Performance of quantum-dash mode-locked lasers (QD-MLLDs) for high-capacity coherent optical communications

Area of Science:

• Photonics
• Optical Communications
• Quantum Dash Lasers

Background:

• Quantum-dash mode-locked lasers (QD-MLLDs) are emerging as potential sources for optical frequency combs.
• Coherent optical communication systems demand stable, narrow linewidth laser sources.

Purpose of the Study:

• To evaluate QD-MLLDs as optical frequency comb sources for coherent optical communication.
• To compare QD-MLLD performance against conventional narrow linewidth lasers and commercial tunable laser assemblies.

Main Methods:

• Transmission of 64 quadrature amplitude modulation (QAM) signals at 80 GBd over 80 km of standard single-mode fiber (SSMF).
• Utilizing a silicon photonic (SiP) modulator with a 38.5 GHz bandwidth for high symbol rate transmission.
• Characterization of QD-MLLD comb line properties, including RF linewidth and usable comb lines.

Main Results:

• QD-MLLDs demonstrate performance comparable to conventional narrow linewidth lasers.
• Successful transmission of 80 GBd 64-QAM signals over 80 km SSMF, showcasing QD-MLLD phase noise characteristics.
• Achieved a maximum symbol rate of 104 GBd with 16-QAM and a net rate of 416 Gb/s per carrier using a SiP modulator after 80 km SSMF transmission.

Conclusions:

• QD-MLLDs are suitable for high symbol rate coherent optical communication systems.
• QD-MLLDs offer a competitive alternative to traditional laser sources, with potential as local oscillators and signal carriers.
• The distinct phase noise performance of QD-MLLDs enables robust high-speed data transmission.