Improvement of NRZ based 40 Gbit/s single channel and WDM transmission using pre-chirp

Chirped NRZ (nCRZ) modulation format has been presented for single channel and WDM 40 Gbit/s transmission. The transmission properties of cNRZ are compared with conventional NRZ and RZ signals and analysed by means of numerical simulations. It was shown that an appropriate pre-chirping through phase modulation can improve the nonlinear characteristics and maximum transmission length in NRZ based transmission systems over standard single mode fiber (SSMF). The results confirmed that the use of a cNRZ form reduces the self phase modulation-group velocity dispersion (SPM-GVD) impairments in SSMF compared to NRZ and RZ signal forms.