: to be fully functional as designed, the fiber and xcvr must match all of: wavelength, mode, connector, and the connector’s polish.
The good news is that this should mostly be moot for your 30 meter run, since the extra losses from mismatched polish should still link up.
As for that xcvr, please note that it’s an LRM, or Long Range Multimode xcvr. Would it probably work at 30 meters? Probably. But an LR xcvr that is single mode 1310 nm would be ideal.
Thanks for your precision! To the ONT arrives a single fiber with a SC/APC connector, but this is not a problem since I will be using the ONT provided and use the 2,5Gb copper port to connect it to OPNsense (looking for a 2,5 Gb PCI card). The 2 fiber that I’ve asked them to run (from OPNsense to server) are terminated with the same SC/APC connectors and I was thinking about using this SC female/female adapter and this SC/APC to LC cable that I’ve just realized that are still APC…I’ll have a look if there are SC/APC to LC/UPC cables
Is it a LRM? Damn, I didn’t realized since I’ve filtered for single mode. If the filter doesn’t work, I’ve no idea which is LR. Would you be so gentle to point to a cheap one for single mode finer?
I’ve only looked briefly into APC/UPC adapters, although my intention was to do the opposite of your scenario. In my case, I already had LC/UPC terminated duplex fibre through the house, and I want to use it to move my ISP’s ONT closer to my networking closet. That requires me to convert the ISP’s SC/APC to LC/UPC at the current terminus, then convert it back in my wiring closet. I hadn’t gotten past the planning stage for that move, though.
Although your ISP was kind enough to run this fibre for you, the price of 30 meters LC/UPC terminated fibre isn’t terribly excessive (at least here in USA), so would it be possible to use their fibre as a pull-string to run new fibre instead? That would avoid all the adapters, although you’d have to be handy and careful with the pull forces allowed on a fibre.
But I digress. On the xcvr choice, I don’t have any recommendations, as I’m on mobile. But one avenue is to look at a reputable switch manufacturer and find their xcvr list. The big manufacturers (Cisco, HPE/Aruba, etc) will have detailed spec sheets, so you can find the branded one that works for you. And then you can cross-reference that to cheaper, generic, compatible xcvrs.
The problem is the installation of the connectors. They’ve welded the fiber the SC/APC pigtails, I wouldn’t be able to do that.
That would be very very generous of you; in the fiber section I’m pretty ignorant and I’m worried to purchase wrong items 🙈
I quickly looked up the HPE/Aruba transceiver document, and starting on page 61 is the table of SFP+ transceivers, specifically describing the frequency and mode. At least from their transceivers, J9151A, J9151E, JL749A, and JL783A would work for your single-mode, 1310 nm needs.
You will have to do additional research to find generic parts which are equivalent to those transceivers. Good luck in your endeavors!
Thanks a lot! It seems that this from fs.com in the non Aruba compatible brands costs 32€ Thanks again!
Edit: And I’ve even found the LC/UPC to SC/APC cable!
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Re: 2.5 Gbps PCIe card
In some ways, I kinda despise the 802.3bz specification for 2.5 and 5 Gbps on twisted pair. It came into existence after 10 Gbps twisted-pair was standardized, and IMO exists only as a reaction to the stubbornly high price of 10 Gbps ports and the lack of adoption – 1000 Mbps has been a mainstay and is often more than sufficient.
802.3bz is only defined for twisted pair and not fibre. So there aren’t too many xcvrs that support it, and even fewer SFP+ ports will accept such xcvrs. As a result, the cheap route of buying an SFP+ card and a compatible xcvr is essentially off-the-table.
The only 802.3bz compatible PCIe card I’ve ever personally used is an Aquantia AQN-107 that I bought on sale in 2017. It has excellent support in Linux, and did do 10 Gbps line rate by my testing.
That said, I can’t imagine that cards that do only 2.5 Gbps would somehow be less performant. 2.5 Gbps hardware is finding its way into gaming motherboards, so I would think the chips are mature enough that you can just buy any NIC and expect it to work, just like buying a 1000 Mbps NIC.
BTW, some of these 802.3bz NICs will eschew 10/100 Mbps support, because of the complexity of retaining that backwards compatibility. This is almost inconsequential in 2024, but I thought I’d mention it.