Photonic Crystal Structured Multi-Mode VCSELs Enabling 92-Gbit/s QAM-OFDM Transmission

The multi-mode vertical-cavity surface-emitting lasers (MM-VCSELs) with different photonic crystal (PhC) designs in core and cladding regions are compared for transmitting the complex formatted QAM-OFDM data over 100-m OM5 multi-mode fiber (MMF). Among the designs with using flat core/cladding (denoting as Coreflat/Cladflat) and/or PhC core/cladding (denoting as Corephc/Cladphc) for the MM-VCSEL, the Coreflat+Cladflat VCSEL with the highest threshold current and large emission aperture provides the highest differential quantum efficiency of 0.11 and output power of 2 mW, whereas the Coreflat+Cladphc2 VCSEL with two periods of cladding PhC reveals the lowest threshold current of 2 mA, the highest modulation bandwidth of 15 GHz, the lowest relative intensity noise peak of -126 dBc/Hz and background level of -143 dBc/Hz. After pre-compensation, the Coreflat+Cladphc2 VCSEL chip can achieve the highest OFDM bandwidth of 18 GHz for 72-Gbit/s transmission in the BtB case. With additionally adding 1 period of core PhC, the Corephc1+Cladphc2 VCSEL possesses a single-mode lasing spectrum to facilitate the suppression of modal dispersion after MMF propagation. Hence, the Corephc1+Cladphc2 VCSEL exhibits the same bit rate of 60 Gbit/s as compared to the Coreflat+Cladphc2 VCSEL after 100-m OM5-MMF. After improving the analog bandwidth for waveform synthesis, the data rate of Coreflat+Cladphc2 VCSEL can successfully deliver 76-Gbit/s and 72-Gbit/s single-band 16-QAM OFDM data streams for BtB and 100-m OM5 MMF conditions via the pre-leveling technology. To date, the ultimate raw data rate achieves 92-Gbit/s with employing the multi-band QAM-OFDM data format.