Linearisation Method of DML-Based Transmitters for Optical Communications Part III: Pulse Amplitude Modulation

A new linearization method for optical transmitters based on directly modulated lasers (DMLs), named the Stretched method, was proposed in Parts I and II of this work. presented theoretical framework non-return-to-zero (NRZ) modulation related detailed simulation experimental results. Here, we extend to pulse amplitude schemes (PAM). Focussing 4-level PAM (PAM-4), present background discuss implementation options. simplified variation generation signals with a significantly lower number sub-currents is proposed. Simulation studies PAM-4 transmission at 50 GBaud (100 Gb/s) an proof-of–principle demonstration 16 (32 are reported 850 nm vertical-cavity surface-emitting (VCSELs). For PAM-4, products effective eye diagram areas ( ${\boldsymbol{PS}}$ ) 0.6 × 10 ?5 43 before after applying were measured, demonstrating improvement ratio ?72. The sensitivity tolerances analyzed using experiment.