Small Business Unit ONU (SBU)
You can get in the situation when more POTS ports than 2 (like for this HGU type ONU) are needed. That could be a small office customer or building with more flats. It may also support a few TDM (time division multiplex) services such as DS1 or E1, via pseudowire emulation. This SBU from Fiberbit:
For example can have 16 FXS POTS ports and if needed same ONU can have also 16 Ethernett ports. Now that’s already SBU MDU type ONU that can connect small office. Then there is also a cellular backhaul unit (CBU) – which is a kind of variation of SBU – or maybe even we can use this term as a new category.
This can be used to send traffic from core network to radio mobile base stations. Legacy mobile networks, those that yet are present and will be present yet for some time in future requires DS1 or E1 service. Of course, this all is migrating to all Ethernet and over IP concepts, but still many of E1′s still exist.
Another variation of SBU ONU is Multitenant unit – MTU, which then also can be shared by several small businesses or many smaller flats. That can be used for example in small resorts or islands like those in Maldives for example. Important function of MTU which makes it different from SBU is a possibility to isolate services from each other, as for a traffic as and as for terms of SLA’s – customers should not “see” each other, there should be no bridge function, so these ONU’s can not be just simple switches – ports must have more logical SLA and traffic separatation that should be managed for each port separately.
You can check example for SBU ONU from Fiberbit here: http://fiberbit.com.tw/products/epon-onu/16-pots-fxs-onu/
