Spectral mode splitting scheme: application to 40-Gbit/s RZ-ASK and RZ-PSK transmission

Abstract

Novel modulation formats have been a key issue in many recent reports on 40-Gbit/s applications. In particular, coherent transmission technologies including the differential phase shift keying (DPSK) format in combination with balanced detection have merited a lot of attention, because of its robustness against fiber nonlinearity induced impairments in DWDM applications. We have proposed several novel transmission formats based on amplitude shift keying technology including carrier suppressed return to zero (CS-RZ) and duo-binary carrier suppressed return to zero (DCS-RZ) formats. We have also proposed CSRZ-DPSK formats based on phase shift keying (PSK). In this paper, we discuss the remarkable relation between these advanced signal formats that can be afforded by using the spectral mode splitting (SMS) scheme. All these modulation formats can be interrelated via the SMS scheme, which transforms one signal format into another via spectral filtering. Furthermore, we discuss the transmission performance of these signal formats and show how to improve their performance by employing the SMS scheme. We can achieve both higher tolerance for fiber dispersion and higher allowable launched optical power by employing the SMS scheme. The SMS scheme also provides us with useful applications such as chromatic dispersion monitoring.