Historically optical links up to 100-300m distances are served by light emitting devices in the 850 nm spectral range in combination with multimode glass fibers (MMF). As the silicon scaling continues, a single channel data rate is to double each 24 months. Light-emitting diodes had to be replaced by vertical cavity surface emitting lasers (VCSELs) and the data rate increased from 100 Mb/s to 10 Gb/s. At higher data rates problems with further scaling evolved. To avoid the collapse an anti-waveguiding VCSEL cavity design was invented, applied, and presently serves data links operating up to 50-100 Gb/s per channel. Another requirement in data communication is the bandwidth density scaling, with the number of channels per link increasing approximately 5-fold each 10 years, while keeping a similar space for connectors. A coarse short-wavelength division multiplexing allowing 850 nm, 880 nm, 910 nm, and 940 nm wavelengths in a single MMF is introduced. The bandwidth density increase is also possible by using multicore fiber (MCF) coupled to on-chip VCSEL arrays. The data rates up to 224 Gb/s are already reached by 850nm VCSELs. At such data rates significant transmission distance over MMF is only possible by applying ultra-narrow spectrum VCSELs minimizing the chromatic dispersion effects. On-chip mini-arrays of oxide-confined VCSELs allow a high coupling efficiency to MMFs, a narrow spectrum, a high power, a significant transmission distance at high data rates. Coherent lasing in such arrays allow photon-photon resonance engineering aimed at modulation bandwidths ∼50-100 GHz.