Noise tolerance in wavelength-selective switching of optical DQPSK pulse train by collinear acoustooptic devices

Optical switching of high-bit-rate QPSK pulse trains using collinear acoustooptic (AO) devices is theoretically discussed. Since the collinear AO devices have wavelength selectivity, the switched optical pulse trains suffer from distortion when the bandwidth of the pulse train is comparable to the pass bandwidth of the AO device. As the AO device, a sidelobe-suppressed device with a tapered surface-acoustic-wave (SAW) waveguide and a Butterworth-type filter device with a lossy SAW directional coupler are considered. Phase distortion of optical pulse trains at 40 to 100 G symbol/s in quadrature phase-shift-keying format is numerically analyzed.