Observation of coherent interchannel interference in the multiwavelength operation of an acoustooptic filter

Wavelength-division multiplexing using acoustically tuned optical filters offers narrow channel spacing, wide tuning range, and the capability for multiple-wavelength switching. It is shown that a coherent source of interference can arise in multiwavelength switching, due to the simultaneous interaction of several acoustic waves with even a single optical channel. Bit-error-rate studies have been performed on an integrated-optic version of the acoustooptic filter and a crosstalk penalty of approximately 2 dB due to dual channel interference has been observed. The theoretical origin of this crosstalk is described and it is shown that a modest relaxation of channel spacing can effectively eliminate and crosstalk penalty.>