This paper will review the VCSEL performance requirements and link length limitations to support next generation 53Gbaud line rates with PAM-4 modulation for 100G per lane multi-mode optical links for both active optical cables and transceivers. VCSEL performance with bandwidth in excess of 25GHz and relative intensity noise lower than -145dB/Hz will be needed to enable this next generation of multi-mode links. VCSEL device performance and associated wear out life data will be included.
The development of robust next generation multi-mode VCSEL-based optical links requires an accounting of all penalties in the link. While limitations from fiber bandwidth can be overcome to a significant extent using equalization and forward error correction, noise in the link cannot be equalized. Measurements show that mode partition noise depends on launch condition, and the noise penalty can be decreased using devices with small k factor. Time and frequency domain characterization of mode power fluctuations shows that they occur primarily at frequencies below 5 GHz. These findings guide the development of VCSELs for 25GBaud PAM4 and higher bit rate applications.