Reduction of optical-beat interference in subcarrier networks

We present a method for improving the performance of a subcarrier multiplexed passive optical network (SCM-PON) in the presence of optical beat interference (OBI). By introducing strong "clipping tones" (optical-modulation depth >1) on each of the lasers their optical spectrum can be broadened, thereby ameliorating the effects of OBI. By carefully selecting the RF band used to carry signals, and that used for "clipping tones", OBI can be reduced without the clipping inducing errors. We have demonstrated the effectiveness of this technique by measuring the BER of a QPSK channel in the presence of OBI. A delayed self-homodyne technique was used to simulate worst-case conditions.