Comparing the Dual-Mode VCSEL in OM4-MMF and GI-SMF Links for NRZ-OOK and 16-QAM-OFDM Transmissions

A dual-mode (DM) vertical-cavity surface-emitting laser (VCSEL) is investigated for carrying high-speed data transmission with either the non-return-zero on-off keying (NRZ-OOK) or the quadrature amplitude modulation-orthogonal frequency division multiplexing (QAM-OFDM) format. In both the back-to-back (BtB) and the 100-m transmission cases with using either the OM4 multimode fiber (OM4-MMF) or the graded-index single-mode fiber (GI-SMF), the mismatch between the core diameter of the lensed MMF pick-up head and the mode field of the DM-VCSEL output controls the coupled transverse mode number and decrease the modal dispersion effect. Using pre-emphasized NRZ-OOK data can compensate the SNR degradation to improve the BER to 5.6 × 10
⁻¹²
under BtB and 6.9 × 10
⁻¹⁰
after 100-m GI-SMF for the DM-VCSEL delivered NRZ-OOK data at 53 Gbit/s. For 16-QAM OFDM transmission, the pre-leveling algorithm shows better data compensation than the pre-emphasis algorithm in both BtB and the 100-m GI-SMF cases. With the pre-leveling compensation of the 16-QAM OFDM data encoded to the DM-VCSEL with a 0.4-dB/GHz slope, the DM-VCSEL allows 136 Gbit/s for BtB, 112 Gbit/s for 100-m OM4-MMF, and 92 Gbit/s for 100-m GI-SMF transmissions. The pre-emphasis NRZ-OOK and the pre-leveling 16-QAM OFDM data carried by the DM-VCSEL can be used in ultrahigh-speed intra-data-center links in the future.