Monolithically integrated directly modulated DFB laser array with MMI coupler for 100GBASE-LR4 application

We developed the first 1.3-µm, 4×25-Gbit/s directly modulated DFB laser array monolithically integrated with an MMI coupler suitable for 100GBASE-LR4 application. Error-free operation was achieved for a 30-km SMF transmission when modulating four DMLs simultaneously.

1. Introduction

Compact and cost-effective optical components are needed if we are to increase the capacity and reduce the power consumption of both datacenter and telecom networks to cope with the continuous increase in data traffic. Against this background, 100Gbit Ethernet (100GbE) was standardized in 2010 [1] and 400Gbit Ethernet (400GbE) is now being standardized by an IEEE task force [2]. For 100GBASE-LR4 application, a directly modulated DFB laser (DML) is widely used as a transmitter because it offers a low power consumption, small size, and low cost [3]–[7]. However, the continuous increase in traffic will inevitably require a further reduction in module size and cost. The transmitter module for 100GBASE-LR4 application employs four discrete DMLs, a lens and an optical filter, which makes it difficult to reduce the module size and assembly cost further.