With a 1:n device, in one direction they split the signal into n ports/fibers and into the other end they combine the signals into one port/fiber. Unlike active devices (which require power), splitters operate without electricity, relying solely on the physics of. For example, optical splitters send light to many output ports. You can also use them to join light from different sources into one output. This helps with signal grouping. 8:8 with 8 inputs and 8 outputs, which are used to create networks with n devices, like 8 in this case, allowing all devices to talk to each other.