Mode partition noise in 850 nm VCSELs

In high-speed 850 nm vertical cavity surface emitting lasers designed for 10 G Ethernet over 300 m of multimode fibre, mode partition noise (MPN) can impair the performance of the transmission link where the power budget is limited. A simple and practical method to evaluate the Ogawa k-factor from the power penalty is presented due to MPN using free space optical filters to vary the laser root mean square spectral width. k values that varied from 0.3 to 0.45 is reported. In addition, the previously reported improvement in power penalty is confirmed in the presence of polarisation mode selective filtering