The performance of a hybrid AM/BPSK (amplitude modulated/binary phase
shift kaying) polymer optical fibre transmission system has been inves
tigated. A BPSK modulated 2Mbit/s pseudorandom digital channel is subs
tituted for one of the AM channels in a 60-channel cable TV system. Fo
r the digital channel, a bit error rate of < 10(-9) is obtained after
transmission through 200m of fibre. The results show that distortion c
aused by laser nonlinearity did not degrade the system at low modulati
on depth.