I just want to know how much loss a multimode fiber can have before it does not transfer information or slow down the system? I have tested a 12 core mmof that is about 60m long and i am getting 4.5dB loss.
4.5db of loss is not a lot, but it depends what your transmitter and receivers are. In general, if that 4.5 db of loss puts you below the receiver's threshold, then you'll get loss, if it doesn't, then you won't. If this is just a in-building patch run and that's the loss across the entire span, that should not prevent things from working (but it's not a great patch job, either)