Electronic equalization for advanced Modulation formats in dispersion-limited systems

We investigate in this letter the use of electronic equalization on dispersion-limited systems for different modulation formats. Besides analyzing equalization on standard nonreturn-to-zero (NRZ) intensity modulation as a reference, we focus on two advanced modulation formats, duobinary (DB) and differential phase-shift keying (DPSK) which are recently gaining a lot of attention. We demonstrate that the introduction of an electronic equalizer strongly improves standard NRZ performance, whereas, it has a limited effect on DB and DPSK formats. Moreover, we give rules for the optimal choice of the equalizer transversal filter parameters, i.e., the number of taps and the delay between taps.