According our statistics, Single Family Unit’s, or SFU’s are most popular EPON ONU‘s ordered and shipped worldwide, and it really does not depends on a market or country. Of course, types of SFU’s vary.
For example as one classifier, SFU’s can be divided in Indoor Type ONU’s, or in Outdoor type. If we look at various business models used by FTTx operators worldwide, then we can see that SFU can be counted as a part of telecommunications network, and thus owned by operator who offers a service to an enduser (or owned by an Open Access Network provider, but that is a bit different scenario), or it can be considered also as CPE equipment, and owned by subscriber.
Simplest ONU one can think of, is shown below:
Figure 1: SFU EPON ONU type. Connects one house and are installed in one single family house
So, it’s basically a bridge, Layer 2 equipment, which does not offers routing functions, wifi functionality and usually is installed at customers house somewhere on a wall or under ceilings.
Or, it can also be installed outdoors, but concept will remain same. Outdoor ONU will look like this:
Figure 2: Outdoor (waterproof) SFU EPON ONU type. Connects one house and are installed in one single family house. As this unit have 4 Ethernet ports it can connect up to 4 houses as well.
Now, in case customer own’s CPE unit, and some countries have regulations, then we can consider demarcation point to be located between drop fiber and customers home network. It is nowadays almost 100 % sure, that at customer homes will be more than one PC using internet same time, not talking about smartphones, tablet PC’s and notebooks, so you can consider that customers will plug in SFU a WiFi NAT home routers instead of directly plugging in PC’s.
In case operator is offering also IPTV services, then 1 port SFU smallest EPON ONU’s might not be the best choice, and in this case or above depicted 4 Gigabit Ethernet Outdoor ONU is a good choice, or 4 Fast Ethernet port EPON ONU like this:
Figure 3: SFU EPON ONU type with 4 Fast Ethernet ports.
Now, it might be not so obvious first, why would you need more than 2 ports to connect a single family house, however, if you consider that 1 port already will be definitely used by WiFi NAT router which will distribute internet over customers house, and another port – for IPTV set top boxes, then more 2 ports can be used for example for connecting IP Phone, and the the left one – some Smart Home system or Security Monitoring.
And here we are coming to next type of SFU ONU, which is a next step after above 4 Ethernet type SFU – 4 Ethernet and 2 Voice ports SFU ONU, and it might look like this:
Figure 4: SFU EPON ONU type with 4 Fast Ethernet ports and 2 FXS (SIP) ports
And here, besides the flexibility you can get with 4 universal Ethernet ports, there is also 2 FXS type SIP based ports, where regular (not IP phone!) can be connected. So, it will be already so called double play SFU (similar to more popular expression – Triple Play ONU). However, again it’s all terms, and in case you use one of ports for IPTV set top box here, then this type of SFU also becomes a Triple Play, so, that operator who chooses this type of ONU can already start offer Triple Play service as a package right away.
If we talk about “real” triple play ONU, which really have all 3 types services or ports on the unit directly, then as an example this SFU type ONU can be mentioned:
Notice the CATV port at the right side of the unit – that will be then a regular CATV type connection to customers TV. Having said that, we need to emphasize that lions share of new FTTx networks installed worldwide will go for IPTV, and thus, pure Ethernet type access SFU’s (or with 2 FXS’s ports) might be a choice to consider for those, who are in planning phase now, and are considering with what type of ONU – SFU go.
SFU’s also can include full residential gateway (sometimes called Home Gateway (HG)) with firewall, NAT router – which then eliminates a need for a subscriber to install it’s own WiFi router to distribute internet in home or office, DHCP server, USB ports, storage or print server and more. This form of SFU then requires a customer cooperation to manage and configure it and thus more support personnel will be required from a operator side. For this, also TR-69 standard must be supported by SFU Home Gateway units.
