Modal Bandwidth Enhancement Through Launch Condition Optimization for High Data Rate VCSEL Transmission Over Multimode Fibers

Vertical-cavity surface-emitting laser (VCSEL)-based transmission over multimode fiber (MMF) has achieved data rates of 100G per lane and is progressing towards 200G/lane, which demands more modal bandwidth from MMF to ensure adequate transmission reach. We address the needs of higher modal bandwidth from the point of view of engineering VCSEL launch conditions. We explore the options for using subsets of 10 standard-based launch conditions by analyzing the measured encircled fluxes from commercial VCSEL transceivers over two options. By utilizing experimentally measured MMF data, we demonstrated a significant improvement in modal bandwidth with these options. The launch conditions also impact the wavelength dependence of modal bandwidth for VCSELs operating at wavelengths longer than 850 nm. We conducted detailed Monte Carlo simulation of the wavelength dependence of modal bandwidth over MMFs. For one launch condition option using a smaller area, the modal bandwidths are improved over the effective modal bandwidth (EMB), and favor very high data rate transmission by allowing the use of a smaller area photodetector.