Mitigation of Mode Partition Noise in VCSEL-MMF Links by Optimizing Launch Conditions

The multimode characteristics of vertical cavity surface emitting laser (VCSEL) sources lead to mode partition noise (MPN) impairing high-speed multimode fiber (MMF) links. In this letter, we propose a low-cost and straightforward MPN mitigation scheme by optimizing the launch condition between the VCSEL and the MMF. The dependence of the MPN on launch conditions is theoretically assessed. Simulation shows that the mode power redistribution induced by rearranging the launch condition has great potential to reduce the MPN. Experiments are carried out to demonstrate the MPN reduction. In our case, using a 15- $\mu \text{m}$ radial offset between the VCSEL and the MMF, we observe efficient noise suppression in both the frequency domain and the time domain.