Kohei Mandai

Incoherent 32-Level Optical Multilevel Signaling Technologies

In order to explore the potential of optical multilevel signaling for high-speed optical fiber networks, an incoherent 50 Gbit/s 32-level optical multilevel signaling (combination of QASK and 8-DPSK) is demonstrated, for the first time. The application of an ISI-suppressed modulation technique, an orthogonally-coupled differential detection technique and the digital signal processing technique have also been proposed and verified to enhance the performance of multilevel signaling. A 100-km dispersion shifted fiber transmission has also been performed, and the degradation via optical fiber nonlinear effect, self-phase modulation (SPM), is observed. The receiver side simple digital cancellation technique of the SPM-induced phase shift is also proposed and experimentally demonstrated with more than 6.8 dB increase of fiber input power.

Experimental Demonstration of Incoherent Optical Multilevel Staggered-APSK (Amplitude- and Phase-Shift Keying) Signaling

Generation and incoherent detection of a 30-Gbit/s 8-level staggered APSK signal using two-state MLSE detection is successfully demonstrated with a 140-km fiber transmission. Its better constellation design results in 1.5-dB sensitivity improvement from 8-DPSK signaling.

Advanced Multi-level Transmission Systems

Multi-level transmission having advantage of wider dispersion tolerance and narrower bandwidth, is one of the strong candidate for ultra high-speed serial interface. We review recent progress in multi-level systems, especially, incoherent multi-level receiver.