## 5 Experimental Results  
Using the experimental setup shown in Figure 5 and described in Section 4, we make a fair comparison, showing the performance limits in terms of achievable data rates for short-reach optical interconnect applications. Our goal is to achieve a data rate that is as high as possible, even up to 60 Gbps/\(\lambda\) in the system that uses the implemented Kerr-OFC generated optical carriers for carrying IM/DD data. The received and sampled signal is processed offline after the reception, using a DSP routine that consists of a low-pass filter (LPF), a maximum variance timing recovery, post-equalization, and a BER counter. The LPF has a bandwidth of 0.6 times the Baud rate. That value was identified using the results data shown in Figure 7. It ensures the best possible performance after further processing. In such a case, we obtain BER as a function of the LPF\({}_{\text{BW}}\)/Baud rate from 0.4 to 0.8 for NRZ-OOK signals. Figure 6: End-to-end system calibration using the EAWG for the OB2B configuration: (**a**) phase response and (**b**) amplitude response. The post-equalization was used to improve signal quality; we use a DFE configuration with 33 feed-forward taps (FFT) and 15 feedback taps (FBT), as well as 16 taps are used as a reference. The adaptive DFE helps to overcome the inter-symbol interference ISI in the presence of noise and bandwidth limitations. As shown in Figure 7a, 40 Gbaud and 50 Gbaud signals are almost overlapping because DFE with both feed-forward (FF) and feedback (FB) taps due to the intensity fluctuations (power instability) of carrier (\(-1\)) cannot show performance improvements in terms of high baud rate. The initial weights of the equalizer are obtained using the training data with the normalized least-mean-square (NLMS) algorithm before applying other data. A total number of 1.2 million bits are used for BER counting. First, we analyze system performance without post-equalization. Afterward, we focus on improvements that the linear post-equalization can offer. We show BER curves and eye diagrams of the received NRZ-OOK signals after the 2 km transmission over the SMF link. In this paper, we consider the hard-decision forward error correction (HD-FEC) with 7% overheads (OH) with a pre-FEC BER threshold at 5 \(\times\) 10\({}^{-3}\)[35]. We use the conventional BER curves showing how pre-FEC BER values change with the received optical power (ROP). We assume that all errors can be corrected for the pre-FEC BER below that threshold. As one can see in Figure 8a, the worst-performing (based on the BER value) data channel is the carrier (\(-1\)) at 1548.485 nm, yet it is capable in providing the maximum bitrate of 50 Gbps. In this sub-figure, the 60 Gbps curve is not shown because due to extremely poor BER performance, i.e., it is way beyond our defined pre-FEC BER threshold of 5 \(\times\) 10\({}^{-3}\). The best performing (based on the BER) data channel is the pumping source carrier with a wavelength of 1551.737 nm depicted as a carrier (0). Without the post-equalization, the received 40 Gbaud and 50 Gbaud NRZ-OOK signals are mostly below the 7% HD-FEC limit for the Kerr-OFC generated carriers (\(-1\)), (0), and (\(+1\)); see Figure 8a-c. In those cases, the main limitations are a relatively low effective bandwidth of the electrical components, ISI, and the implementation penalty itself. Figure 7: BER versus \(\text{LPF}_{\text{bw}}\)/Baud rate for the IM/DD communication system operating on 400 GHz spaced carriers generated by microsphere Kerr-OFC: (**a**) \(\lambda\) = 1548.485 depicted as carrier \({}^{\prime\prime}\) –1”; (**b**) \(\lambda\) = 1551.737 depicted as carrier \({}^{\prime\prime}\)0”; (**c**) \(\lambda\) = 1554.992 depicted as carrier \({}^{\prime\prime}\)+1” provide NRZ-OOK signals up to 60 Gbps/\(\lambda\). To achieve higher data rates, a dispersion-induced power fading must be reduced, and signal equalization must be applied to reach the BER threshold of \(5\times 10^{-3}\).