Bandwidth enhancement equalization enabling a 40-Gbps PAM4 transmission via a 9.5-GHz photoreceiver

We demonstrate a 40-Gbps PAM4 optical system by employing a photoreceiver with bandwidth of only 9.5 GHz. Following 100 m multimode fiber, the BER of 1.8 × 10 −4 and 1.2 × 10 −4 after FFE and DFE equalizations are successfully achieved.