ABSTRACT
Digital signal processing (DSP) is the principal functionality of modern optical communications systems, employed at both the coherent optical receivers and the transmitter. In coherent optical communication systems incorporating DSP, the reception of the transmitted signals is implemented by mixing them with an local oscillator whose frequency is identical or close to equality of the channel carrier, namely homodyne or intradyne techniques, respectively. This chapter demonstrates the effectiveness of maximum likelihood sequence estimation in minimum shift keying (MSK) self-homodyne coherent reception transmission systems when under the influence of linear distortion effects with the MSK modulation scheme. It shows that the equalized constellation would offer a much higher signal-to-noise ratio as compared with that of the nonequalized constellation. The chapter describes an enhanced carrier recovery concept covering large frequency offset (FO) and enabling almost zero residual FO for the V-V carrier phase estimation. It investigates the dispersive effect of optical fiber on the transmission speed of the media.
