High-Output-Power 1358-nm-Wavelength SOA- Integrated EADFB Laser (AXEL) for 25-Gbit/s 100-km Transmissions

We developed a 1358-nm-wavelength semiconductor optical amplifier (SOA)-assisted extended-reach electroabsorption modulator integrated distributed feedback laser (AXEL) as a high-power light source for 25G-class passive optical networks (PONs) to ensure sufficient power margin in the transmitter and extend the transmission reach to 100 km. We investigated the effect of the integrated SOA length on the light output power and modulation performance of the AXEL. We found that there was no significant degradation in modulation performance at 25 Gbit/s even for an AXEL with a 175-μm-long SOA. Using this AXEL chip, we fabricated a transmitter by using a commercially available package. The transmitter attained sufficient modulated light output power of 10. 5 dBm and had a high-quality eye diagram for 25-Gbit/s operation. In addition, we found that the measured chirp parameter of the AXEL transmitter was almost 0. This alleviates the transmission distance limitation due to chromatic dispersion and enables the transmission distance to be extended. The loss budget for 20-km transmission, as determined from the measured bit error rate, was 38.4 dB, which is much larger than the value specified for 25G-EPONs. Moreover, the transmission reach was extended to 100 km for the first time, thanks to the AXEL transmitter's high output power. Finally, the possibility of incorporating the AXEL in 100-Gbit/s-ZR4 (80 km) applications using four wavelength channels was considered. The estimated power penalties using the measured chirp parameter were significantly smaller than the measured penalty for 1358 nm. This suggests that the AXEL can also be used for 100-Gbit/s over 80-km transmissions using four channels in a LAN-WDM grid.