Investigation of 60 Gb/s 4-PAM Using an 850 nm VCSEL and Multimode Fiber

We investigate 4-pulse-amplitude modulation (PAM) at data rates in the range of 50-60 Gb/s using a directly modulated 850 nm VCSEL and multimode fiber links up to 200 m. The channel conditions in which 4-PAM has performance advantages over traditional on-off keying are evaluated followed by experimental results at data rates of 56.7 Gb/s over distances up to 200 m using equalization and FEC, with a post-FEC bit error rate of 10
^-12
. The reported analysis is applicable to future Ethernet and Fibre Channel applications requiring 50 Gb/s serial data rates per lane over multimode fibers.