Optical low coherence method for characterizing silica-based arrayed-waveguide grating multiplexers

We describe a powerful method for the precise measurement of optical path phase errors and power-distribution coefficients in silica-based arrayed-waveguide grating multiplexers through the use of Fourier transform spectroscopy. The theoretical accuracies for measuring these parameters are /spl plusmn/1/spl deg/ and /spl plusmn/5%, respectively, when the geometrical step increment of the arrayed waveguides is greater than 48 /spl mu/m. The method reveals the random distributions of optical path phase errors in two multiplexers with channel spacings of 100 and 10 GHz, and proves that these distributions are the main origins of the channel crosstalk. The method predicts that when optical path phase errors are sufficiently reduced, the channel crosstalk values will decrease to -39 and -29 dB, respectively, and these limits are due to slightly deformed power distributions.