Homodyne crosstalk in WDM ring and bus networks

We examine the combined effects of coherent and incoherent crosstalk in wavelength-division multiplexed (WDM) ring and bus networks which use add-drop multiplexers. It is widely understood that incoherent crosstalk in these networks causes a fixed bit-error-rate (BER) door at the receiver. We show that coherent crosstalk causes a range of possible received powers. In combination with incoherent crosstalk, this leads to a range of possible BER floor positions. We use a Monte Carlo simulation to show that when both coherent and incoherent crosstalk are considered, BER floors are likely to be higher than previously appreciated. Satisfactory network performance can be ensured by careful network management, or by reducing component leakage.