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Electrical and Computer Engineering

Lightwave Systems Research Laboratory

Activities

Signal Processing

constellation

The realization of suitable high-speed digital-to-analog converters, analog-to-digital converters, and digital signal processors has allowed advanced signal processing to offer substantial improvements in the performance and functionality of fiber-optic communication systems. In the transmitter, appropriate drive signals for an optical modulator are synthesized using digital signal processing and digital-to-analog conversion. This permits the generation of modulated optical signals with unprecedented control of the time-varying amplitude and phase. The transmitted signal can be pre-compensated to account for fiber dispersion, fiber nonlinear effects, and the filtering of reconfigurable optical add-drop multiplexers. In the receiver, the combination of coherent detection, analog-to-digital conversion, and digital signal processing is a particularly powerful approach. Coherent detection preserves both the amplitude and phase of the received optical signal in the photo-detected signal. This allows for post-compensation using digital signal processing that effectively mitigates linear transmission impairments and implements key receiver functions.

Topics currently being investigated include the following:

  • pre-compensation for spectrally efficient modulation formats,

  • pre-compensation for directly modulated lasers, and

  • signal processing for digital coherent systems.