Effects of power truncation on the insertion loss and crosstalk

A measurement of the insertion loss and crosstalk in folded, 100 GHz, arrayed waveguide multiplexers as a function of the number of grating waveguides is described. The number of grating waveguides can be varied in a single device to evaluate power truncation effects with high accuracy. We show that the central peak insertion loss decreases exponentially with the number of grating waveguides. The crosstalk decreases with increased number of waveguides and the measured dependence shows valleys and peaks associated with the passband spectrum of individual channels. These observations are in good agreement with simulation results. With the arrayed waveguide design used in this work the crosstalk performance becomes phase error limited for the number of waveguides greater than 250.