ABSTRACT
Digital signal processing (DSP) is the principal functionality of modern optical communication systems employed at both the coherent optical receivers and the transmitter. At the transmitter, DSP is employed for determining the pulse shape at the output of optical modulators, as compensation for the limited bandwidth of the digital-to-analog converter (DAC), as well as that of the transfer characteristics of the electro-optic external modulators, and deskewing of the electrical path differences between the in-phase and quadrature-phase signals that often occur in ultra-high-speed systems. It is noted that the mixing of the received signals and the local oscillator (LO) laser happens in the photodetection stage.
