This object reports the local optical transceiver's laser bias current in milliamps for this Ethernet port during the archived historical interval, applicable only when the port's media type is fiber. A historical trend of rising bias current helps the admin confirm when a local optic began aging or degrading, ahead of an eventual failure. For example, if a fiber port failed last week, the admin would review cmEthernetTrafficPortHistoryLBC from the preceding weeks to see if the bias current had been climbing before the failure.