Frequency Domain vs. Time Domain Filter Design of RRC Pulse Shaper for Spectral Confinement in High Speed Optical Communications

Inhalt:
In this work, we present two design methods of the root raised cosine (RRC) pulse shaper in the transmitter of a Nyquist wavelength division multiplexing (WDM) system. Spectral shaping is one of the techniques needed to meet the requirement for high spectral efficiency in high bandwidth applications. A frequency domain (FD) design and a time domain (TD) design of the RRC filter are given and compared based on their length and their spectral shape. The spectral shape of a frequency domain RRC filter desgined with double degrees of freedom as the time domain finite impulse response (FIR) RRC filter has side lobes with less power. Additionally, the root sum squared values of the intersymbol interference (ISI) with an FD design is lower than with a TD FIR design.