Low-Power Consumption 28-Gb/s 80-km Transmission With 1.3-μm SOA-Assisted Extended-Reach EADFB Laser

We extend the transmission distance for 28-Gb/s optical links from 40 to 80 km in a single-mode fiber (SMF) in the 1.3-μm-wavelength window by using an intensity-modulation direct-detection scheme. To extend the link budget, and compensate for the optical loss of SMF, we try to increase the optical output power of an electroabsorption modulator integrated with distributed feedback (EADFB) laser. We apply a semiconductor optical amplifier (SOA)-assisted extended-reach EADFB laser (AXEL) to a 1.3-μm-wavelength light source. To increase the optical output power while using energy efficiently, we design the SOA length in terms of achieving a balance between the laser diode (LD) and the SOA length with a constant injection current of 160 mA. We fabricate an AXEL and an EADFB laser and compare their basic characteristics. By using the high-power AXEL, we achieve the first 28-Gb/s 80-km SMF transmission without the need for digital signal processing or an in-line optical amplifier. The AXEL consumes only 0.26 W and does not require any digital processing or an in-line amplifier and can, therefore, reduce the power needed for an optical network system by tens of watts.

I. Introduction

The increase in data traffic caused by changes in our daily lives (e.g., the use of smart phones and cloud computing) has required optical network systems to upgrade their data transmission capacities while suppressing any increase in their power consumption. In addition, the cost per unit of transmission capacity ($/bit) also needs to be reduced to cope with the continuous increase in data traffic. When we focus on power consumption and the cost of an optical network system, an intensity-modulation direct-detection (IM-DD) scheme is a better solution than a coherent scheme, because this configuration does not need an additional receiver circuit such as a digital signal processor (DSP).