Abstract

Optical beat interference (OBI) is an impairment in subcarrier- based optical-fiber transmission systems that combine light from two or more lasers in a passive optical network (PON).¹ When lasers operate sufficiently close to each other in wavelength, the beating of these lasers at the detector generates noise in the receiver at a frequency corresponding to the difference in optical wavelengths.^2,3 If this noise overlaps a frequency band in the subcarrier system, OBI can decrease the signal-to-noise ratio (SNR). In this paper we report, for what we believe to be the first time, measurements of the SNR and bit error rate(BER) for a realistic system exhibiting OBI. We show that there is a good correlation between the measured BER floors due to OBI and the SNR measured by a microwave power meter. Finally, we show that the effect of OBI can be significantly reduced by increasing the laser modulation index.

© 1993 Optical Society of America