The entire IT industry is packed with mathematics. So instead of keeping things easy we need to work our way around imposed restriction that have been imposed on us by history.
When hardware was developed 1 to 5 decades ago things were (maybe still are) very expensive. Every corner was cut to keep costs low in order to be to sell anything. You can have the latest and greatest but if you’re pricing yourself out of the market the shelf-life of your shares becomes very short and at some stage you basically cease to exist. Companies like DEC and SUN have found out the hard way. Fabulous marvels of engineering but lack of sales and marketing efforts aligned to that engineering feat basically failed to gain sufficient traction in the market and as such they are no more.
Going back to the hardware restrictions and the SFP -INF state
You may encounter some output from an sfpshow (Brocade) or “show transceiver detail” (Cisco) like this:
Temperature: 46 Centigrade
Current: 6.428 mAmps
Voltage: 3261.5 mVolts
RX Power: -inf dBm (0.0 uW)
TX Power: -3.3 dBm (464.2 uW)
So what does that mean? Read on.