High Power and High Speed SOA Assisted Extended Reach EADFB Laser (AXEL) for 53-Gbaud PAM4 Fiber-Amplifier-Less 60-km Optical Link

In our article to extend a 100 Gbit/s/λ fiber-amplifier-less optical link with a simple and cost-effective transmission system, we have fabricated an O-band wavelength range (1260-1360 nm) SOA assisted extended reach EADFB laser (AXEL) with a 300-μm-long DFB laser and 85-μm-long SOA. The length of the integrated electroabsorption modulator was set to 125 μm to obtain a section with low parasitic capacitance for high speed operation. The fabricated AXEL transmitter simultaneously achieved both the sufficient modulated light output of 8.9 dBm and an excellent quality eye diagram for a 53-Gbaud PAM4 signal with the TDECQ value of 1.52 dB. We investigated the effect of the integrated SOA on the AXEL's performance and found no significant degradation of the quality of the eye diagram or the bit error rate (BER) characteristics of the 53-Gbaud PAM4 back-to-back configuration, even when the AXEL achieved high modulated light output power. We were also able to extend the 53-Gbaud PAM4 fiber-amplifier-less optical link to 60 km by using the AXEL transmitter and APD receiver, and achieved error-free transmission assuming KP4-forward error collection (FEC). These results demonstrate that the enhanced modulated light output using the AXEL can successfully extend the 53-Gbaud PAM4 reach with a simple transmission setup.