This is an ISOLAN converter for AUI to a Fibre uplink. The 15 Pin AUI connects to a local workstation and the fibre links back towards to core. It is powered via the AUI port from the PC.

Internally, this unit PCB is built by BICC. The optical output is a red LED rather than a laser. The receiver is sheilded by the cover visible, this is not removeable easily so I didn't do a picture.