25 Gbit/s transmission over 500 m multimode fibre using 850 nm VCSEL with integrated mode filter

An integrated mode filter in the form of a shallow surface relief was used to reduce the spectral width of a high-speed 850 nm vertical-cavity surface-emitting laser (VCSEL). The mode filter reduced the RMS spectral width from 0.9 to 0.3 nm for a VCSEL with an oxide aperture as large as 5 m. Because of reduced effects of chromatic and modal fibre dispersion, the mode filter significantly increases the maximum error-free (bit error rate 10^-12) transmission distance, enabling transmission at 25 Gbit/s over 500 m of multimode OM3 fibre.