XS4ALL Fiber

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This page describes some of the technical details of fiber to the home (FttH) in the Netherlands.

With the background information in this article, you can safely connect fiber directly to your own router.

Fiber to the Home

The technical details of the fiber connection depend on the area were you live. In my case, the fiber to the home (FttH) connection was created by Reggefiber (part of KPN) in 2018. Reggefiber choose point-to-point Ethernet connections as the technology (sometime called active optical networks, AON), meaning there is a direct fiber from each home to the neighbourhood node (glasvezelwijkcentrale) (technical term: to the Optical Line Terminals, OLT).

Background: Your situation may be different. In Europe, point-to-point Ethernet connections are most popular, but worldwide (mostly Asia and America) Passive Optical Networks (PON) technologies are more popular, either Ethernet PON (EPON) or Gigabit PON (GPON). There may be FttH operators in the Netherlands who have chosen PON as well. Note that the names EPON and GPON may be confusing: both EPON and GPON carry Gigabit Ethernet. The main difference is that in PON networks, multiple households use the same fiber, so it is slightly cheaper to install. This also means that households share the bandwidth, using time division mulitplexing (TDM) techniques. The main advantage of point-to-point connections is that it is possible to upgrade a single household to e.g. 10 Gbit/s. For PON, the whole neighbourhood needs new equipment. As a consumer, I prefer point-to-point Ethernet connections.

Fiber Terminal

The fiber connection is terminated in your house, usually in the meter cupboard, at a Fiber Termination Unit (FTU). The FTU is the passive part. The FTU is constructed so that an active module can be connected on top of it. This active part is the Network Termination Unit (NTU), sometimes called Optical Network Terminal (ONT). The NTU may contain a fiber modem.

What is used will depend on your provider and fiber operator. For example, in my previous household, the NTU was a modem that split the Internet, television and telephony signals, and I had to connect the modem to a router with a UTP cable. In my current household I use either XS4ALL or Freedom Internet. Neither provider does not use such a modem. Instead, they extend the optical fiber to a different device, the Fritz!box 5490, which functions as a modem, router, wifi basestation and telephony basestation all-in-one. These all-in-one devices are called Integrated Access Device (IAD).

Background: Some older fiber terminals (installed before ~2015) contain two fibers. In that case, one fiber carried VLANs for Internet, telephony and interactive television, while the other fiber carried non-interactive television. This non-interactive television was converted to a digital video broadcasting over coax signal (DVB-C) at the fiber modem. As far as I know the last internet provider that offered this technology pulled the plug in 2019, and the second fiber to your home is completely unused. If you really want a DVB-C signal (because your house only has coax cables and no UTP cables), XS4ALL is selling a Teleste coax-adapter for television in the XS4ALL webshop, but frankly, I would replace the coax cable with UTP in your house.

Physical Connector and Optics

So you want to replace the Fritz!box with your own device, like a Ubiquiti router.

That possible! But you will note that the optical fiber that is plugged into the Fritz!box can't be plugged in to your own device.

You'll need two things, an optic and a fiber.

First of all the optic: your device will most likely has a SFP, SFP+ or even SFP28 port. Both are small slots in which you can plug an optical transceiver module ("optic" or "transceiver" for short. Transceiver is a portmanteau of transponder and receiver). The only difference between the three is that SFP can only carry 1 Gbit/s modules, while SFP+ ports can carry either 1 Gbit/s or 10 Gbit/s modules, and SFP28 can carry 25 Gbit/s (28 Gbit/s if you include overhead, hence the name). All three have the same form factor. There are other form factors beside SFP, like GBICs (larger, old-fashioned 1 Gbit/s modules) or QSFP modules (quadruple SFP for 4×10 = 40 Gbit/s, or 4×25 = 100 Gb/s).

Most transceivers have two fibers: one for each direction (sending and receiving data). In this case, you need a "BiDi" optic, where a single fibre carried data both ways (bidirectional, hence the name), each with a different wavelength (different colour of light). The downlink to your home is 1490 nm, the uplink to the OLT in the neighbourhood node is 1310 nm. So at home you need a 1000BASE-BX BiDi SFP 1310nm-TX/1490nm-RX 20km DOM Transceiver Module (1000 base = 1 Gb/s; BX = bidi) to connect the fiber coming in your home. If -for whatever reason- you still like to connect the fiber interface of the Fritz!Box, you need the reverse optics (1490nm-RX/1310-TX). Note that there are many variants, for different power levels (10 km, 20km, 40km) and different wavelength. Another common optic is BiDi SFP 1310nm-TX/1550nm-RX. Most likely, this will work as well: most receivers accept a broad range of wavelengths.

Secondly, you need a new fibre. The connector on the Fritz!box is a SC connector, while SPF modules use a smaller LC connector. So the fiber that XS4ALL gave you has the wrong connector. The side on the ONT will have a SC connector, but beware: most likely it will be a green connector, rather than blue. Blue connectors are Ultra Physical Contact (SC/PC or SC/UPC), while green connectors are Angled Physical Contact (SC/APC). At UPC connectors, the fiber has a straight cut, while at APC connectors, the fiber is cut at an angle. The angle prevents reflections of light. You should not connect a SC/UPC connector to a SC/APC connector, there will be air between the contacts, and you will have at least 50% (3 dB) loss of power. It might work (the power budget of optics is typically >10 dB), but it is error-prone. Your fiber must must carry 1310-1500 nm light, so you need the (slight more expensive) single mode fiber, which has a core diameter of about 9 µm. The alternative of multimode fiber, which has a core diameter of about 50 µm, can only carry light at about 850 nm, and will only reach a few hundred meters. Not enough to carry light to the neighbourhood node. You can easily tell single mode apart from multimode because the single mode fiber is always yellow, while multimode fiber is gray, orange, aqua, or lime green, depending on the specification (OM1, OM2, OM3, OM4 or OM5), Single mode fiber also comes in multiple specifications: OS1 or OS2, but both are yellow. Thankfully, it does not matter which of these two (OS1 or OS2) you choose for a short patch cable. In short, you need a single mode fiber with a SC/APC connector on one end, and a plain LC (LC/UPC) connector on the other end.

For both optic and fiber, I recommend buying from the Chinese fiberstore, fs.com. For the fiber, you need to select the Customised Simplex Single Mode Fibre Patch. FS ships from their German warehouse, so no import-duty surprises. The only disadvantages is that a customised fiber patch takes 2-3 weeks to make. However, I'm not aware of a faster option. Most importantly though, is that fs.com is about 3-10 times cheaper compared to other (professional) resellers, who rarely ship to consumers. Interestingly enough, the optics of FS.com come from the same plants as those create by professional companies (like Cisco and Juniper). There is a difference in quality though: at plants, all optics are tested, and those that are easily within specs get shipped to these larger companies and are sold at a premium price, while the optics that are barely in specs are sold by fs.com at a discount price. In practice, you don't need those premium optics for 1 Gbit/s (or even 10 Gbit/s) optics. Only for 100 Gbit/s optics, it may pay off to choose premium optics, since there are much more error prone compared to 1 or 10 Gbit/s optics.


XS4ALL uses the standard KPN backbone, meaning they also carry the same three VLANs as KPN does with FttH:

VLAN Usage Used by XS4ALL?
4 Television yes
6 Internet yes
7 Telephony only for standard phone, not for VoIP

Note that VLAN 6 is used for television, even if you no longer need to create a separate network for television in your home.

This section is unfinished.

A Note on UTP

Finally, a small note if you want to install UTP backbone in your house. You might be tempted to install Cat 6 or even Cat 8 in your home, because that supposedly is required for 10 Gbit/s.

I don't think that's needed. According to the specs, Cat 5e can also carry 10 Gbit/s, just not the full 100 meter, but "merely" up to 45 meters. Your house is most likely not that big. Cat 6 is more bulky and has a plastic "cross bar" making it harder to pull cables. If you want quality, I would recommend using better shielding. I used U/FTP (the systematic name for STP) and earthed all equipment. In addition, make sure to use UTP with solid core for fixed (backbone) cables, and only use stranded wires for flexible patch cables. Just like you should do installing electrical wires in your home. Finally, if you care for higher quality, look for solid copper cables, instead of copper-cladded aluminium (CCA). Electrically, CCA is just as good as solid copper, but it may be a tell-tale for higher quality cables in general.

For more details, see the page on Copper cable.