112-Gb/s PAM4 Transmission Over 1 km of MMF With Mode-Field Matched Center- Launching in 850-nm Band

We evaluate possibility of utilizing the mode-field matched center-launching (MCL) technique in the 850-nm band. For this purpose, we realize the MCL technique by fusion-splicing the HI-780 pigtail fiber of the transmitter to the OM2-type transmission multi-mode fiber (MMF). The results show that we can achieve the high coupling efficiency of >92% by optimizing the splicing conditions such as the arc-discharge duration and fiber-push distance. We confirm that, in the case of utilizing the MCL technique, the frequency-response characteristics of the MMF link becomes almost identical to that of the single-mode fiber (SMF) link. As a result, we could demonstrate the successful transmission of 112-Gb/s four-level pulse amplitude modulation (PAM4) signal operating at 852 nm over 1 km of the OM2-type MMF by utilizing the MCL technique. The performance of this link is measured to be very stable even in the presence of the mechanical perturbations such as fiber bending and fiber shaking.