Spatial investigation of transverse mode turn-on dynamics in VCSELs

Data transmission experiments with single-mode as well as multimode 850-nm vertical-cavity surface-emitting lasers (VCSELs) are carried out from a nea r-field point of view. Special attention is paid to important quantities li ke on/off-ratio and bit error rate (BER) A single-mode VCSEL oscillating on the fundamental LP01 mode shows no change in eye opening, on/off-ratio, an d BER at different lateral fiber coupling positions. In the case of a multi mode VCSEL oscillating both on the LP01 mode and LP11 donut mode, we observ e a significant lateral change in the on/off-ratio, which plays an importan t role in BER measurements.