Wide-Temperature-Range (25–80 °C) 53-Gbaud PAM4 (106-Gb/s) Operation of 1.3- μ m Directly Modulated DFB Lasers for 10-km Transmission

A 1.3- μ m directly modulated distributed feedback laser was newly developed by adopting an asymmetric corrugation pitch modulated grating structure and an InGaAlAs multiquantum well active layer with both a high optical confinement factor and a high differential gain. A low threshold current and a large saturation current in light-current characteristics at high temperature were obtained and a high 3-dB bandwidth and a high relaxation oscillation frequency in electro-optical characteristics were also achieved over a wide temperature range. As a result, clear back-to-back eye openings were achieved for 26-Gbaud PAM4 (53-Gb/s) operation from 25 to 95 °C with large outer extinction ratio and sufficiently small transmission dispersion eye closure quaternary. Furthermore, 53-Gbaud PAM4 (106-Gb/s) operation from 25 to 80 °C was successfully demonstrated for both back-to-back and after 10-km single mode fiber transmission. These excellent characteristics make our DFB laser a promising cost-effective and compact transceiver with low power consumption for next-generation 400GbE applications.