This paper describes system and circuit considerations for transmit/receive integrated circuits meeting the requirements of industrial fiber optic data links. The integrated circuits are: TTL compatible, operate with arbitrary data format over the range from d.c. to a maximum NRZ data rate of 15 Mbits/s with a 10-9error rate at a minimum receiver detector current of 125 nA, have >55 dB electrical dynamic range and an automatic link monitor, operate from a single +5 V supply and are temperature and voltage compensated. These circuits utilize an internal pulse bipolar line coding to accommodate an arbitrary input signal format or, by switching a control input, an ON-OFF modulation for zero average TTL input signals operating above 2 Mbit/s data rate.